WO2022239209A1 - Composite powder material, method for producing same, and electrode material - Google Patents

Abstract

Provided are a novel composite particle material of an MXene nanosheet and a carbon microbody, and a method for producing the same.　A composite particle material according to the present invention has 90-97 parts by mass of a sheet-shaped Ti₃Al_a(C_(1.0-x)N_x)₂ (0 ≤ x ≤ 0.03, a is more than 0.02) MXene and 3-10 parts by mass of a carbon microbody, and has an interdispersibility of 1.50-7.00 and a specific surface area of 75 m²/g or more.

Description

Composite powder material, manufacturing method thereof, and electrode material

The present invention relates to a novel composite particle material of MXene nanosheets and microparticles, a method for producing the same, and an electrode material using the composite particle material.

Conventionally, a particle material made of an MXene layered compound obtained by removing Al from a MAX phase ceramic powder such as Ti ₃ AlC ₂ which is a layered compound by acid treatment (in this specification, it is appropriately referred to as "MXene particle material" or " It is sometimes referred to as "MXene nanosheet", "layered compound particle material", or simply "particle material") (Patent Documents 1 to 4). These MXene layered compounds can store and release Na ions and Li ions in the void layer from which the Al layer has been removed, so they are used as negative electrode active materials for secondary batteries (storage batteries) and capacitors, and also have excellent conductivity. Therefore, it is expected to be applied to electromagnetic wave shield thin films and conductive thin films.

MAX phase ceramics are layered compounds, and the general formula is expressed as M _n+1 AX _n . In the formula, M is a transition metal (Ti, Sc, Cr, Zr, Nb, etc.), A is an A group element, X is C or [C _(1.0-x) N _x (0<x≦1.0)] , n is from 1 to 3.

Among them, when A is Al, the bond of MA is weaker than that of MX, so the Al layer is selectively removed by acid treatment. The present inventors have proposed a method of preparing MXene nanosheets by exfoliating them with a bead mill using micro-sized beads (Patent Documents 5 and 6).

Japanese Patent Application Laid-Open No. 2016-63171 JP 2017-76739 A U.S. Patent Application Publication No. 2017/0294546 U.S. Patent Application Publication No. 2017/0088429 Japanese Patent No. 6564553 Japanese Patent No. 6564552

Here, when MXene nanosheets are used in secondary batteries (storage batteries) and capacitors, not only MXene nanosheets but also acetylene black as a conductive aid are added and used. In order to improve battery characteristics, it is necessary to increase ion diffusibility and to smoothly move electrons to the current collector. Specifically, by exfoliating the nanosheets to a single layer level and appropriately reducing the size thereof, the specific surface area of the MXene and acetylene black composite particle material is increased, and the acetylene black is uniformly arranged between the nanosheets. is required. As a result of intensive studies, the inventors succeeded in obtaining a composite particle material of MXene nanosheets and carbon microparticles, which is effective as an ideal secondary battery (storage battery) negative electrode active material. In addition, if it is a microscopic object other than carbon microscopic objects, it is possible to obtain a new material by combining it with the MXene nanosheet, so in this specification, microscopic objects other than carbon microscopic objects are also subject to consideration. and

The present invention has been completed in view of the above circumstances, and the problem to be solved is to provide a novel composite particle material of MXene nanosheets and microparticles, a method for producing the same, and an electrode material using the composite particle material. do.

The composite particle material of the present invention that solves the above problems comprises 90 to 97 parts by mass of sheet-like Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≤x≤0.03, a is more than 0.02) MXene and 3 to 10 parts by mass of microparticles, a mutual dispersion degree of 1.50 to 7.00, and a specific surface area of 75 m ² /g or more. The interdispersion degree will be described in the embodiment section.

It is preferable that the average pore diameter is 7.0-20.0 nm and the pore volume is 0.10-0.50 mL/g.

The Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) MXene has an average thickness of 1.0 to 3.5 nm, It is preferable that the average size in the spreading direction of the sheet is 0.5 to 1.0 μm, and the primary particle diameter of the fine particles is 30 to 50 nm. Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) The interlayer distance of the (002) plane of MXene is 1.400 nm to 1.700 nm is preferably Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) MXene's (002) plane has a half width of 0.90° to 1 0.50° is preferred. It is preferable that the surface electric resistance is from 1.0Ω/□ to 100.0Ω/□.
_MXene with _a zeta potential of _{-25.0 mV} to _-30.0 mV and _- It is preferably composed of carbon particles with a voltage of 20.0 mV to -25.0 mV.

The negative electrode of the present invention that solves the above problems has the composite particle material of the present invention as a negative electrode active material.

The method for producing _a composite particle material of the present invention that solves the above problems is the _Ti3Ala (C( _{1.0 -x )} Nx) ₂ (0≤x≤0.03, a is greater than 0.02) MXene a stripping step of stripping to form a stripped product, an acid treatment step of treating the raw carbon fine particles in a mixed acid aqueous solution of sulfuric acid and nitric acid at 70 ° C. or higher for 10 minutes or more to obtain the carbon fine particles, and the stripped product and a mixing step of obtaining a mixture in which the carbon fine particles are dispersed in the second dispersion medium at a mass ratio of 90: 10 to 97: 3 and the exfoliated substance is dispersed in the second dispersion medium at a concentration of 11.5 to 17.0 mg / mL, from 100 rpm a step of intercalating an aqueous solution of lithium chloride with _{a shaker} at _a rotation speed of _{300 rpm} ; ₂ (0≤x≤0.03, a is greater than 0.02) and an aggregation step of obtaining a composite particle material of MXene and the carbon fine particles. In particular, the stripping step is preferably a step in which 99% or more of the MXene on a mass basis becomes the stripped product.

The composite particle material and the method for producing the same of the present invention have the above configuration, so that Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0 ≤ x ≤ 0.03, a is more than 0.02 ) It is possible to provide a composite particulate material in which MXene and microparticles are highly dispersed. Such _{a Ti3Ala} (C( _{1.0 -x )} Nx) ₂ (0≤x≤0.03, a is greater than 0.02) MXene and fine particles are highly dispersed, and a composite with a high specific surface area By adopting the particulate material as the negative electrode active material, it is possible to provide a negative electrode that can exhibit high performance when used in secondary batteries (storage batteries) and capacitors.

4 is an AFM image of a peeled product obtained in the peeling step of Example 1. FIG. 4 is an SEM photograph of a peeled product obtained in the peeling step of Example 1. FIG. 2 is the XRD profile of the MAX phase ceramics of Example 1, MXene after being subjected to an exfoliation process, and the composite powder material. 4 is a graph showing the cycle characteristics of Li-ion secondary batteries using the composite powder materials of Example 1 and Comparative Example 1 as electrode active materials. 1 is a graph showing charge-discharge curves at the 1st cycle and the 100th cycle of a Li-ion secondary battery using the composite powder material of Example 1 as an electrode active material. 1 is a SEM photograph of the composite powder material of Example 1. FIG. 4 is a SEM photograph of the composite powder material of Example 4. FIG. 4 is a SEM photograph of the composite powder material of Example 2. FIG. 4 is an SEM photograph of the composite powder material of Comparative Example 1. FIG. 4 is an SEM photograph of the composite powder material of Comparative Example 2. FIG. 4 is a graph showing the dependency of the specific surface area of the resulting composite powder material on the particle concentration of exfoliated material (MXene) in the aggregation step. FIG. 2 is a diagram showing the crystal structure of MAX phase ceramics presented to explain the crystal structure of MXene;

The composite particle material, the method for producing the same, and the electrode material of the present invention will be described in detail below based on embodiments. The composite particle material of the present embodiment has excellent electrical properties such as conductivity, and has a large void layer formed by removing the Al layer, so it is suitable for secondary batteries (Li-ion secondary batteries, Na ion secondary battery), active materials (especially negative electrode active materials) such as capacitors, electromagnetic wave shielding thin films, conductive thin film materials, and the like.
(Composite particle material)
The composite particle material of the present embodiment is a particle material obtained by combining thinned MXene and particulate or tube-like carbon microscopic bodies for application to electrode materials and the like. MXene exfoliated particulate material is obtained by exfoliating MXene, which is a powdery layered compound.

