JP2021187733A - Coated composite particle - Google Patents

Abstract

To provide coated composite particles having low electrical resistance at a low density (0.8 g/cm3).SOLUTION: The present invention pertains to coated composite particle (C) in which a surface of a composite material (A) containing a carbon material and silicon is coated with an organic compound layer (B) containing polyaniline, where the nitrogen atom content and the phosphorus atom content of the organic compound layer (B) relative to the coated composite particle (C) are 0.2-0.7 mass% and 0.08-0.6 mass%, respectively.SELECTED DRAWING: Figure 1

Description

The present invention relates to coated composite particles.

Secondary batteries used in IT devices such as smartphones and tablet PCs, vacuum cleaners, electric tools, electric bicycles, drones, and automobiles require negative electrode active materials having high capacity and high output. As a negative electrode active material, silicon (theoretical specific capacity: 4200 mAh / g) having a higher theoretical specific capacity than graphite (theoretical specific capacity: 372 mAh / g) currently used is attracting attention.

However, the volume of silicon (Si) expands and contracts up to about 3 to 4 times with the electrochemical insertion and desorption of lithium. It is known that a lithium ion secondary battery using silicon has extremely low cycle characteristics because the silicon particles self-destruct or peel off from the electrode due to this. For this reason, it is currently being actively studied to use silicon as a whole with a structure in which the degree of expansion and contraction is reduced, instead of simply replacing it with graphite. Among them, many attempts have been made to combine with carbonaceous materials.

As a negative electrode material having a high capacity and a long life, for example, Patent Document 1 is obtained by a method of producing silicon in the pores of porous carbon by contacting porous carbon particles with silane gas at a high temperature. Further, a silicon-carbon composite material (Si-C composite material) is disclosed. In Patent Document 1, the Si—C composite material is further coated with a carbonaceous layer by a chemical vapor deposition (CVD) method, or a silicon-carbon composite material (hereinafter, referred to as a Si—C composite material). There is.) Discloses a composite material mixed with phytic acid.
Further, Patent Document 2 discloses a composite material in which silicon fine particles are surrounded by a network formed of polyaniline and phytic acid.

Special Table 2018-534720 Publication No. International Publication No. 2014/026112

When the material in which the carbonaceous layer is coated on the Si—C composite material disclosed in Patent Document 1 is used as the negative electrode active material, the carbon coverage of the Si—C composite material is low in the low temperature treatment and the surface silicon (Si) is exposed. Was not suppressed, and the Si—C composite material was oxidized, resulting in a decrease in the initial Coulomb efficiency. Further, in the high temperature treatment, the specific capacity of the lithium ion secondary battery decreased due to the formation of silicon carbide (SiC).
Further, Patent Document 2 discloses a composite material in which silicon fine particles are surrounded by a network in which polyaniline and phytic acid are bonded. When this composite material is used as an active material for a lithium-ion secondary battery, there is a problem that the distance between the silicon fine particles and the network fluctuates due to the volume fluctuation during expansion and / or contraction of the silicon fine particles, and the electrical resistance increases. there were. In addition, since particulate silicon is used, it is not sufficient to surround the silicon fine particles with a network in which polyaniline and phytic acid are bound in order to suppress the structural collapse of the silicon fine particles due to expansion and contraction due to charge and discharge.
The present invention provides coated composite particles capable of lowering electrical resistance at ^{low densities (0.8 g / cm 3} ) in order to obtain lithium ion secondary batteries with high discharge capacity, initial Coulomb efficiency, and cycle characteristics. The task is to do.

The present invention has the following configuration.
[1] The surface of the composite material (A) containing a carbon material and silicon is a coated composite particle (C) coated with an organic compound layer (B) containing polyaniline.
The coated composite having a nitrogen atom content of 0.2 to 0.7% by mass and a phosphorus atom content of 0.08 to 0.6% by mass in the organic compound layer (B) with respect to the coated composite particles (C). particle.
[2] The above-mentioned [1], wherein the nitrogen atom content in the coated composite particle (C) is 0.4 to 3.6% by mass, and the phosphorus atom content is 0.08 to 9.6% by mass. Coated composite particles.
[3] The above-mentioned [2], wherein the nitrogen atom content in the coated composite particle (C) is 0.5 to 1.2% by mass, and the phosphorus atom content is 0.08 to 0.6% by mass. Coated composite particles.
[4] The coated composite particle according to any one of the above [1] to [3], wherein the phosphorus atom of the coated composite particle (C) is derived from a compound having a plurality of phosphoric acid groups.
[5] The coated composite particle according to the above [1] to [4], wherein the phosphorus atom of the coated composite particle (C) is derived from phytic acid.
[6] The coated composite particle according to any one of the above [1] to [5], wherein the nitrogen atom of the organic compound layer (B) is derived from polyaniline.
[7] The coated composite particle according to the above [6], wherein the polyaniline and phytic acid are bonded in the organic compound layer (B).
[8] The organic compound layer (B), in the Raman ^{spectroscopy, 1475~1525cm -1, 1140~1190cm -1,} also has a peak in any of the wavenumber range 785～835Cm ^-1, wherein [1] The coated composite particle according to any one of [7].
[9] The organic compound layer (B), in the Raman ^{spectroscopy, 1592 ± 5cm -1, 1494 ±} 5cm -1, a peak to each wave number range of 1165 ± ^{5 cm -1} and 806 ± ^{5 cm -1} , The coated composite particle according to any one of the above [1] to [7].

