JP6451340B2 - Composite and production method thereof - Google Patents

Description

  The present invention relates to a composite and a method for producing the same, and more particularly to a composite in which pores are specifically filled with silicon and a method for producing the same.

  A composite made of a plurality of different materials may exhibit different characteristics compared to the case where each component is present alone. In particular, composites in which different types of materials are filled in the pores of the porous body are electrically restricted compared to the case where different types of materials exist alone because the different types of materials are physically constrained by the inner walls of the pores. And chemical properties often change.

Various proposals have been made for such composites.
For example, Non-Patent Document 1 discloses a method for obtaining a mixture of crystalline Si and amorphous SiO _x by reducing mesoporous silica with Mg vapor at 650 ° C., washing with 1N HCl, and removing MgO. Is disclosed.
Further, the same document discloses a method of obtaining a composite of carbon and Si / SiO _x by dispersing the mixture in a phenol resin diluted with a solvent and firing the mixture at 800 ° C. in an Ar atmosphere. .

  Non-Patent Document 2 discloses that mesoporous carbon is synthesized by synthesizing a phenol resin from a phenol resin precursor in the presence of crystalline silicon nanoparticles and a triblock copolymer surfactant F127, and further carbonizing the phenol resin. A method for obtaining a composite of Si and Si is disclosed.

As described in Non-Patent Document 1, when mesoporous silica is heated in Mg vapor, a part of the silica constituting the pore wall is reduced to silicon. However, in this method, silicon crystallization and particle enlargement tend to proceed, and it is difficult to cover the pore surface of the porous body with a silicon layer.
In the method described in Non-Patent Document 2, the silicon particle size is larger than the pore diameter of carbon. Therefore, silicon cannot be covered with film-like carbon.

  On the other hand, as a method for producing a polysilicon film or an amorphous silicon film, a thermal decomposition CVD method using a gas such as disilane as a raw material, a plasma CVD method, a photo-CVD method, etc. are known and actually put into practical use. . However, when a conventional silicon generation method is applied to a porous body, silicon is formed even outside the pores, and silicon cannot be specifically generated in the pores. Further, since the source gas enters the pores while thermally decomposing or reacting with the porous body, silicon is easily filled only in the surface layer portion of the pores.

Solid State Ionics 220 (2012) 1-6 Nanotechnology 24 (2013) 025902

The problem to be solved by the present invention is to provide a composite in which silicon is specifically present in the pores and substantially no silicon is present outside the pores, and a method for producing the same.
In addition, another problem to be solved by the present invention is to provide a composite in which silicon is uniformly present inside the porous body and a method for producing the same.

In order to solve the above problems, the complex according to the present invention is:
A porous body,
And silicon introduced into the pores of the porous body.

The method for producing a composite according to the present invention includes:
A preparation step of preparing a porous body;
Introducing a vapor of a silicon compound that is liquid at room temperature, or introducing a liquid or solution of the silicon compound into the pores of the porous body;
A siliconization step for converting the silicon compound into silicon in the pores after the introduction step or simultaneously with the introduction step.

  When a silicon compound that is liquid at room temperature is introduced into the porous body using capillary condensation and / or adsorption, the silicon compound can be selectively and uniformly introduced into the pores. Next, after introducing or simultaneously with introduction of the silicon compound into the pores, decomposition, polymerization (siliconization) of the silicon compound occurs when heat, light, radicals, or the like are applied to the silicon compound. As a result, a solid phase of silicon is deposited in the form of a film on the inner wall surface of the pores, or silicon particles are deposited in the pores.

It is an Ellingham figure of an oxide. It is a SEM image of the spherical carbon / silicon composite obtained in Examples 1-6. Is N ₂ adsorption isotherm at 77K of the resulting spherical carbon / silicon complex in Examples 1 to 6 (left), and pore size distribution (right). It is a SEM image of the spherical particle obtained by baking the spherical carbon / silicon composite of Examples 1-6 in the air.