In this specification, when a plurality of upper limit values and lower limit values are set for a certain parameter, those upper limit values and lower limit values can be arbitrarily combined unless otherwise specified. The composite particle material of this embodiment is a composite particle material of MXene and microscopic bodies.

MXene contains 90 to 97% based on the sum of the mass of MXene and microscopic bodies, and the remaining 10% to 2% is microscopic bodies. The lower limits of the MXene content include 93%, 92%, and 90%, and the upper limits include 97%, 96%, and 95%.

The composite particulate material has a mutual dispersity of 1.50 to 7.00. The interdispersion degree is a value that defines the degree of dispersion between MXene and minute particles. When carbon particles are used as the particles, the degree of interdispersion is determined by Raman spectroscopic analysis of 100 randomly selected composite particle materials using a 532 nm wavelength laser with a peak height A of 400 cm ⁻¹ . The standard deviation calculated from the ratio (B/A) of the peak heights B at 1332 cm ⁻¹ and 1332 cm −1 is defined as the degree of interdispersion. The interdispersion degree of the composite particulate material can adopt lower limits of 1.50, 2.00, 2.50 and upper limits of 7.00, 6.00, 5.00. .

The composite particulate material has a specific surface area of 75 m ² /g or more. The specific surface area is measured by the BET method using nitrogen under the condition that pretreatment is performed in vacuum at 100° C. for 24 hours. As for the specific surface area of the composite particle material, 75 m ² /g, 77.5 m ² /g and 80 m ² /g can be adopted as lower limits, and 110 m ² /g, 107.5 m ² /g and 105 m 2 /g as upper limits. ² /g can be adopted. The composite particulate material preferably has an average pore diameter of 7.0-20.0 nm and a pore volume of 0.10-0.50 mL/g. The average pore diameter and pore volume were measured by the BET method using nitrogen under the condition that pretreatment was performed in vacuum at 100° C. for 24 hours.

MXene consists of _three layers of titanium and two layers of carbon, or _Ti3Ala (C( _{1.0 -x )Nx} ) ₂ (0≤x≤0), which is a layered compound in which part of the carbon is replaced with nitrogen. .03, a is greater than 0.02) MXene (hereinafter referred to as "MXene" as appropriate). MXene is preferably Ti ₃ Al _a (C _{( 1.0} - _x )N _x ) ₂ . Here, 0≤x≤0.03 and a is preferably greater than 0.02. The upper limit of a is preferably 0.05. In addition to these elements, it can have O, OH, and halogen groups as surface functional groups.

MXene is plate-like, leaf-like, flaky, sheet-like, etc., and is generically defined as sheet-like. In MXene, the stacking direction of layers of a layered compound is defined as "thickness", and the direction orthogonal to the thickness is defined as "sheet spreading direction". The average thickness of MXene is preferably 1.0 to 3.5 nm, more preferably 1.5 to 3.0 nm. The average thickness is calculated as the average of the values measured on 100 randomly selected particles. The size of the sheet can be measured by dropping a nanosheet onto a hydrophilized Si wafer and using SEM. The average size of the sheet in the spreading direction is preferably 0.5 to 1.0 μm, more preferably 0.5 to 0.75 μm. Measured by SEM for 100 randomly selected particles, where the maximum value in the direction orthogonal to the thickness is the “long side” and the minimum value is the “short side”, [(long side + short side) / 2 ] is taken as the average size in the spreading direction.

The interlayer distance of the (002) plane of MXene is preferably 1.400 nm to 1.700 nm. The interlayer distance of the void layer is the value obtained by subtracting the interlayer distance, which is the d value of the (002) plane in XRD of the corresponding MAX phase ceramic powder, from the interlayer distance, which is the d value of the (002) plane in XRD of the MXene nanosheet powder. By definition, 0.770 nm to 0.470 nm. The diameter of Li ion is 0.18 nm and the diameter of Na ion is 0.28 nm, and it can be used as a negative electrode active material for Na ion secondary battery as well as Li ion secondary battery. Since the interlayer distance of the (002) plane of the graphite powder used in the negative electrode active material of Li-ion secondary batteries is 0.33 nm, it cannot be used for Na-ion secondary batteries. This is the reason why it is expected as a Na-ion secondary battery. Here, the corresponding MAX phase ceramic powder is _a particle material composed of a material having a value of 1 in the composition _Ti3Ala (C( _{1.0 -x )} Nx) ₂ of MXene to be measured. be.

It is sufficient for the microscopic object to have a size on the order of nanometers, and being on the order of nanometers means that the length of the longest part of the length of the microscopic object is 100 nm or less. The fine particles preferably have a primary particle size of 100 nm or less, preferably 30 to 50 nm, particularly preferably 30 to 40 nm, and may be aggregates. The shape of the microscopic object is not limited, and spherical, sheet-like, tube-like, hollow, and irregular shapes can be exemplified.

In particular, the microscopic bodies preferably have electrical conductivity, and examples of conductive materials include carbon microscopic bodies made of carbon materials and metal microscopic bodies made of metal materials. As the fine carbon particles, it is preferable to use those having high conductivity such as acetylene black, ketschen black, carbon nanotubes, graphene, carbon fiber, graphite powder, and hard carbon powder. In addition to carbon microscopic bodies made of a carbon material, inorganic microscopic bodies made of other inorganic substances can also be used as the microscopic bodies. TiO ₂ , Al ₂ O ₃ , SiO ₂ and BaTiO ₃ having a primary particle size of 100 nm or less can be used as the inorganic fine particles.
(Manufacturing method of composite particle material)
The method for producing a composite particulate material of this embodiment includes a peeling step, a mixing step, an intercalation step, an aggregation step, and other necessary steps.
• Exfoliation step The exfoliation step is a step of exfoliating the layered MXene by colliding microbeads between the layers in a dispersion medium to obtain a nanosheet exfoliation. The resulting exfoliate becomes an exfoliate suspension suspended in the dispersion medium. This exfoliated material suspension can be directly subjected to the mixing step, or can be subjected to the mixing step after removing the dispersion medium. The method for obtaining layered MXene as a material is not particularly limited, but the following methods can be exemplified.

MXene is obtained by acid-treating a raw material consisting of Ti 3-layer MAX phase ceramic powder and partially dissolving the Al layer. An example of a method for manufacturing MXene will be described later as a pretreatment step. The raw material to be subjected to the peeling step can employ those having the same composition as the material constituting the aforementioned particulate material. The composition does not substantially change in the stripping process.