According to the coated composite particles of the present invention, a thin coating layer of an organic compound containing polyaniline is formed on the surface of a composite material containing a carbon material and silicon, so that ^{electricity at a low density (0.8 g / cm 3} ) is obtained. It is possible to provide a negative electrode active material of a lithium ion secondary battery having a low resistance.

It is a figure which shows the Raman spectrum of the coated composite particle obtained in Example 4. FIG. It is a figure which shows the Raman spectrum of the coated composite particle obtained in the comparative example 1. FIG. It is a figure which shows the observation image of the coating composite particle obtained in Example 1 with a scanning electron microscope. It is a figure which shows the observation image of the coating composite particle obtained in Example 4 with a scanning electron microscope. It is a figure which shows the observation image of the coating composite particle obtained in the comparative example 5 with a scanning electron microscope. It is a figure which shows the observation image of the coating composite particle obtained in the comparative example 7 with a scanning electron microscope. It is a figure which shows the Raman spectrum of the coated composite particle obtained in the comparative example 5-7.

Hereinafter, embodiments of the present invention will be described.
In the following description, "peak intensity" represents the height of the peak.

[1] Coated composite particles (C)
The coated composite particle (C) according to the embodiment of the present invention is a coated composite particle (C) in which the surface of the composite material (A) containing a carbon material and silicon is coated with an organic compound layer (B) containing polyaniline. The nitrogen atom content measured by the oxygen / nitrogen elemental analysis method is 0.4 to 3.6% by mass, preferably 0.5 to 1.2% by mass, and high frequency of the coated composite particle (C). The phosphorus atom content measured by inductively coupled plasma emission spectroscopic analysis (ICP-AES method) is 0.08 to 9.6% by mass, preferably 0.08 to 0.6% by mass of the coated composite particle (C). Is. Furthermore, the 50% particle size in cumulative particle size distribution on the volume basis as determined coated complex particles (C) by a laser diffraction method (D _V50) is coated complex particles is 2 to 30 m.

Although silicon has a high theoretical capacity, it expands and contracts greatly with charge and discharge, and when used as an electrode active material, the density of the electrode decreases with the charge and discharge cycle, and the conductivity decreases. The coated composite particles of the present invention use a composite material (A) containing silicon and a carbon material instead of silicon, and the composite material is further coated with a conductive organic compound layer (B) containing polyaniline. Therefore, it is possible to reduce the electric resistance at a low powder density. Therefore, even when the electrode density decreases, it is expected to suppress the decrease in conductivity and suppress the decrease in performance.

In one embodiment, a compound having a plurality of phosphate groups is ionically bonded to the amino group of polyaniline contained in the organic compound layer (B), and the polyaniline forms a crosslinked structure. Therefore, a composite material containing a carbon material and silicon. A three-dimensional network structure of polyaniline can be constructed on the surface of (A). Here, the crosslinked structure formed by polyaniline refers to a state in which a network structure is formed by ionic bonding between an amino group of polyaniline and a compound having a plurality of phosphate groups. This crosslinked structure is also referred to as a polyaniline network structure.

Further, when the crosslinked structure as described above is formed, the organic compound layer (B) formed on the surface of the composite material (A) containing the carbon material and silicon has fine irregularities on the surface, so that the powder is low. It is considered that the conductivity is exhibited even at the body density (hereinafter, also referred to as low density).
The nitrogen atom content of the coated composite particle (C) is preferably 0.5 to 1.2% by mass, more preferably 0.6 to 1.0% by mass, and further preferably 0.8 to 1.0% by mass. Is. The phosphorus atom content is preferably 0.08 to 0.6% by mass, more preferably 0.2 to 0.6% by mass, and even more preferably 0.3 to 0.6% by mass.
Examples of the compound having a plurality of phosphoric acid groups ionically bonded to the amino group of polyaniline include phosphoric acid groups such as polyphosphoric acid, phytic acid, 2-methacryloxyethyl acid phosphate or 2-acryloyloxyethyl acid phosphate. Examples thereof include (co) polymers of (meth) acrylates having and salts thereof. Phytic acid is preferred. Having many phosphate groups in one molecule can ionically bond with polyaniline and preferably form a polyaniline network structure on the surface of the composite material (A) containing the carbon material and silicon.
As the nitrogen-containing compound of the coated composite particle (C), a compound having a functional group derived from an amino group ionically bonded to a phosphoric acid machine is preferable, and examples thereof include polyaniline in an organic compound layer. It may contain an aniline monomer. The organic compound layer (B) preferably has an ionic bond between polyaniline and phytic acid.

Coated complex particles according to an embodiment of the present invention (C) is preferably a BET specific surface area is less than 40.0m ² / g, more preferably not more than ^{30.0m 2 / g, 20.0m 2 /} g The following is more preferable. When the BET specific surface area is 40.0 m ^{2 /} g or less, the decomposition reaction of the electrolytic solution, which is a side reaction, is unlikely to occur, and the initial Coulomb efficiency can be increased. The BET specific surface area is ^{preferably 0.50 m 2} / g or more. When the BET specific surface area is 0.50 m ² / g or more, lithium ions can be easily inserted and removed, and the cycle characteristics can be improved. The BET specific surface area can be measured by the method described in Examples.