STEM image (FIG. 5A) of the cross section of the spherical carbon / silicon composite obtained in Example 1 (FIG. 5A), mapping of Si element in the same field of view (FIG. 5B), and obtained in Example 5 It is the STEM image (FIG.5 (c)) of the cross section of a spherical carbon / silicon composite, and Si element mapping (FIG.5 (d)) of the same visual field. 2 is an FE-SEM image of a cross section of spherical particles obtained by firing the spherical carbon / silicon composite of Example 1 in air. It is an XRD pattern of the spherical carbon / silicon composite obtained in Examples 1-6.

It is a SEM image of the spherical carbon (radial pore) / silicon complex obtained in Examples 7-15. Is obtained spherical carbon in Example 7-15 (radial pore) / silicon complex of N ₂ adsorption isotherm at 77K (left), and pore size distribution (right). It is a SEM image of the spherical particle obtained by baking the spherical carbon (radial pore) / silicon composite of Examples 7-15 in the air. It is an XRD pattern of the spherical carbon (radial pore) / silicon composite obtained in Examples 7 to 10, 12, 13, and 15.

It is a SEM image of the spherical carbon (radial pore) / silicon composite_body | complex obtained in Examples 16-18. Is obtained spherical carbon in Examples 15 to 17 (radial pore) / silicon complex of N ₂ adsorption isotherm at 77K (left), and pore size distribution (right). It is a XRD pattern of the spherical carbon (radial pore) / silicon complex obtained in Examples 15-18.

2 is a STEM image of the carbon / silicon composite obtained in Examples 19 and 20. FIG. FIG. 7 shows an N ₂ adsorption isotherm (left figure) and a pore diameter distribution (right figure) at 77 K of the carbon / silicon composite obtained in Examples 19 and 20. FIG. It is a SEM image of the silica / silicon composite obtained in Examples 21-24. Is N ₂ adsorption isotherm at 77K of the resulting silica / silicon complex in Example 21-24 (left), and pore size distribution (right).

FIG. 7 shows an N ₂ adsorption isotherm (left figure) and a pore diameter distribution (right figure) at 77 K of the titania / silicon composite obtained in Example 25. FIG. FIG. 7 shows an N ₂ adsorption isotherm at 77 K (left figure) and a pore size distribution (right figure) of the alumina / silicon composite obtained in Example 26. FIG. It is a figure which shows the change of the reversible electric capacity of the spherical carbon / silicon composite body obtained in Example 1, and the silicon porous body obtained in Comparative Example 4.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Complex]
The complex according to the present invention is:
A porous body,
And silicon introduced into the pores of the porous body.

[1.1. Porous material]
[1.1.1. shape]
The porous body refers to a material having a large number of open pores therein. In the present invention, the shape of the porous body is not particularly limited. As a porous body, for example,
(A) a bulk material, a film, or particles made of a porous material;
(B) an aggregate of porous particles,
(C) There are aggregates of dense particles that function as pores between the particles.
“Aggregate” refers to particles in which particles are bound together by a relatively weak force (for example, van der Waals force). Examples of the aggregate include secondary particles in which primary particles are aggregated, and an array in which spherical particles are regularly or irregularly arranged.

In the case of producing a composite using the method described later, when a dense particle aggregate is used as the porous body, the gaps between the dense particles function as pores for filling silicon. .
On the other hand, when an aggregate of porous particles is used as the porous body, silicon is preferentially filled into the pores inside the porous particles. Further, when the manufacturing conditions are optimized, silicon hardly precipitates on the surface of the porous particles. This is presumably because the silicon compound is introduced into the pores of the porous particles by capillary condensation or adsorption. Since the introduced silicon compound forms a condensed phase, it has a higher density than the gas phase outside the pores, and the siliconization reaction is likely to proceed.

When the porous body is a film, the thickness is not particularly limited.
Similarly, when the porous body is a particle, its particle diameter and shape are not particularly limited. For example, the porous body may be a spherical particle or may be an amorphous particle.
Among these, the porous body is preferably spherical particles. When a composite composed of spherical particles of a porous material is applied to certain applications, the electrochemical and chemical reactions that occur in and / or between the particles are isotropic compared to the case where the porous material is an amorphous particle. Progress easily.