This particle material is acid-treated to dissolve part of Al to form MXene, which is mixed in a solvent containing water as a main component to form a mixture, and then subjected to high-speed rotation using beads of 10 μm to 300 μm. An exfoliated material suspension in which nanosheet-like exfoliated material of MXene is suspended is obtained by the exfoliation step of performing bead mill treatment.

The dispersion medium for the stripping step is not particularly limited, but preferably contains 50% by mass or more of water, and contains alcohols such as methanol, ethanol, and isopropanol, methyl ethyl ketone, acetone ketones, dimethylformamide, dimethyl sulfoxide, and the like. be able to. It is more preferable to make water 100% by mass.

The concentration of MXene in the mixture for the stripping process is not particularly limited, but can be about 10.0 mg/mL to 20.0 mg/mL. Although there are no particular restrictions on the liquid properties of the mixed liquid, the pH can be adjusted to approximately 6.0 to 8.0.

The specific bead mill processing in the peeling process will be explained. By centrifugal separation, a bead mill equipped with a mechanism for classifying fine beads and a slurry mixture can be used to separate them. The exfoliated material exfoliated by the bead mill treatment can be optionally separated from the mixture before exfoliation by centrifugation, and finally all MXene can be exfoliated.

For example, the lower limit of the bead size can be 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, and the upper limit can be 300 μm, 200 μm, 100 μm. When it is 10 µm or more, it is easy to classify beads and slurry. The use of beads of 300 μm or less allows delamination to proceed in preference to reducing the size of the particulate material. Any combination of these lower and upper limits can be adopted. If the size of the beads is in the proper range, the energy to be applied can be increased and the peeling can proceed preferentially.

The material of the beads is not particularly limited, but ceramics such as zirconia, alumina, and silicon nitride can be used. Partially stabilized zirconia, which has particularly high fracture toughness, is preferred. On the other hand, with commonly used bead mills that classify beads and slurries in micro-sized gaps using beads larger than 300 μm, size reduction of the particulate material progresses in preference to exfoliation. Ball milling, such as planetary ball milling with beads and balls greater than 300 μm, also favors exfoliation by reducing the size of the particulate material. As a result, only a part of the particles can be separated, and a part of the particles must be separated by centrifugal separation.

In addition, MXene has traditionally been exfoliated by ultrasonic irradiation. When the solvent is irradiated with ultrasonic waves, cavitation is generated, and due to the crushing of the cavitation, the layers constituting the layered compound are exfoliated by the mechanism of powder collision. However, even if water, which easily causes cavitation, is used, peeling progresses only partially. Furthermore, even if water is used, peeling progresses only in part, and it cannot be said that it is at a level that can be used in industry. Even in the method using a planetary ball mill, of course, the peeling is still part of the process, and the pulverization takes precedence, and the surface oxidation proceeds remarkably due to the temperature rise. For this reason, a method of exfoliating only a part by ultrasonic irradiation and collecting by centrifugal separation has been adopted.

A peripheral speed of 6 m/sec to 12 m/sec can be adopted for the peripheral speed in the peeling process. A peripheral speed of 8 m/sec to 10 m/sec is more preferable. If it is 6 m/sec or more, the peeling efficiency is good, and if it is 12 m/sec or less, the application of excessive energy is suppressed, and the temperature rise of the obtained particle material can be suppressed, so that the surface of the obtained particle material is oxidized. Progression can be suppressed, and electrical resistance can be lowered. A slurry feed rate of 100 mL/minute to 300 mL/minute can be adopted. A slurry particle concentration of 10.0 mg/mL to 20.0 mg/mL can be adopted.

If the concentration is 10.0 mg/mL or less, the production efficiency of the MXene nanosheets will be poor, and if the concentration is 20.0 mg/mL or more, peeling will not progress sufficiently, so this range is preferable.

The slurry temperature is preferably in the temperature range of 35°C or less. When the temperature is 35° C. or lower, surface oxidation can be suppressed, and the electrical resistance of the particulate material can be kept low.

40% to 80% can be used for the filling amount of beads. When it is 40% or more, the efficiency of stripping is improved, and when it is 80% or less, it becomes easy to classify beads and slurry. Whether or not the desired particle material containing many sheet-like particles has been produced can be determined by observation with SEM, TEM, or the like. In particular, the thickness of the particulate material can be determined by AFM analysis. The particulate material obtained in the peeling step can be used after being classified by a method such as centrifugation, if necessary. Optimal conditions in the peeling process vary depending on the size of the apparatus, so these numerical values are not limited.

It is preferable that 98% or more of the MXene on a mass basis is turned into the exfoliated material by the bead mill treatment, more preferably 99% or more of the exfoliated material, and still more preferably 100% of the exfoliated material. When the peeling process is completed under the condition that all the MXene becomes the peeled substance, it becomes possible to use the MXene which is not peeled off as it is in the mixing process without removing it. When removing MXene other than exfoliated matter, it can be separated by centrifugation, filtration, or the like.

The obtained exfoliated MXene preferably has a zeta potential of -25.0 mV to -30.0 mV in water of pH 6 to pH 8.

Regarding the chemical composition of the MXene nanosheets, the amounts of Al, C, and N were calculated using the atom% of Ti, Al, C, and N, with Ti being 3. For chemical analysis, weigh the sample in a platinum dish, add nitric acid + sulfuric acid + hydrofluoric acid, heat (about 120 ° C) to dissolve, and then heat at a high temperature (300 ° C) to mix nitric acid and hydrogen fluoride. A sample solution (sulfuric acid) was prepared by removing the acid, and the prepared sample solution was appropriately diluted and quantitatively analyzed by ICP.
Acid treatment step The acid treatment step is a step of treating the raw carbon microparticles with a mixed acid solution of sulfuric acid and nitric acid to obtain highly hydrophilic carbon microparticles. Examples of raw carbon fine particles include acetylene black, ketschen black, carbon nanotube, graphene, carbon fiber, graphite powder, and hard carbon powder. Acetylene black, Ketsujen black, and carbon nanotubes are more preferred from the viewpoint of conductivity, and acetylene black is more preferred from the viewpoints of both conductivity, purity, and price.

In the acid treatment step, a suspension of carbon microparticles suspended in the mixed acid is obtained, which can be used as it is in the mixing step, or the mixed acid can be washed repeatedly with water or the like to remove as much as necessary and used as carbon microparticles. can also Washing can be performed until the pH of the washing solution reaches about 6, and further until the pH reaches about 6.5, 7, or 8.

Through this treatment, functional groups such as COOH groups and CO groups are introduced to the surface of the carbon microparticles to make them hydrophilic. The carbon microparticles after treatment become a carbon microparticle suspension dispersed in the mixed acid. It does not matter whether it is performed between the acid treatment process and the stripping process.

The treatment temperature is preferably 70°C or higher. In particular, it is preferable to set the temperature to 95° C. or lower so as not to cause boiling. The treatment time is not particularly limited, but hydrophilization can be ensured by treatment for 10 minutes or longer. Stirring or ultrasonic irradiation can be performed during the treatment. After the treatment, it may be subjected to the mixing step as it is, or the acid may be neutralized or separated. If the acid is neutralized or separated and the pH reaches a predetermined value or higher, the fine carbon particles aggregate, so neutralization can be carried out to the extent that the pH does not reach the predetermined value. As a method of separating the acid, a method of separating the solid content by a classification operation such as centrifugation can be exemplified.