Coated complex particles according to an embodiment of the present invention (C) is the 50% particle diameter _{D V50} in cumulative particle size distribution on the volume basis is 2 to 30 m. _DV50 can be measured by laser diffraction. When the _{DV50 of the} composite particles is 2 μm or more, the powder of the coated composite particles (C) has excellent handleability, it is easy to prepare a slurry having a viscosity and density suitable for coating, and when an electrode is formed, it is easy to prepare. It is easy to increase the density of electrodes.
Furthermore, if D _V50 is a 30μm following coated complex particles (C), one single addition diffusion length of lithium excellent in rate characteristics of the lithium ion battery to become shorter in the particles, applied to the current collector as a slurry No streaks or abnormal irregularities occur when doing so. From this point of view, the _DV50 is more preferably 25 μm or less, and even more preferably 20 μm or less.

In the coated composite particle according to the embodiment of the present invention, in the XRD pattern by powder XRD measurement using Cu—Kα ray, the half width of the peak of the 111th surface of Si was 3.00 deg. The above is preferable, and 4.00 deg. The above is more preferable, and 5.00 deg. The above is more preferable. 3.00 deg. As described above, the size of the crystallites is small and the amorphousness is high, which leads to suppression of cracking of silicon particles due to charging and discharging, and can improve cycle characteristics.

The coated composite particle according to one embodiment of the present invention has (peak intensity of SiC111 surface) / (peak intensity of Si111 surface) of 0.01 or less in an XRD pattern measured by powder XRD using Cu—Kα ray. Is preferable. As a result, SiC (silicon carbide) is not contained in the coated composite particles, or the content of SiC is extremely low, so that the utilization rate of silicon as a battery active material is improved and the initial discharge capacity is increased. Can be high. The (peak intensity of the SiC111 surface) / (peak intensity of the Si111 surface) is also referred to as _{I SiC111} / I _Si111. It is more preferable that the lower limit of I _SiC / I _Si111 is 0, that is, no peak intensity of SiC is observed. The peak intensity of SiC means the peak height that appears in the vicinity of 35 ° at 2θ derived from SiC. The peak intensity of Si means the peak height that appears in the vicinity of 28 ° at 2θ derived from Si.

The content of silicon (Si atom) in the composite material (A) in the coated composite particle (C) according to one embodiment of the present invention is preferably 20% by mass or more, more preferably 30% by mass or more. When the silicon content is 20% by mass or more, it is theoretically possible to obtain a discharge capacity of about 1000 mAh / g or more, which greatly exceeds the theoretical discharge capacity of graphite. The silicon content is preferably 70% by mass or less, more preferably 65% by mass or less, and even more preferably 60% by mass or less. When the silicon content of the coated composite particles is 70% by mass or less, the porous carbon as a carrier can absorb the volume change due to the expansion and contraction of the coated composite particles.

The silicon content in the coated composite particles can be determined by the fundamental parameter method (FP method) in the fluorescent X-ray analyzer.

[2] Composite material (A)
The composite material (A) in one embodiment of the present invention is not limited as long as it contains a carbon material and silicon. As the carbon material, amorphous carbon materials such as soft carbon and hard carbon, carbon fibers, vapor phase carbon fibers, multi-wall carbon nanotubes, single-wall carbon nanotubes, nanowires, graphite materials, and activated carbon can be used. Amorphous carbon materials and graphite materials are preferable, and amorphous carbon materials are more preferable because they have high electron conductivity, excellent cycle characteristics, and high electrode density.

Further, the carbon material is preferably a porous carbon material. The structure of the composite material (A) containing the porous carbon material and silicon is not limited, but the composite material (A) in which the pores in the porous carbon material are filled with silicon is preferable. Examples of porous carbon materials include activated carbon, carbon obtained by thermally decomposing resins and organic substances, molecular sieving carbon, activated carbon fiber, agglomerates of vapor-grown carbon fibers, agglomerates of carbon nanotubes, and inorganic materials. Template carbon can be mentioned. The porous carbon material can be produced by a known production method, for example, by the same production method as activated carbon or by performing an appropriate heat treatment on the polymer. The method of including silicon is not limited, but for example, by chemical vapor deposition (CVD), a porous carbon material (for example, porous amorphous carbon) is added to the silane gas at a high temperature in the presence of a silicon-containing gas, preferably silane. It is obtained by exposing the material) to form silicon in the pores of the porous carbon material. At this time, silicon may also be deposited on the surface of the porous carbon material.
The porous carbon material preferably has a BET specific surface area of 200 m ² / g or more.

To investigate the pore distribution of porous carbon, for example, the adsorption isotherm by the gas adsorption method is analyzed by a known method. The probe gas is not particularly limited, but nitrogen gas, carbon dioxide, and argon are usually used.

[3] Organic compound layer (B)
The organic compound layer (B) is a layer that covers the surface of the composite material (A). The organic compound layer (B) may cover the entire surface of the composite material (A), or may cover a part of the surface. The coverage of the surface of the composite material (A) with the organic compound layer (B) is preferably high. The organic compound layer is obtained by polymerizing an aniline monomer on the surface of the composite material (A) to produce polyaniline. Details will be described later. The method for forming the organic compound layer (B) is not particularly limited, but it is preferable to polymerize the aniline monomer in the presence of the phosphoric acid group-containing compound in order to improve the conductivity with the composite material (A).