In the present invention, “spherical” means that when a plurality of (preferably 20 or more) particles produced under the same conditions are observed with a microscope, the average value of sphericity of each particle is 13% or less. It means that. The “sphericity” is an index representing the degree of deviation of the outer shape of each particle from the perfect circle, and the circumscribed circle and the particle with respect to the radius (r ₀ ) of the smallest circumscribed circle in contact with the particle surface. This is a value represented by the ratio (= Δr _max × 100 / r ₀ (%)) of the maximum value (Δr _max ) of the distance in the radial direction from each point on the surface. For example, when a method of polycondensing metal alkoxide is used, spherical particles having a sphericity of 7% or less or 3% or less can be obtained.

When the porous body is a spherical particle, the spherical particle does not necessarily need to be “monodispersed” and may have a large variation in diameter. However, the smaller the variation in the diameter of the spherical particles, the more easily various reactions within and / or between the particles proceed more isotropically. For that purpose, the monodispersity of the spherical particles is preferably 10% or less. The monodispersity is more preferably 5% or less.
Here, the “monodispersity” refers to a value represented by the formula (1).
Monodispersity = (standard deviation of particle diameter) × 100 / (average value of particle diameter) (1)

[1.1.2. material]
The material of the porous body is not particularly limited. Examples of the porous material include carbon, metal oxide, polymer, and metal. The porous body may be made of any one of these materials, or may be made of two or more materials.
Among these, the porous body is preferably carbon or a metal oxide. Since carbon and metal oxides are excellent in chemical stability and heat resistance, they are suitable as porous materials for holding silicon.
Further, the porous body is preferably carbon, and particularly preferably mesoporous carbon. When carbon is used as the porous body, when silicon chemically reacts in the pores, transfer of electrons to silicon is facilitated.

However, when the porous body is made of a metal oxide, a material reduced by Si is not suitable. Therefore, the metal oxide is
(A) SiO ₂ or
(B) an oxide that is more stable than SiO ₂ , that is, an oxide having a negative generation free energy ΔG of oxide and an absolute value larger than that of SiO ₂ (see FIG. 1);
Is preferred.
Examples of oxides more stable than SiO ₂ include TiO ₂ , Ti ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , HfO ₂ , MgO, CaO, SrO, BaO, CeO ₂ , Y ₂ O ₃ , Sc _2. Examples include O ₃ and Li ₂ O.
Among these, the metal oxide is preferably SiO ₂ , TiO ₂ , Al ₂ O ₃ , ZrO ₂ , HfO ₂ , CeO ₂ , or Y ₂ O ₃ . This is because they are relatively stable to H ₂ O and acids.

[1.1.3. pore]
[A. Pore shape]
The shape of the pores of the porous body is not particularly limited as long as silicon can be filled therein. The shape of the pores can take various shapes depending on the material constituting the porous body and the method for producing the porous body. For example, gaps between rods in primary particles, cylindrical pores, slit-type pores, gaps between primary particles, and the like can be pores for filling silicon. The term “gap between rods” as used herein refers to, for example, introducing a carbon source into a cylindrical pore of silica, carbonizing it, and then dissolving and removing silica with hydrofluoric acid to accumulate rod-like carbon in a spherical shape. A porous body is obtained, which means a gap between the carbon rods. The porous body may have radial pores or may not have porous pores.

[B. Pore size, average pore size, and pore size distribution]
The pore diameter of the porous body is not particularly limited as long as silicon can be filled into the pores. However, if the pore diameter becomes too small, it becomes difficult to fill the pores with silicon. Therefore, the average pore diameter is preferably 1 nm or more. The average pore diameter is more preferably 2 nm or more. Here, the “average pore diameter” refers to a pore diameter indicating a peak value of a pore diameter distribution curve obtained by a BJH method or a DFT method from a nitrogen adsorption isotherm.

  On the other hand, if the pore diameter is too large, capillary condensation is less likely to occur or the proportion of the adsorption layer in the pores is reduced. Therefore, there are problems that it takes time to form the silicon phase, and it is easy to form the silicon phase outside the pores. Therefore, the average pore diameter is preferably 100 nm or less. The average pore diameter is more preferably 10 nm or less, and further preferably 4 nm or less.