The mixing ratio of sulfuric acid and nitric acid can be about 4:1 to 1:1, preferably about 3:1 to 3:2 by volume. The concentration of the mixed acid can be about 42% to 96%, preferably about 90.0% to 95.0%.

The resulting hydrophilic carbon microparticles preferably have a zeta potential of -20.0 mV to -25.0 mV in pH 7 water. The zeta potential becomes negative because COOH and CO are adsorbed as functional groups. If the absolute value is smaller than -20.0 mV, the dispersibility in water deteriorates and the interdispersion degree of the composite particle material increases. If the absolute value becomes larger than -25.0 mV, the conductivity deteriorates.
・Mixing process In the mixing process, the mass ratio of the exfoliated matter and the carbon particles is 90:10 to 97:3, the concentration of the exfoliated matter is 11.5-17.0 mg/mL, and water is contained in an amount of 50% by mass or more. It is a step of obtaining a mixture dispersed in a second dispersion medium. More preferably, the second dispersion medium contains 100% by mass of water. By including other substances in the mixture, those substances can also be incorporated into the composite particulate material. In particular, coexistence of Li ions and Na ions allows these ions to be inserted into the MXene layer forming the exfoliation.

The mixture contains exfoliate at a concentration of 11.5-17.0 mg/mL. The second dispersion medium may be the same as or different from the dispersion medium used in the peeling process and the solvent that can be used in other processes. When the exfoliated material suspension obtained in the exfoliation step is directly subjected to the mixing step, the second dispersion medium contains the dispersion medium used in the exfoliation step. The reason for limiting the concentration of MXene particles in the composite slurry to 11.5-17.0 mg/mL is that if it falls below 11.5 or exceeds 17.0, the specific surface area of the composite particle material obtained in the aggregation step described later This is because the

It is preferable to intercalate chlorine and lithium ions by adding an aqueous solution of lithium chloride to the mixture and stirring the mixture with a shaker at a rotation speed of 100 rpm to 300 rpm for 1 hour to 6 hours. The amplitude of the shaker is preferably 40 mm or more. 5.3 g of lithium chloride in a ratio of 30 g of pure water can be completely dissolved by stirring with a shaker at a rotation speed of 100 rpm to 300 rpm for 1 hour or more. is preferably added to a suspension of The amplitude of the shaker at that time is preferably 40 mm to 45 mm. For the acid-treated carbon microparticles, a predetermined amount of carbon microparticles was added to pure water, stirred for 1 hour or longer with a shaker at a rotation speed of 100 rpm to 300 rpm, and the suspension was added to the mixture to break up the aggregates. Mixing is preferred. The amplitude of the shaker at that time is preferably 40 mm to 45 mm.
Aggregation step The aggregation step is a step of increasing the pH of the mixture obtained in the mixing step to aggregate the composite particle material of the exfoliated matter and the carbon fine particles contained in the mixture into aggregates. The pH is raised by adding an alkaline substance or by removing or diluting an acidic substance. It is preferable to increase the pH by adding the alkaline aqueous solution in a few seconds and stirring with a shaker at a rotation speed of 100 rpm to 300 rpm within 1 hour. The amplitude of the shaker at that time is preferably 40 mm to 45 mm.

Alternatively, it can be done by adding a highly hydrophobic organic solvent with a small dielectric constant.

The obtained agglomerate is dried and then brought into a desired state by an appropriate operation such as pulverization, whereby the composite particle material of the present embodiment having an appropriate particle size distribution can be obtained. The proper state is the state of the composite particulate material of this embodiment described above. The method for drying the aggregates is not particularly limited. For example, aggregates can be separated by classification operations such as centrifugation and filtration, and then dried. After separating the agglomerates, one or more washes can be carried out, if desired. Washing can be performed with water or the like.
Drying is a process of removing water adsorbed on the surface of the composite particulate material and water present between layers in the crystals. After washing the aggregates three times with ethanol or isopropyl alcohol, it is preferable to air-dry them. Alternatively, it is preferable to spray dry an ethanol or isopropyl alcohol suspension in nitrogen. In order to remove the water between the layers in the crystal, it is preferable to dry the crystal in a vacuum at a temperature in the range of 100° C. to 200° C. for 6 to 24 hours. By appropriately selecting the process conditions, the surface oxidation of MXene and carbon particles can be suppressed, and the surface electrical resistance of the obtained composite particle material can be kept low.
-Other necessary steps Other necessary steps are not particularly limited, but a pretreatment step can be exemplified. The pretreatment step is an example of a method for manufacturing MXene. For example, a mixed raw material of TiC, TiN, Al, and Ti is pressurized in the range of 1 ton/cm ² to 3 ton/cm ² by CIP or uniaxial pressure, or pressurized. Ti ₃ Al(C _1-x N _x ) ₂ (0≦x<1), which is a high-purity Ti 3-layer MAX phase ceramic, is produced by heat treatment in an inert atmosphere at 1400° C. to 1600° C. or less. can be exemplified. Alternatively, it can be produced by contacting the MAX phase ceramic powder with an acidic substance at a temperature controlled at 20° C. to 30° C. to remove part of the Al element contained in the MAX phase ceramic powder.

The raw material to be subjected to the pretreatment step is Ti ₃ Al _a [C _(1-x) N _x ] ₂ for the Ti3 layer, MAX phase ceramics having a composition represented by (a = 1, 0 ≤ x < 1) powder. Furthermore, the amount of Al to be removed is adjusted so that the amount of Al (corresponding to x) in the MAX phase ceramic powder produced by acid treatment with an acidic substance remains at a level exceeding 0.02. In addition, it is possible to remove all the Al, and in that case, it is preferable not to proceed the acid treatment beyond the removal of the Al.

The amount of Al to be removed depends on the contact time with the acidic substance (acid aqueous solution, etc.) (the longer the time, the more removed), the concentration of the acidic substance (the higher the concentration, the more removed), It can be adjusted by changing the amount of acidic substance (the greater the absolute amount of acidic substance, the greater the amount that can be removed) and the contact temperature (the higher the temperature, the greater the amount removed).

The MAX-phase ceramic powder (A element is Al), which is a layered compound, is subjected to an acid treatment to remove part of the Al to form a layered compound having void layers that constitute the particle material. As the acid for removing part of the Al layer, an acidic substance in which hydrofluoric acid and hydrochloric acid are combined is employed. In order to achieve a combination of hydrofluoric acid and hydrochloric acid, it is preferable to mix a hydrofluoric acid salt (KF, LiF, etc.) with hydrochloric acid to obtain a mixture of hydrofluoric acid and hydrochloric acid.

In particular, aqueous solutions of these acids are used as acidic substances. The mixed concentration of hydrofluoric acid and hydrochloric acid formed when the fluoride salt is completely dissociated is not particularly limited. As for the concentration of hydrofluoric acid, the lower limit is about 1.7 mol/L, 2.0 mol/L, and 2.3 mol/L, and the upper limit is about 2.5 mol/L, 2.6 mol/L, and 2.7 mol/L. can. The concentration of hydrochloric acid can be about 2.0 mol/L, 3.0 mol/L and 4.0 mol/L with lower limits and about 13.0 mol/L, 14.0 mol/L and 15.0 mol/L with upper limits. .