In the organic compound layer (B), it is preferable that the phosphoric acid group-containing compound and polyaniline are ionically bonded. By ionic bonding, polyaniline can form a cross-linked structure with phosphate groups and form a network. With this crosslinked structure, the conductivity can be improved and the electric resistance at the pressure ^{density (0.8 g / cm 3) can be lowered.} The degree of consolidation is a 0.8 g / cm ³ is that the density when the apparent density of the coated complex particles (C) was compressed so that 0.8 g / cm ³ (of compaction). In this crosslinked structure, for example, when aniline is polymerized in the presence of phytic acid having a phosphoric acid group, a gel-like substance is formed, and the coated composite particles (C) coated with the organic compound layer (B) are scanned. When observed with an electron microscope (SEM), the presence of the coated composite particles (C) can be confirmed by the uneven shape of the surface. This unevenness can also be measured by AFM, which will be described later. Further, by performing a Raman spectrum of the coated composite particle (C) described later, the existence of a structure formed by binding polyaniline and phytic acid can be confirmed.

The surface roughness (Sq: root mean square height) of the surface of the coated composite particle (C) can be measured by an atomic force microscope (AFM) described later. This root mean square is the standard deviation of the height distribution. The surface roughness (Sq: root mean square height) is preferably 10 nm or more. If it is 10 nm or more, it is considered that polyaniline and phytic acid can form a network and exhibit good conductivity, and can coat the composite material (A) containing a carbon material and silicon.
Coated complex particles of an embodiment (C) is a Raman spectrum by Raman ^{spectroscopy, 1475~1525cm -1, 1140~1190cm -1,} it has a peak in any of the wavenumber range of 785～835Cm ^-1 If so, the electric resistance at the pressure density (0.8 g / cm3) can be more preferably lowered.
Polyaniline is known to have four structures: oxidation, reduction, protonation, and deprotonation, and only the protonated emeraldine structure in it exhibits conductivity. The formation of the emeraldine structure in the polyaniline of the organic compound layer (B) is 1592 ± 5 cm ^-1 (C = C) and 1494 ± 5 cm ^{− showing quinoid ring expansion and contraction vibration in the Raman spectrum measured by Raman spectroscopy. 1} (C = N), Quinoid ring surface in-plane variable angle vibration 1165 ± 5 cm ^-1 (CH), benzene ring surface out-of-angle variable angle vibration 806 ± 5 cm ^-1, etc. Confirm by having a peak in the wavenumber range. Can be done. As a result of measuring the Raman spectrum of the coated composite particles (C) by Raman spectroscopy, if a peak derived from the emeraldine structure of the above polyaniline is observed, the organic compound layer (B) is observed on the surface of the coated composite particles (C). Can be considered to be formed.

The thickness of the organic compound layer (B) is preferably 0.1 nm or more. Further, from the viewpoint of having a certain level of conductivity, chemical stability, and mechanical strength, the thickness of the organic compound layer (B) is preferably 1 nm or more, more preferably 2 nm or more. The thickness of the organic compound layer (B) is preferably 50 nm or less. When the thickness of the organic compound layer (B) is 50 nm or less, the formation of the excessive organic compound layer (B) is suppressed, and the initial coulomb efficiency and the discharge capacity retention rate can be improved. From the same viewpoint, 30 nm or less is more preferable.

The thickness of the organic compound layer (B) can be measured by observing the cross section of the coated composite particle (C) by a known method such as observation with a transmission electron microscope (TEM). The thickness of the organic compound layer (B) refers to an average value. For example, the average thickness is calculated from the TEM observation image of a typical portion, and the average value of the thickness is obtained in the same manner as in 10 places, and the obtained 10 points are obtained. The average value can be further calculated from the average thickness of.

[4] Method for Producing Coated Composite Particles (C) The coated composite particles (C) in one embodiment of the present invention can be obtained by forming polyaniline on the surface of the composite material (A) in the presence of phytic acid. Can be done. An example is given below.

[Preparation of coated composite particles]
Aniline monomer and a compound having a phosphoric acid group are added to a container containing the composite material (A), and the mixture is stirred. Further, it is preferable to add water to make an aqueous solution because stirring becomes easy. At this time, it is preferable to cool the temperature to 5 ° C. or lower. Then, ammonium persulfate (APS) is added little by little with stirring. After the addition is completed, it is preferable to continue stirring for several hours to 10 hours for the reaction. Then, using a membrane filter, this solution (an aqueous solution containing an unreacted substance) is filtered, and the residue is recovered. This residue is washed with pure water and then vacuum dried. The product obtained after drying is the coated composite particle (C). At this time, the aniline monomer is polymerized to form polyaniline, and a network structure in which a phosphoric acid group is ionically bonded to this polyaniline is formed.

Hereinafter, embodiments of the present invention will be specifically described. It should be noted that these are merely examples for explanation and do not limit the present invention.
The evaluation methods of the composite carbon materials of Examples and Comparative Examples and the raw materials used in each example are as follows.

[1] Evaluation of coated composite particles [Measurement of 50% particle size (D _V50 ) and 10% particle size (D _V10 )]
Add 1 cup of powder of coated composite particles (C) and 2 drops of nonionic surfactant (SIRAYA palm fruit detergent high power) stock solution 32% 100 times diluted solution to 15 mL of water 3 Ultrasonic dispersion was performed for a minute. The dispersion Seishin Enterprise Co., Ltd. laser diffraction particle size distribution measuring apparatus was placed in (LMS-2000e), measuring the volume-reduced cumulative particle size distribution, the 50% particle size _{(D V50),} 10% particle size _{(D V10)} It was determined.