Furthermore, the pore diameter of the porous body is not necessarily uniform and may vary. However, the narrower the pore size distribution, the more uniform the size of the silicon filled in the pores. Therefore, various reactions within the particles and / or between the particles are likely to proceed more uniformly.
Here, “the pore size distribution is narrow” means that the degree of pore size dispersion (an index indicating variation in pore size distribution) represented by the following equation (2) is small. The pore diameter dispersion degree of the porous body is preferably ½ or less, more preferably ３ or less.
Pore diameter dispersion = Δd _p / d _p (2)
Where Δd _p is the full width at half maximum of the pore size distribution curve,
d _p is the average pore diameter.

[C. Pore volume]
The pore volume of the porous body is not particularly limited. In general, the larger the pore volume, the more silicon can be introduced into the porous body.
In order to introduce a large amount of silicon into the porous body, the pore volume is preferably 0.5 mL / g or more. The pore volume is more preferably 1.0 mL / g or more, and still more preferably 1.4 mL / g or more.

[1.2. silicon]
[1.2.1. Silicon Form]
In the present invention, the silicon in the pore is
(A) a film covering the inner wall surface of the pores of the porous body, and / or
(B) It consists of particles encapsulated in pores.
Whether silicon is in the form of a film or particles mainly depends on the amount of silicon introduced into the pores and the conditions for introducing silicon. In the present invention, silicon is obtained by thermally decomposing (siliconizing) a silicon compound. If the method described later is used, it is considered that silicon is deposited in the form of a film on the inner wall surface of the pores in the initial stage of deposition. In addition, it is considered that the silicon film thickness increases as the amount of silicon compound introduced into the pores increases. Furthermore, it is considered that the higher the temperature of siliconization, the more easily silicon becomes particles.

[1.2.2. Crystal structure]
Silicon in the pores becomes amorphous or polycrystalline. Which crystal structure is taken depends on the manufacturing conditions. In general, the higher the temperature of siliconization (lower), the easier it is for silicon to crystallize (amorphize).

[1.2.3. Weight ratio]
The “weight ratio” of silicon refers to a value represented by the formula (3).
Weight ratio (%) = W _t × 100 / W _c (3)
Where W _t is the total weight of silicon contained in the composite,
W _c is the weight of the complex.

The weight ratio of silicon varies depending on the amount of silicon introduced into the porous body, the composition of the porous body, the porosity of the porous body, and the like. When the method described later is used, the weight ratio of silicon can be controlled in a wide range.
For example, when the porous body is made of carbon, the weight ratio of silicon is 10% to 80%. When the manufacturing conditions are optimized, the weight ratio is 30% or more, or 40% or more.
Further, the weight ratio is affected by the true density of the porous body, and the upper limit value of silicon that can be filled is lower as the porous body has a higher true density and the porous body has a smaller pore volume. When the porous body is made of a metal oxide, the weight ratio of silicon is 5% to 75%. When the manufacturing conditions are optimized, the weight ratio is 25% or more, or 35% or more.

[1.2.4. Inclusion rate]
The “encapsulation ratio” of silicon is the ratio of silicon contained in the pores of the porous body in silicon, and is a value defined by the following equation (4).
Inclusion rate (%) = S _SP × 100 / S _S (4)
However, _SSP is the area of the region where both the silicon and the constituent elements of the porous body are detected,
S _S is the area of the region where the silicon is detected.
The encapsulation rate can be measured by element distribution mapping using an electron microscope (SEM, TEM, STEM) or the like.
The region S _S in which silicon is detected is the sum of “region S _S0 in which only silicon is detected” and “region S _SP in which both silicon and the constituent elements of the porous body are detected”. Therefore, if there is no region S _S0 where only silicon is detected or if it is negligibly small, the inclusion rate is 100%.

Silicon may be present on the surface of the porous body in addition to the pores. However, silicon deposited outside the pores is not protected by the porous body. For this reason, when the composite is used for various purposes, it is not possible to suppress deterioration of silicon characteristics. Therefore, it is preferable that most of the silicon exists in the pores.
In order to obtain a composite with little characteristic deterioration, the encapsulation rate is preferably 85% or more. The encapsulation rate is more preferably 90% or more, and still more preferably 95% or more.