The mixing ratio (molar ratio) of hydrofluoric acid and hydrochloric acid formed when it is assumed that the fluoride salt is completely dissociated is not particularly limited, but the lower limit of hydrofluoric acid is 1:13, 1:12, 1:1: 11. About 1:5, 1:6 and 1:7 can be adopted as the upper limit. The concentrations and mixing ratios of hydrofluoric acid and hydrochloric acid shown here can be used in arbitrary combinations. The acid treatment temperature is preferably 20°C to 30°C. 20°C to 25°C is more preferred.
(Electrode material)
The electrode material of the present embodiment is a material that can be suitably used for secondary batteries. In particular, since it is possible to insert and remove Li ions and Na ions between layers, it can be suitably used as an electrode active material. Moreover, it can also be used as a conductive aid because of its conductivity. Effective for lithium secondary batteries and sodium secondary batteries. Lithium ions and sodium ions are stored and desorbed in the void layer from which the Al layer has been removed by acid treatment.

Here, we will use a lithium secondary battery as an example. The electrode has an active material layer containing an active material made of the composite particle material of the present embodiment, and a current collector made of a thin metal plate or the like and having an active material layer made of the active material formed on the surface thereof. A binder may be included to form the active material layer. Moreover, the active material layer can contain an active material other than the composite particle material of the present embodiment, a conductive auxiliary agent, and the like, if necessary. As the binder, a commonly used binder such as carboxymethyl cellulose, polyvinylidene fluoride, styrene-butadiene rubber, polyvinylpyrrolidone, polyvinyl alcohol, or any other binder that can be used can be used. Acetylene black, ketschen black, carbon nanotube, graphene, carbon fiber, graphite powder, hard carbon powder and the like can be used as the conductive auxiliary agent.

The composite particle material and the method for producing the same of the present invention will be described in detail below based on examples.
(Example 1)
・Pretreatment process TiC powder (TI-30-10-0020, Rare Metallic) 12.3 g, Ti powder (TIE07PB 3N, Kojundo Chemical) 4.9 g, Al powder (ALE15PB 3NG, Kojundo Chemical) 2.8 g was ball-mill mixed in isopropanol (IPA) for 12 hours, and the IPA was removed by an evaporator to obtain a uniformly mixed dry powder.

Using a graphite resistance furnace, the uniformly mixed dry powder was placed in an alumina crucible and sintered in an Ar stream at 1450° C. for 2 hours to obtain Ti ₃ AlC ₂ as MAX phase ceramics. The resulting Ti ₃ AlC ₂ was coarsely pulverized using a mortar and pestle, and then subjected to ball mill pulverization using 5 mm zirconia balls in IPA for 24 hours. Then, planetary ball mill pulverization (200 rpm, 15 minutes three times) using 0.5 mm zirconia balls was performed to obtain a suspension. IPA was removed from the suspension with an evaporator to obtain Ti ₃ AlC ₂ powder pulverized to about 3 μm.

Prepare an acid aqueous solution by adding 18 g of LiF to 300 mL of concentrated HCl, add 10 g of Ti ₃ AlC ₂ powder while cooling with ice, and stir with a magnetic stirrer for 24 hours under an environment controlled at 10 to 20 ° C. By stirring _, the Al was etched away to obtain a particulate material _consisting of _{Ti3Al0.02C2MXene} . After etching, it was washed with water until the pH reached about 6, and finally water was replaced with ethanol. This operation resulted in a raw suspension of the particulate material suspended in ethanol.

The particle concentration in the raw material suspension was measured, and water was added so that the particle concentration of Ti ₃ Al _0.02 C ₂ MXene was 16.9 mg/mL.
・Exfoliation process Ti ₃ Al _0.02 C ₂ was obtained by processing this raw material suspension in a bead mill with a ZrO ₂ bead diameter of 50 μm under the conditions of a slurry feed rate of 150 mL/min and a ZrO ₂ bead filling amount of 80%. An exfoliate consisting of MXene was produced. By repeating this treatment three times, almost all of the particle material composed of Ti ₃ Al _0.02 C ₂ MXene contained in the raw material suspension became exfoliated matter, and an exfoliated matter suspension containing the exfoliated matter was obtained. .

The resulting exfoliated material suspension was dropped onto a piranha-treated Si substrate (immersed in a mixed solution of H ₂ SO ₄ :H ₂ O ₂ =3 parts by volume:1 part by volume) and subjected to AFM analysis. An AFM image is shown in FIG. 100 exfoliated exfoliated products (nanosheets) were randomly sampled, and the average value of the thickness measured by AFM was obtained and shown in Table 1. Furthermore, the result of SEM observation is shown in FIG. 100 exfoliated products were randomly selected, and the vertical (maximum diameter in the direction perpendicular to the thickness direction) and horizontal (direction perpendicular to the vertical and thickness directions) dimensions were measured from the SEM photograph, and the average value was calculated. Table 1 shows the average value of the size of 100 exfoliated objects.

XRD measurement was performed on each of the powder of Ti ₃ AlC ₂ , which is MAX phase ceramics, and the exfoliated material (nanosheet of Ti ₃ Al _0.02 C ₂ MXene), and the results are shown in FIG. Focusing on the d value of the (002) plane from the XRD profile, Table 5 shows the interlayer distance.

The peeled matter was measured for zeta potential in water at pH 7.0, and the results are shown in Table 6 together with the specific surface area of the composite particle material described later.
・Acid treatment process As a method for acid treatment of acetylene black as fine carbon particles, 100 parts by mass of a mixed acid in which sulfuric acid (98% by mass) and nitric acid (68% by mass) are mixed at a volume ratio of 3:1 is mixed with 1 part of acetylene black. 0 parts by mass was added, and the mixture was immersed for 10 minutes in an environment of 85°C. Then, it was washed with water until the pH reached about 6.0, and then the water was replaced with IPA. It was air-dried to obtain a hydrophilic acetylene black powder. FTIR analysis detected COOH and CO groups as surface functional groups. The measured zeta potential at pH 7.0 in water was -22.5 mV. Acetylene black was added to 10 mL of pure water in an amount of 5% by mass based on the Ti ₃ Al _0.02 C ₂ MXene nanosheets, and aggregates were crushed with a shaker under the conditions of 140 rpm and amplitude of 45 mm for 24 hours to prepare a hydrophilic acetylene black slurry.

Hydrophilic acetylene black slurry was dropped onto a hydrophilized Si wafer and observed by SEM. 100 primary particles were arbitrarily observed, and the vertical and horizontal dimensions were measured, and the average primary particle diameter was 33 nm.
・Mixing step To 220 mL of the exfoliated material suspension obtained in the exfoliating process, 5.3 g of lithium chloride powder and acetylene black powder acid-treated in the acid treatment process were added to the exfoliated material (Ti ₃ Al _0.02 C ₂ MXene) as a reference. After adding 5% by mass, the mixture was uniformly stirred for 5 hours with a shaker at 140 rpm and an amplitude of 45 mm. Acetylene black was added in a state of being dispersed in 10 mL of water as described above. After uniform stirring, an aqueous solution obtained by dissolving 5.3 g of lithium hydroxide in 30 mL of pure water was completely dissolved in advance with a shaker at 140 rpm and an amplitude of 45 mm for 24 hours. was stirred for 1 hour under the conditions of After that, it was washed with water once, replaced with IPA three times, and air-dried to obtain a composite particle material consisting of Ti ₃ Al _0.02 C ₂ MXene flakes and acetylene black powder. This method of mixing together the exfoliated matter and the carbon microparticles together with a substance that generates chloride ions (lithium chloride in this embodiment) is referred to as method A. The concentration of exfoliate in the mixture in the aggregation step corresponds to 13.2 mg/mL.