[Nitrogen content measurement]
1. 1. Content in Coated Composite Particles (C) The nitrogen atom content of the coated composite particles (C) obtained in Examples and Comparative Examples was measured under the following conditions.
About 10 mg of the coated composite particles were placed in a nickel capsule and weighed, and measured by an oxygen-nitrogen simultaneous analyzer (inert gas melting-heat conductivity method).
Oxygen / nitrogen / hydrogen analyzer (oxygen / nitrogen simultaneous analyzer): TC-600 (manufactured by LECO)
Carrier gas: Argon Output: 5000W
Graphite crucible: High temperature type 2. Content in the organic compound layer (B) The coated composite particles (C) obtained in Examples and Comparative Examples are measured by the method 1 described above. The composite material (A) was also measured by the same method as in 1, and the value obtained by subtracting the result of the composite material (A) from the result of the coated composite particle (C) was taken as the value of the organic compound layer (B).

[Phosphorus content measurement]
1. 1. Content in Coated Composite Particles (C) The phosphorus atom content of the coated composite particles obtained in Examples and Comparative Examples was measured under the following conditions.
Approximately 0.03 g of the coated composite particles were weighed in a PTFE beaker and completely decomposed with a mixed solution of nitric acid sulfate and hydrofluoric acid. After allowing to cool, the volume was set to 50 ml, phosphorus was quantified by inductively coupled plasma emission spectroscopy (ICP-AES method), and converted to a sample concentration. The analysis was performed with n = 2 and the average value was used.
Device: Agilent 5110 (Agilent technology)
2. 2. Content in the organic compound layer (B) The coated composite particles (C) obtained in Examples and Comparative Examples are measured by the method 1 described above. The composite material (A) was also measured by the same method as in 1, and the value obtained by subtracting the result of the composite material (A) from the result of the coated composite particle (C) was taken as the value of the organic compound layer (B).

[Measurement of silicon content]
The measurement was performed under the following conditions.
X-ray fluorescence device: NEX CG manufactured by Rigaku
Tube voltage: 50 kV
Tube current: 1.00mA
Sample cup: Φ32 12mL CH1530
Sample weight: 3g
Sample height: 11 mm
The powder of the coated composite particle (C) was introduced into the sample cup, and the silicon content was measured by the FP method.
The Si concentration (mass%) was obtained by multiplying the silicon content by 100.

[Surface SEM observation]
Under the following conditions, the surfaces of the coated composite particles obtained in Examples and Comparative Examples were observed by SEM.
Scanning electron microscope: Hitachi High-Technologies Corporation SU8222
Acceleration voltage: 1kV
Magnification: 100,000 times

[Raman spectroscopy measurement]
Raman spectroscopy measurement of the coated composite particles (C) obtained in Examples and Comparative Examples was performed under the following conditions.
Microscopic Raman spectroscopic measuring device: HORIBA, Ltd. LabRAM HR Evolution
Excitation wavelength: 532 nm
Exposure time: 5 seconds Total number of times: 2 Diffraction gratings: 300 lines / mm (600 nm)
Measurement range: length 80 μm x width 100 μm
Number of points: 100 points were evaluated with a vertical feed of 17.8 μm and a horizontal feed of 22.2 μm, and the micro Raman spectrum of the coated composite particle (C) was measured. This result is the same as measuring the organic compound layer (B) present on the surface of the coated composite particle (C).
1475~1525cm ^-1, 1140~1190cm ^-1, organic compound layer that has a peak in any of 785～835Cm ^-1 (B), the the compound having the polyaniline and phosphate groups are the ionic bond It was used as an index. ^{Furthermore, 1592 ± 5cm -1, 1494 ±} 5cm -1, 1165 ± 5cm -1, if confirmed to have a peak in the range of 806 ± ^{5 cm -1,} to confirm the presence of emeraldine structure of polyaniline exhibits conductivity be able to. The Raman spectra of Example 4, Comparative Example 1, and Comparative Examples 5 to 7 are shown in FIGS. 1, 2, and 7, respectively.

[Roughness (Sq) measurement]
Sample setting A water dispersion (about 5 mg / mL) in which the obtained coated composite particles are dispersed is dropped onto the Si substrate, and then vacuum dried (normal temperature) to immobilize the coated composite particles to prepare a sample substrate. did. This sample substrate was adhered with carbon tape on a sample disk of an atomic force microscope (AFM) and observed.
AFM observation device: Dimension XR Nanomechanics / Bruker probe: PPP-NCHR / NanoWorld probe radius of curvature: 7 mm / spring constant: 42 N / m
Measurement conditions: Tapping mode Scan range: 2 x 2 μm (data density: 512 x 512)
Scan speed: 1.0Hz
Measurement frequency: Around 300 kHz Amplitude Setpoint: Approximately 25 nm Surface roughness (Sq: root mean square height) Measurement Data-corrected (Plane fit) shape image, field view (area: 1) that does not include large convex parts (surface fine powder) .00 μm 2) was selected and the surface roughness was measured.
Details of data correction (Plane fit): The analysis software automatically applied the Plane fit for fitting (mode: tilt correction in XY, Order: 1st, Z-axis offset and image tilt are removed). It was performed with n = 10, and the average value was calculated.