[1.2.5. Filling rate]
The “filling rate” of silicon is the ratio of pores in which silicon is detected in the pores of the porous body, and is a value defined by the following equation (5).
Filling rate (%) = S _SP × 100 / S _P (5)
However, _SSP is the area of the region where both the silicon and the constituent elements of the porous body are detected,
_SP is the area of the region where the constituent elements of the porous body are detected.
The filling factor can be measured by element distribution mapping using an electron microscope (SEM, TEM, STEM) or the like.
The region S _P in which the configuration of the porous body is detected is the sum of the “region S _P0 in which only the constituent elements of the porous body are detected” and the “region S _SP in which both the constituent elements of silicon and the porous body are detected”. is there.
Further, when there is no region S _S0 where only silicon is detected or when the region S _S0 is negligibly small, the filling rate is expressed by the following equation (5 ′).
Filling rate (%) = S _S × 100 / S _T (5 ′)
Where S _S is the area of the region where silicon is detected,
_ST is the area of a region where either one of silicon or a constituent element of the porous body is detected.
When S _S0 is substantially zero, S _T is the area of the region indicated by the real image. “A region indicated by a real image” is a region indicated by a secondary electron image, a transmission electron image, or the like that is actually observed with an SEM, TEM, STEM, or the like. The filling rate can be obtained by comparing the real image with the Si element mapping image.
Using the method described later, not only can silicon be introduced specifically and in a large amount into the pores, but also silicon can be introduced uniformly from the surface layer portion to the central portion of the pores. Specifically, the filling rate of silicon into the porous body can be made 70% or more by using the method described later. When the manufacturing conditions are optimized, silicon can be uniformly filled into the pores so that the filling rate is 90% or more. In such a composite that is uniformly filled with silicon, the shape of the porous body can be maintained even after the porous body is removed.

[2. Method for producing composite]
The complex according to the present invention is:
Prepare a porous body,
Introducing a vapor of a silicon compound that is liquid at room temperature, or a liquid or solution of the silicon compound into the pores of the porous body;
It can be produced by converting the silicon compound into silicon in the pores after or simultaneously with the introduction of the silicon compound.

[2.1. Preparation process]
First, a porous body for introducing a silicon compound is prepared. As the porous body, a commercially available one may be used as it is, or a porous body having a target structure may be produced. The method for producing the porous body is not particularly limited, and various methods can be used depending on the material of the porous body, the pore diameter, the pore volume, and the like.

For example, a mesoporous material made of a metal oxide can be produced by polycondensation of a metal alkoxide in the presence of a surfactant.
The mesoporous material made of carbon can be produced by introducing a carbon source into the pores of the mesoporous material made of a metal oxide, carbonizing the carbon source, and removing the metal oxide.
In addition, a porous body made of a polymer, such as microporous 3D polyaniline, is produced by infiltrating aniline into pores of MOF (Metal-Organic Framework), electrolytically polymerizing polyaniline, and further removing MOF. (See Angewandte Chemie International Edition Volume 53, Issure 25, pages 6454-6458, 2014).
The porous body made of metal, for example, drops a precursor solution made of a surfactant, metal ion species, water, and a volatile solvent onto the substrate, volatilizes the solvent to form a liquid crystal, and then deposits the metal. It can be produced by removing the template (see Chemistry of Materials, vol. 19 Issue 6 pages 1335-1342, 2007).

[2.2. Introduction process]
Next, a silicon compound vapor that is liquid at room temperature, or a liquid or solution of the silicon compound is introduced into the pores of the porous body (introduction step).

[2.2.1. Silicon compound]
As the silicon source, a silicon compound that is liquid at room temperature is used. The silicon compound may be a compound that can be polymerized by heat, light, radicals, or the like to generate silicon.
Specifically, the silicon compound is preferably a compound represented by formula (6) or (7), or a polymer or substituted product thereof. Any one of these silicon compounds may be used, or two or more thereof may be used in combination.
The silicon compound is more preferably one or more compounds selected from silicon hydride compounds having one or more cyclic structures. This is because the cyclic silicon hydride compound starts to polymerize at a relatively low temperature than the chain silicon hydride compound due to the cleavage reaction of the cyclic structure, and low molecular volatile components are less likely to be generated during the reaction. is there.