For the obtained composite particle material, the results of XRD measurement are shown in Fig. 3, and the results of SEM observation are shown in Fig. 6. After vacuum drying at 100° C. for 24 hours, the specific surface area, average pore diameter, and average pore volume were measured by the BET method using nitrogen. Table 2 and FIG. 11 show the results. Further, Table 5 shows the interlayer distance and half width of the (002) plane of MXene calculated from the XRD measurement for the obtained composite particle material together with the interlayer distance and half width of exfoliated MXene.

Furthermore, the obtained composite particle material was subjected to Raman spectroscopic analysis using a laser with a wavelength of 532 nm. The laser irradiation conditions were such that exfoliated substances (MXene) contained in the composite particle material were not oxidized to precipitate anatase, and the laser was measured in the range of 100 cm ⁻¹ to 2000 cm ⁻¹ .

The vibration due to the functional groups adsorbed to the titanium atoms of the exfoliated Ti ₃ Al _0.02 C ₂ MXene is 230 to 470 cm ⁻¹ (hereinafter, the peak appearing at 400 cm ⁻¹ among the peaks appearing in this range is adopted as a representative, “ A peak”), the vibration due to the functional groups adsorbed on the carbon atoms appears near 580 cm ⁻¹ . On the other hand, for acetylene black, the SP ³ hybrid orbital carbon appears at 1332 cm ⁻¹ (hereinafter referred to as “B peak”), and the SP ² hybrid orbital carbon appears at 1500 to 1600 cm ⁻¹ .

The peak intensity was calculated for these A and B peaks. The peak intensity was calculated from the peak height, and the B/A value was calculated. 100 randomly selected composite particle materials were analyzed, the B/A value was calculated, and the standard deviation of these values was defined as the interdispersion degree of the composite particle material. Table 3 shows the results. A smaller interdispersion index means more uniform dispersion.

The obtained composite particle material was treated in vacuum at 100° C. for 5 hours, then uniaxially pressed in a φ10 mm mold at a pressure of 0.5 kg/cm ² , and then at a pressure of 1.0 ton/cm ² . Table 4 shows the results of surface electrical resistance measured by the four-probe method using a copper wire of φ0.1 mm using the CIP-treated green compact.
・Lithium-ion battery A CR-2025 type coin cell was prepared and the battery characteristics were investigated. The composite particle material of Example 1 was used as an electrode active material, acetylene black as a conductive auxiliary agent, and polyvinylidene fluoride (PVDF) as a binder in N-methylpyrrolidone (NMP) at a mass ratio of 80:10:10. and mixed using a mortar and pestle to obtain an electrode mixture paste. This paste was applied to one side of a Cu foil as a current collector, and dried in vacuum at 120° C. for 24 hours. The electrolytic solution used was ethylene carbonate (EC):dimethyl carbonate (DMC):diethyl carbonate (DEC)=1:1:1 (volume ratio) in which LiPF ₆ was dissolved as an electrolyte at a concentration of 1M. A lithium foil was used as the counter electrode. All these operations were performed under an Ar atmosphere (H ₂ O less than 0.1 ppm, O ₂ less than 0.1 ppm). A charge-discharge cycle test was performed for 300 cycles under the condition of 1C. The obtained battery characteristic results are shown in FIGS. 4 and 5. FIG.
(Example 2)
A composite particle material of Ti ₃ Al _0.02 C ₂ MXene and acetylene black was prepared in the same manner as in Example 1, except that the amount of acid-treated acetylene black added was 10% by mass with respect to the exfoliated product (MXene). of the composite particle material. SEM observation was performed in the same manner as in Example 1, and the results are shown in FIG. The BET specific surface area, average pore diameter, and average pore volume were measured in the same manner as in Example 1, and are shown in Table 2. The interdispersion index was calculated in the same manner as in Example 1 and shown in Table 3. The surface electrical resistance of the resulting composite particle material was measured in the same manner as in Example 1 and is shown in Table 4.
(Example 3)
A composite particle material of Ti ₃ Al _0.02 C ₂ MXene and acetylene black was prepared in the same manner as in Example 1 except that the amount of acid-treated acetylene black added was 3% by mass with respect to the exfoliated product (MXene). of the composite particle material. The BET specific surface area, average pore diameter, and average pore volume were measured in the same manner as in Example 1, and are shown in Table 2. The interdispersion index was calculated in the same manner as in Example 1 and shown in Table 3. The surface electrical resistance of the resulting composite particle material was measured in the same manner as in Example 1 and is shown in Table 4.
(Example 4)
In the same manner as in Example 1, an exfoliate suspension and acid-treated acetylene black were prepared. Acetylene black was added to 220 mL of the exfoliated material suspension at 5% by mass based on the mass of the exfoliated material, and after uniform stirring for 5 hours at 140 rpm and an amplitude of 45 mm with a shaker, lithium hydroxide was added to 30 mL of pure water. The dissolved aqueous solution was added and uniformly stirred for 1 hour with a shaker at 140 rpm and an amplitude of 45 mm. Thereafter, a composite particle material of this embodiment was prepared in the same manner as in Examples. Method B is a method of aggregating with an alkaline aqueous solution without mixing the exfoliated matter and a substance that generates chlorine ions together with the carbon microparticles, as in Method A.