[Measurement of consolidation resistivity (low powder density)]
The measurement was performed under the following conditions.
1. 1. A predetermined weight of the coated composite particles obtained in Examples and Comparative Examples is added to a powder resistance cell having a compression surface of 5 mm × 10 mm.
2. 2. A compression device that measures resistance while compressing with a device that combines a compression device and an electrical resistance measuring device: Tencilon universal material tester RTG-1310 manufactured by A & D.
Current generator: DC Voltage Current Source 6146 made by ADCMT
Voltmeter: ADCMT Digital Multimeter 7532E
Compression condition: 5 mm / min
The stress and the moving distance (compression height) of the compression device are measured every 0.5 seconds.
Stop condition: 1.25kN
Electrical measurement conditions: Apply a constant current (1 mA) and measure the voltage (xV).
Measure the voltage every 0.5 seconds.
Distance between current application electrodes: 10 mm
Distance between voltage measurement electrodes: 6.5 mm
The analysis method is as follows.
1. 1. Pressure (N / m ² ): Calculate the pressure at each measurement (0.5 seconds) from the stress and compression area. Density (g / cm ³ ): Calculate the volume from the sample amount, compression height and compression area at each measurement.
3. 3. Volume resistivity (Ω · cm): The volume is calculated from the resistance (xV / mA) at each measurement, the compression height and the compression area, and the resistivity per unit volume is calculated.
In one embodiment, the volume resistivity with respect to the density was plotted according to the above, and the volume resistivity (Ω · cm) ^{at a density of 0.8 g / cm 3 was calculated as the consolidation ratio resistance.}

[2] Raw Materials The following shows the preparation methods, sources, and physical property values of the coated composite particles (C) and its raw materials (composite material (A), organic compound layer (B)).

[Composite material (A)]
BET specific surface area of 1700 m ² / g, a particle size _{D V50} is against commercial activated carbon 9.2 .mu.m, set temperature 450 ° C. in a tube furnace having a silane gas flow of 1.3 vol% mixed with nitrogen gas, pressure 760 torr, The treatment was carried out at a flow rate of 100 sccm for 8 hours to precipitate silicon on the surface and inside of the porous carbon to obtain a composite material (A). The composite material (A) _{is, D V50} is 9.2 .mu.m, BET specific surface area of 3.2 m ² / g, a silicon content of 48 mass%.

[Organic compound layer (B)]
Aniline: Tokyo Chemical Industry Co., Ltd., CasNo. 62-53-3, component> 98.0%, SG1.02
Phytic acid: Tokyo Chemical Industry Co., Ltd., CasNo. 83-86-3, ca. 50% in water ca.1.1M
APS (Ammonium Persulfate): Tokyo Chemical Industry Co., Ltd., CasNo. 7727-54-0, component> 99.0%
Hydrochloric acid: Fujifilm Wako Pure Chemical Industries, Ltd., CasNo. 7647-01-0, special grade

[Coated composite particles (C)]
The weighed composite material (A) is charged into a 20 cc glass container so as to have 86 parts by mass. Place the glass container in an ice bath with a constant temperature of 5 degrees or less. The mass parts of aniline and phytic acid shown in Table 1 are put into a glass container, and stirring is started with a stirrer set at 60 rpm. After 5 minutes, the mass parts of APS shown in Table 1 are charged into a glass container at 3 ml / min and stirred with a stirrer set at 80 rpm. After 5 hours, stop stirring and remove the glass container from the ice bath. The solution in the glass container is filtered using a PTFE membrane filter having a maximum pore size of 0.1 μm. After filtration, wash the recovered material on the membrane filter with about 500 ml of pure water. The residue recovered after washing is allowed to stand for 8 hours in a vacuum oven at 60 ° C. reduced to −760 mmHg, and dried.
The coated composite particles (C) were recovered after a lapse of a predetermined time, and the above-mentioned evaluation was carried out using the coated composite particles (C).

[Example 1]
A predetermined amount was prepared so as to be 86 parts by mass of the composite material (A), 4 parts by mass of aniline, 6 parts by mass of phytic acid and 3 parts by mass of APS, and the coated composite particles (C) were prepared by the above-mentioned method. Table 1 shows the results of acquiring the physical property values of the coated composite particles (C) in the evaluation items and methods described above.
In Example 1, it was confirmed by a surface SEM image (FIG. 3), Raman spectroscopy, and AFM that the organic compound layer (B) having an uneven shape of several tens to several hundreds of nm was formed.

In the obtained coated composite particles (C), the organic compound layer (B) is formed on about half of the entire surface of the composite material (A), and the surface of the organic compound layer (B) has an uneven shape almost entirely. I was doing it. The 1475～1525Cm ^-1 in the Raman spectrum, 1140~1190cm ^-1, has a peak in any of 785～835Cm ^-1 was confirmed. In addition, peaks were observed in the ranges of 1592 ± 5 cm ^-1 , 1494 ± 5 cm ^-1 , 1165 ± 5 cm ^-1 and 806 ± 5 cm ^-1 , confirming the formation of polyaniline and the formation of emeraldine structure by acid. The emeraldine structure is considered to be a network structure in which polyaniline and an acid (phytic acid) are ionic bonded. When the consolidation specific resistance was also compared with Comparative Examples 1 to 7 described later, it was confirmed that the resistance in the low density region was low and the result was superior (Table 1).