FIG. 8 shows the result of SEM observation of the obtained composite particle material. Table 2 and FIG. 11 show the results of measuring the BET specific surface area, average pore diameter distribution, and average pore volume in the same manner as in Example 1. Table 3 shows the results of calculating the degree of interdispersion in the same manner as in Example 1. Further, Table 5 shows the interlayer distance and half width of the MXene (002) plane calculated from the XRD measurement for the obtained particle material.
(Example 5)
In Example 1, Ti ₃ Al _0.02 C ₂ MXene was used in the same manner as in Example 1 except that the concentration of exfoliated substances in the mixture in the aggregation step was 13.2 mg/mL, whereas it was 15.5 mg/mL. and acetylene black were prepared as the composite particle material of this example. The results of measuring the BET specific surface area in the same manner as in Example 1 are shown in FIG. Table 3 shows the results of calculating the degree of interdispersion in the same manner as in Example 1.
(Example 6)
TiC powder (TI-30-10-0020, Rare Metallic) 11.9 g, TiN powder (TN-30-10-0020, Rare Metallic) 0.38 g, Ti powder (TIE07PB 3N, Kojundo Chemical)4. Ti ₃ Al(C _0.97 N _0.03 ) ₂ as MAX phase ceramics was obtained in the same manner as in Example 1, except that 9 g of Al powder (ALE15PB 3NG, Kojundo Chemical) was 2.8 g. Acid treatment and peeling were performed in the same manner as in Example 1. The zeta potential at pH 7 in water was measured in the same manner as in Example 1 and is shown in Table 6. Acetylene black was acid-treated in the same manner as in Example 1 to prepare a composite particle material, and the BET specific surface area was measured in the same manner as in Example 1. Table 6 shows the results. Table 4 shows the surface electrical resistance.
(Comparative example 1)
Exfoliate suspension was prepared in the same manner as in Example 1. An aqueous solution prepared by dissolving lithium hydroxide in 40 mL of pure water was added to 220 mL of the exfoliated material suspension, and the mixture was stirred for 1 hour at 140 rpm with a shaker to prepare a mixed suspension. As in Example 1, the exfoliate concentration in the mixture was 13.2 mg/mL. It was washed with water once, replaced with IPA three times, and air-dried. A powder obtained by adding 10% by mass of acetylene black agglomerated powder based on the mass of the exfoliated material was stirred in NMP with a mortar and pestle, and vacuum-dried at 100 ° C. for 24 hours to obtain a composite particle material of the exfoliated material and acetylene black. It was prepared as a composite particle material of this comparative example. A SEM photograph of the composite particulate material is shown in FIG. Table 2 shows the results of measuring the BET specific surface area, average pore diameter distribution, and average pore volume in the same manner as in Example 1. Table 3 shows the interdispersion index. Table 4 shows the surface electrical resistance. FIG. 4 shows the results of measuring the battery characteristics in the same manner as in Example 1.
(Comparative example 2)
FIG. 10 is an SEM photograph of a composite particle material of this comparative example prepared in the same manner as in Example 1 except that the acetylene black powder to be added was used without performing the acid treatment step shown in Example 1. shown in Table 2 shows the results of measuring the BET specific surface area, average pore diameter, and average pore volume in the same manner as in Example 1. Table 3 shows the measurement results of the degree of interdispersion.
(Comparative Example 3)
A composite particulate material of this comparative example was prepared in the same manner as in Example 1, except that the bead mill treatment was performed in ethanol as the peeling step. Table 1 shows the results of measuring the average thickness and average size of the exfoliated material in the same manner as in Example 1. Table 2 shows the results of measuring the specific surface area, average pore diameter, and average pore volume. Table 3 shows the interdispersion index.
(Comparative Example 4)
In Example 1, the concentration of exfoliated matter in the mixture in the aggregation step was 13.2 mg/mL, while the concentration was 11.0 mg/mL. A material was prepared and used as the composite particle material of this comparative example. The results of measuring the BET specific surface area in the same manner as in Example 1 are shown in FIG.
(Comparative Example 5)
In Example 1, the concentration of exfoliated substances in the mixture in the aggregation step was 13.2 mg / mL, while the concentration was 5.0 mg / mL. A material was prepared and used as the composite particle material of this comparative example. The results of measuring the BET specific surface area in the same manner as in Example 1 are shown in FIG.
(Comparative Example 6)
In Example 1, the concentration of exfoliated matter in the mixture in the aggregation step was 13.2 mg / mL, while it was 17.6 mg / mL. A material was prepared and used as the composite particle material of this comparative example. The results of measuring the BET specific surface area in the same manner as in Example 1 are shown in FIG.
(Comparative Example 7)
In Example 1, the concentration of exfoliated substances in the mixture in the aggregation step was 13.2 mg / mL, while the concentration was 26.5 mg / mL. A material was prepared and used as the composite particle material of this comparative example. The results of measuring the BET specific surface area in the same manner as in Example 1 are shown in FIG.
(Comparative Example 8)
TiC powder (TI-30-10-0020, Rare Metallic) 11.7 g, TiN powder (TN-30-10-0020, Rare Metallic) 0.64 g, Ti powder (TIE07PB 3N, Kojundo Chemical)4. Ti ₃ Al(C _0.95 N _0.05 ) ₂ as MAX phase ceramics was obtained in the same manner as in Example 1, except that 9 g of Al powder (ALE15PB 3NG, Kojundo Chemical) was 2.8 g. Acid treatment and peeling were performed in the same manner as in Example 1. Acetylene black was acid-treated in the same manner as in Example 1 to prepare a composite particle material, and the BET specific surface area was measured in the same manner as in Example 1.
(Comparative Example 9)
TiC powder (TI-30-10-0020, Rare Metallic) 11.1 g, TiN powder (TN-30-10-0020, Rare Metallic) 1.3 g, Ti powder (TIE07PB 3N, Kojundo Chemical)4. Ti ₃ Al(C _0.90 N _0.10 ) ₂ as MAX phase ceramics was obtained in the same manner as in Example 1 except that 9 g of Al powder (ALE15PB 3NG, Kojundo Chemical) was used and 2.8 g. Acid treatment and peeling were performed in the same manner as in Example 1. Acetylene black was acid-treated in the same manner as in Example 1 to prepare a composite particle material, and the BET specific surface area was measured in the same manner as in Example 1.
(Comparative Example 10)
TiC powder (TI-30-10-0020, Rare Metallic) 10.4 g, TiN powder (TN-30-10-0020, Rare Metallic) 1.9 g, Ti powder (TIE07PB 3N, Kojundo Chemical)4. Ti ₃ Al(C _0.85 N _0.15 ) ₂ as MAX phase ceramics was obtained in the same manner as in Example 1 except that 9 g of Al powder (ALE15PB 3NG, Kojundo Chemical) was used and 2.8 g of Al powder. Acid treatment and peeling were performed in the same manner as in Example 1. Acetylene black was acid-treated in the same manner as in Example 1 to prepare a composite particle material, and the BET specific surface area was measured in the same manner as in Example 1.
(Comparative Example 11)
TiC powder (TI-30-10-0020, Rare Metallic) 9.2 g, TiN powder (TN-30-10-0020, Rare Metallic) 3.2 g, Ti powder (TIE07PB 3N, Kojundo Chemical)4. Ti ₃ Al(C _0.75 N _0.25 ) ₂ as MAX phase ceramics was obtained in the same manner as in Example 1, except that 9 g of Al powder (ALE15PB 3NG, Kojundo Chemical) was 2.8 g. Acid treatment and peeling were performed in the same manner as in Example 1. Acetylene black was acid-treated in the same manner as in Example 1 to prepare a composite particle material.

(result)
As is clear from Table 1, it was found that the thickness of the peeled material increased and the size of the peeled material decreased when only water-free ethanol was used as the dispersion medium in the peeling process. It was found that as the amount of water increased, the exfoliate thickness decreased and the size increased.

As is clear from Tables 2 and 3 and FIGS. 6 to 10, carbon microparticles (acetylene black) made hydrophilic by acid treatment with a mixed acid of sulfuric acid and nitric acid and having a small thickness and an appropriate size. It was found that a composite particle material having a large specific surface area and a small interdispersion degree (excellent dispersion degree) can be obtained by using the MXene exfoliate as a composite particle material. Furthermore, it was found that interdispersion degree and specific surface area were changed by changing the amount of carbon particles added.

In the process of uniformly mixing MXene and carbon particles, Method A, which intercalates chlorine ions, has a smaller average pore diameter and pore volume, and a larger specific surface area than Method B, which does not. rice field. Furthermore, in the XRD profile, it was found that the interlayer distance of the (002) plane of MXene was larger in the A method than in the B method (shown in Table 5). In addition, FIG. 12 shows a reference diagram regarding the measurement of the interlayer distance. MXene has a crystal structure obtained by removing the A phase from the MAX phase shown in FIG.

If the interlayer distance of the (002) plane of MXene minus 0.945 nm, which is the interlayer distance of the (002) plane of the MAX phase, is defined as the interlayer distance of the gap, the interlayer distance of the gap becomes larger. This suggests that larger ions can be inserted and detached.

When the amount of fine carbon particles was 3% by mass or more, the specific surface area increased, and when the amount was 10% by mass or less, the interdispersion degree could be improved. Therefore, it was found that the ratio of carbon microparticles is preferably 3 to 10% by mass based on the mass of MXene and carbon microparticles. In this case, the mutual dispersion degree is 1.50 when the carbon fine particles are 3% by mass and 7.00 when the carbon fine particles are 10% by mass, and the mutual dispersion degree is 1.50 or more and 7.00 or less. was found to be preferable.

It was found that sufficient battery characteristics were exhibited when the specific surface area was 75 m ² /g or more. In the examples, the composite particle material with a specific surface area of about 110 m ² /g showed the highest specific surface area.

Two methods (Method A and Method B) are used to produce a composite particle material of Ti ₃ Al _0.02 C ₂ MXene and conductive carbon black having a specific surface area of 75 m ² /g or more and an excellent interdispersion degree. compare. When a composite particle material of Ti ₃ Al _0.02 C ₂ MXene and carbon black is produced by method A, an average pore diameter of 7.0 to 15.0 nm and an average pore volume of 0.10 to 0.30 mL/g are obtained. When a composite particle material of Ti ₃ Al _0.02 C ₂ MXene and conductive carbon black is produced by method B, the average pore diameter is 15.0 to 20.0 nm and the average pore volume is 0.30 to 0.50 mL. /g, and it was found that the average pore diameter and average pore volume of the A method are smaller than those of the B method.

_{The zeta} potentials of _{Ti3Al0.02C2MXene} and _{Ti3Al0.02 ( C0.97N0.03} ) _2MXene at pH 7.0 in water are negative _, and their absolute values are 28.9 and 29.3, respectively. _{Ti3Al0.02 ( C0.95N0.05} ) _2MXene , _{Ti3Al0.02 ( C0.90N0.10} ) _{2MXene , Ti3Al0.02 ( C0.85N0.15 ) 2MXene , Ti3Al0.02 ( C0.75N0.25 ) 2} The absolute values of the zeta potential of MXene in water at pH 7.0 are 31.5, 32.1, 32.4 and 33.1, respectively. The latter means less likely to agglomerate. It was found that acid-treated acetylene black has negative zeta potential at pH 7.0 in water and becomes hydrophilic due to the dissociation of COOH and CO groups. Therefore, by stirring the aqueous suspension of MXene and the aqueous suspension of acid-treated acetylene black, it becomes possible to uniformly mix them, and when an alkaline aqueous solution is added, aggregates can be obtained while maintaining a uniformly dispersed state. I found out.

When the surface electrical resistance of the uniformly mixed composite particle material and the conventional composite particle material was measured using pellets that were subjected to CIP treatment after uniaxial pressing, the surface electrical resistance of the uniformly mixed composite particle material was small. was found (Table 4). When used as a negative electrode active material for a secondary battery, it is possible to effectively transfer electrons to the current collector.

By exfoliating the MXene nanosheets to the monolayer level and reducing the size to an appropriate size, a composite particle material with hydrophilized acetylene black is formed to increase the specific surface area and uniformly disperse acetylene black. By arranging them, the present inventors have produced a composite particle material that is excellent in ion diffusibility and capable of smoothly transferring electrons to a current collector, and which is ideally suited as a negative electrode active material for a secondary battery (storage battery).

Claims (11)

1. 90 to 97 parts by mass of sheet-like Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) MXene, and 3 to 10 parts by mass and a minute body of
   A composite particle material having a specific surface area of 75 m ² /g or more.
2. The composite particle material according to claim 1, wherein the microscopic bodies are carbon microscopic bodies.
3. In Raman spectroscopic analysis using a laser with a wavelength of 532 nm, the interdispersion index, which is the standard deviation of the ratio (B/A) of the peak height A at 400 cm ^-1 and the peak height B at 1332 cm ^-1 , is 1.50 to 7.0. 00. The composite particulate material of claim 1 .
4. The composite particle material according to any one of claims 1 to 3, which has an average pore diameter of 7.0 to 20.0 nm and a pore volume of 0.10 to 0.50 mL/g.
5. The Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) MXene has an average thickness of 1.0 to 3.5 nm, The average size of the sheet in the spreading direction is 0.5 to 1.0 μm,
   The composite particle material according to any one of claims 1 to 4, wherein the fine particles have a primary particle diameter of 30 to 50 nm.
6. In the crystal structure of the Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) MXene, the interlayer distance of the (002) plane is 1.0. 6. The composite particle material according to any one of claims 1 to 5, wherein the particle width is 400 nm to 1.700 nm and the half width is 0.9 degrees to 1.50 degrees.
7. 7. The composite particle material according to any one of claims 1 to 6, wherein the following surface electrical resistance is from 1.0 Ω/square to 100.0 Ω/square.
   (Surface electrical resistance)
   After the composite particle material was treated in vacuum at 100°C for 5 hours, it was uniaxially pressed with a φ10 mm mold at a pressure of 0.5 kg/cm ² and then subjected to CIP treatment at a pressure of 1.0 ton/cm ² . The electrical resistance of the surface measured by the four-probe method using a copper wire of φ0.1 mm is defined as the surface electrical resistance.
8. The fine particles are Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is 0.02 Super) MXene and the composite particulate material according to any one of claims 1 to 7, wherein the zeta potential is from -20.0 mV to -25.0 mV.
   The zeta potential is measured in water at pH 7.0.
9. A negative electrode comprising the composite particle material according to any one of claims 1 to 8 as a negative electrode active material.
10. _a stripping step of stripping _Ti3Ala (C( _{1.0 -x )} Nx) ₂ (0≤x≤0.03, a is greater than 0.02) MXene to form a stripped product;
    an acid treatment step of treating raw carbon microparticles in a mixed acid aqueous solution of sulfuric acid and nitric acid at 70° C. or higher for 10 minutes or longer to obtain carbon microparticles;
    a mixing step of obtaining a mixture in which the exfoliated matter and the carbon microparticles are dispersed in a second dispersion medium at a mass ratio of 90:10 to 97:3 and the exfoliated matter has a concentration of 11.5 to 17.0 mg/mL; ,
    adding an aqueous solution of lithium chloride with a shaker at 100 rpm to 300 rpm for intercalation;
    The liquid of the mixture is made alkaline and aggregated to form the Ti ₃ Al _a (C( _{1.0 -x} )N _x ) ₂ (0≦x≦0.03, a is greater than 0.02) MXene and the an agglomeration step of obtaining a composite particle material of fine carbon particles;
    A method for producing a composite particulate material having
11. 11. The method for producing a composite particulate material according to claim 10, wherein the peeling step is a step in which 99% or more of the MXene on a mass basis becomes the peeled material.

Images