[Examples 2 to 5]
The coated composite particles (C) were produced in the same manner as in Example 1 except that the types and addition amounts of each material were as shown in Table 1, and the physical property values of the coated composite particles (C) were as in Example 1. Was obtained. The results are shown in Table 1. The surface SEM image of Example 4 is shown in FIG. It was confirmed that the organic compound layer (B) having an uneven shape of several tens to several hundreds of nm was formed in each of Examples 2 to 4. The Raman spectrum of Example 4 is shown in FIG. Raman spectra 1475~1525cm ^-1, 1140~1190cm ^-1, it was confirmed that a peak in any 785~835cm ^-1. In addition ^{Specifically, 1591cm -1, 1498cm -1,} a peak was observed at 1166cm ^-1 and 809cm ^-1 (Fig. 1), the formation of the emeraldine structure by forming an acid polyaniline was confirmed. The emeraldine structure is considered to be a network structure in which polyaniline and an acid (phytic acid) are ionic bonded. As for the consolidation specific resistance, as in Example 1, it was confirmed that the resistance in the low density region was low.
Note that the _{D V50} of Example 3 9.4 _{.mu.m, D V10} was confirmed to be a 5.7 .mu.m. On the other hand, International Publication No. 2014/026112 exemplifies that the diameters are 60 nm and 100 nm, and in another form, nano-order silicon particles having an average diameter of 500 to 1000 nm are surrounded by a network of polyaniline and phytic acid. It can be seen that the size is different from that of the coated composite particles of one embodiment.

[Comparative Example 1]
As an example in which neither polyaniline nor phytic acid is added and the organic compound layer (B) is not coated, Table 1 shows the results of obtaining the physical property values of the composite material (A) in the same manner as in Example 1. It was confirmed by the surface SEM image that the organic compound layer (B) was not formed. The Raman spectrum is shown in FIG. Raman spectra 1475~1525cm ^-1, 1140~1190cm ^-1, peak to any 785～835Cm ^-1 was observed. The consolidation specific resistance in the low density region was unmeasurable due to the high resistivity unlike Examples 1 to 5. In Examples 1 to 5, it was confirmed that the consolidation specific resistance in the low density region was reduced as compared with Comparative Example 1 by the formation of the organic compound layer (B).

[Comparative Example 2, Comparative Example 3]
The coated composite particles (C) were produced in the same manner as in Example 1 except that the types and addition amounts of each material were as shown in Table 1, and the physical property values of the coated composite particles (C) were as in Example 1. The results of obtaining the above are shown in Table 1. The presence of the organic compound layer (B) was confirmed from the shape of the unevenness on the surface of the coated composite material (C) and the Raman spectrum, but when the consolidation resistivity was compared with Examples 1 to 5, the consolidation ratio in the low density region was confirmed. The resistivity became high and could not be measured. From this result, it was confirmed that the organic compound layer (B) covering the composite material (A) was formed, but a sufficient effect of reducing the consolidation specific resistance could not be obtained. It is considered that the organic compound layer (B) is thin and the coverage (= the region where the organic compound layer (B) is formed in the total surface area of the coated composite particles (C)) is low.

[Comparative Example 4]
The coated composite particles (C) were produced in the same manner as in Example 1 except that the types and addition amounts of each material were as shown in Table 1, and the physical property values of the coated composite particles (C) were as in Example 1. The results of obtaining the above are shown in Table 1.
Similar to Example 5, the presence of the organic compound layer (B) was confirmed from the shape of the unevenness on the surface of the coated composite material (C) and the Raman spectrum, but the consolidation resistivity was higher than that of Examples 1 to 5. It became resistance and could not be measured. It is considered that the effect of reducing the consolidation specific resistance could not be obtained because the organic compound layer (B) covering the composite material (A) became too thick.

[Comparative Example 5]
The coated composite particles (C) were produced in the same manner as in Example 1 except that the types and addition amounts of each material were as shown in Table 1, and the physical property values of the coated composite particles (C) were as in Example 1. The results of obtaining the above are shown in Table 1. From the SEM image, the organic compound layer (B) was confirmed, but it was confirmed that the shape was different (there was almost no uneven shape) as compared with Examples 1 to 5 (FIG. 5). ^{Although polyaniline is considered to be formed, the peaks (1475-1525 cm -1} , 1140 to 1190 cm ^-1 , 785 to 835 cm ^-1 ) characteristic of the organic compound layer (B) of one embodiment are also observed from the Raman spectrum. The existence was not confirmed (Fig. 7).
When the consolidation specific resistance was also compared with Examples 1 to 5, the consolidation specific resistance in the low density region became high resistance and could not be measured as in Comparative Example 1.
Even if the organic compound layer (B) is formed on the composite material (A), it is considered that polyaniline does not have an emeraldine structure exhibiting conductivity because of the absence of acid, resulting in high consolidation resistivity in the low density region. It is thought that it became.

[Comparative Example 6]
The coated composite particles (C) were produced in the same manner as in Example 1 except that the types and addition amounts of each material were as shown in Table 1, and the physical property values of the coated composite particles (C) were as in Example 1. The results of obtaining the above are shown in Table 1. Although the organic compound layer (B) was confirmed from the SEM image, it was confirmed that the shape was similar to that of Comparative Example 5, and that the surface shape of the organic compound layer (B) was different from that of Examples 1 to 5. ^{The presence of peaks (1475-1525 cm -1} , 1140 to 1190 cm ^-1 , 785 to 835 cm ^-1 ) characteristic of the organic compound layer (B) was not confirmed from the Raman spectrum (FIG. 7).
When the consolidation specific resistance was also compared with Examples 1 to 5, the consolidation specific resistance in the low density region became high resistance and could not be measured as in Comparative Example 5.
Hydrochloric acid was used as the acid in Comparative Example 6, but it is considered that it was not possible to form a three-dimensional network structure with polyaniline because of the monofunctional group. In addition, since the amount of acid was small, it is considered that polyaniline does not have an emeraldine structure showing conductivity. From the above, when phytic acid having a plurality of acid functional groups in one molecule is not used as an acid, even if the organic compound layer (B) covers the composite material (A), the compaction ratio in the low density region It was confirmed that the resistance was higher than that of Examples 1 to 5.

[Comparative Example 7]
The coated composite particles (C) were produced in the same manner as in Example 1 except that the types and addition amounts of each material were as shown in Table 1, and the physical property values of the coated composite particles (C) were as in Example 1. The results of obtaining the above are shown in Table 1. From the SEM image (FIG. 6), the portion where the organic compound layer (B) having an uneven shape is formed on the surface of the coating composite material (C) and the organic having almost no uneven shape as in Comparative Examples 5 and 6. It was confirmed that the portion where the compound layer (B) was formed was mixed, and the coating state was different from that of Examples 1 to 5. That is, in Examples 1 to 5, the organic compound layer (B) formed on the surface of the composite material (A) had an uneven shape in almost all regions, whereas in Comparative Example 7, the organic compound layer (B) was formed. Only about 50% had an uneven shape. Also, in the Raman spectrum, unlike Examples 1 to 5 and Comparative Examples 2 to 4, no clear peak was observed at ^{1494 ± 5 cm -1 among the peaks characteristic of the organic compound layer (B) (FIG. 7).} ). It is considered that the structure formed of hydrochloric acid and polyaniline in Comparative Example 7 is different from the structure of polyaniline bonded to phytic acid, which is a phosphoric acid group-containing compound, as in Examples 1 to 5 and Comparative Examples 2 to 4. ..
When the consolidation specific resistance was compared with Examples 1 to 5, the consolidation specific resistance in the low density region was high and could not be measured as in Comparative Example 5.
Compared to Examples 1 to 5, when phytic acid having a plurality of acid functional groups is not used as an acid, even if the organic compound layer (B) covers the composite material (A), it is in a low density region. It was confirmed that the consolidation ratio resistance was higher than that of Examples 1 to 5.

From the above results, if the type of acid and the range of its addition amount are not properly selected, the organic compound layer (B) does not show conductivity, and the organic compound layer (B) makes the composite material (A) good. It was confirmed that the coating could not be performed, the compaction specific resistance of the obtained coated composite particles (C) in the low density region became high, and the effect of reducing the resistance could not be obtained.

Various physical properties were measured for the obtained coated composite particles. The results are shown in the table.

From the table, the coated composite particles (C) of Examples 1 to 5 are coated composite particles (C) in which the surface of the composite material (A) containing a carbon material and silicon is coated with an organic compound layer (B). It was confirmed that the surface roughness Sq of the coated composite particle (C) had irregularities of 12 to 23 nm, and ^{the electric resistance at a low density (0.8 g / cm 3} or less) was lowered.

Claims (9)

The surface of the composite material (A) containing the carbon material and silicon is the coated composite particles (C) coated with the organic compound layer (B) containing polyaniline.
The coated composite having a nitrogen atom content of 0.2 to 0.7% by mass and a phosphorus atom content of 0.08 to 0.6% by mass in the organic compound layer (B) with respect to the coated composite particles (C). particle. The coated composite particle according to claim 1, wherein the coated composite particle (C) has a nitrogen atom content of 0.4 to 3.6% by mass and a phosphorus atom content of 0.08 to 9.6% by mass. The coated composite particle according to claim 2, wherein the coated composite particle (C) has a nitrogen atom content of 0.5 to 1.2% by mass and a phosphorus atom content of 0.08 to 0.6% by mass. The coated composite particle according to any one of claims 1 to 3, wherein the phosphorus atom of the coated composite particle (C) is derived from a compound having a plurality of phosphoric acid groups. The coated composite particle according to any one of claims 1 to 4, wherein the phosphorus atom of the organic compound layer (B) is derived from phytic acid. The coated composite particle according to any one of claims 1 to 5, wherein the nitrogen atom of the organic compound layer (B) is derived from polyaniline. The coated composite particle according to claim 6, wherein in the organic compound layer (B), polyaniline and phytic acid are bonded. The organic compound layer (B), in the Raman ^{spectroscopy, 1475~1525cm -1, 1140~1190cm -1,} has a peak in any of the wavenumber range 785～835Cm ^-1, more of claims 1 to 7 The coated composite particle according to item 1. The organic compound layer (B), in the Raman ^{spectroscopy, 1592 ± 5cm -1, 1494 ±} 5cm -1, a peak to each wave number range of 1165 ± ^{5 cm -1} and 806 ± ^{5 cm -1,} claim The coated composite particle according to any one of 1 to 7.

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