Si _n X _m (6)
However, n is an integer greater than or equal to 3,
m is n, (2n-2), 2n, or (2n + 2),
X is a hydrogen atom and / or a halogen atom.

Si _a X _b Y _c (7)
However, a is an integer greater than or equal to 3,
b is an integer from a to (2a + c + 2),
c is an integer of 1 to a,
X is a hydrogen atom and / or a halogen atom,
Y is a boron atom and / or a phosphorus atom.

The silicon compounds represented by the formulas (6) and (7) are precursor compounds for producing a silicon film, and both have the element X. When the silicon compound having the element X is stimulated by heat, light, radicals, etc., the silicon-hydrogen bond or silicon-halogen bond is cleaved to newly form a silicon-silicon bond. As a result, the silicon compound finally changes to amorphous or polycrystalline silicon.
The halogen atom is usually a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. In terms of bond cleavage, the halogen atom is preferably chlorine or bromine.
Further, the silicon compound represented by the formula (6) or the formula (7) may be a compound containing only a hydrogen atom or a halogen atom as the element X, or a compound containing both (a partially halogenated silicon compound). good.

[2.2.2. Specific examples of silicon compounds]
[A. (6) Silicon compound of formula]
(6) Examples of the silicon compound represented by the formula, or a polymer or substitution product thereof are as follows.
[A. 1. m n = 2n−2 Si _n X _m ]
m = a 2n-2 Si _n X _m, or as a polymer thereof or substitutions,
(A) a silicon hydride compound having two ring systems;
(B) a silicon compound in which part or all of the hydrogen atoms of the silicon hydride compound are substituted with SiH ₃ groups or halogen atoms,
(C) the polymer of (a) or (b) above,
and so on.

As such a compound, for example,
(I) 1,1′-biscyclobutasilane, 1,1′-biscyclopentasilane, 1,1′-biscyclohexasilane, 1,1′-biscycloheptasilane,
(Ii) 1,1′-cyclobutasilylcyclopentasilane, 1,1′-cyclobutasilylcyclohexasilane, 1,1′-cyclobutasilylcycloheptasilane, 1,1′-cyclopentasilylcyclohexasilane 1,1′-cyclopentasilylcycloheptasilane, 1,1′-cyclohexasilylcycloheptasilane,
(Iii) Spiro [2,2] pentasilane, spiro [3,3] heptasilane, spiro [4,4] nonasilane, spiro [4,5] decasilane, spiro [4,6] undecasilane, spiro [5,5] undecasilane , Spiro [5,6] dodecasilane, spiro [6,6] tridecasilane, and the like.

[A. 2. m = 2n, Si _n X _m ]
As Si _n X _m in which m = 2n, or a polymer or substitution product thereof,
(A) a hydrogenated cyclic silicon compound,
(B) a halogenated cyclic silicon compound obtained by substituting a part or all of the hydrogen atoms of the hydrogenated cyclic silicon compound with a halogen atom,
(C) the polymer of (a) or (b) above,
and so on.

  Examples of the hydrogenated cyclic silicon compound include cyclotrisilane, cyclotetrasilane, cyclopentasilane, silylcyclopentasilane, cyclohexasilane, silylcyclohexasilane, and cycloheptasilane.

Examples of the halogenated cyclic silicon compound include:
(I) hexachlorocyclotrisilane, trichlorocyclotrisilane, octachlorocyclotetrasilane, tetrachlorocyclotetrasilane, decachlorocyclopentasilane, pentachlorocyclopentasilane, dodecachlorocyclohexasilane, hexachlorocyclohexasilane, Tetradecachlorocycloheptasilane, heptachlorocycloheptasilane,
(Ii) Hexabromocyclotrisilane, tribromocyclotrisilane, pentabromocyclotrisilane, tetrabromocyclotrisilane, octabromocyclotetrasilane, tetrabromocyclotetrasilane, decabromocyclopentasilane, pentabromocyclopentasilane , Dodecabromocyclohexasilane, hexabromocyclohexasilane, tetradecabromocycloheptasilane, heptabromocycloheptasilane,
and so on.

[A. 3. M _n = 2n + 2 Si _n X _m ]
As Si _n X _m where m = 2n + 2, or a polymer or substitution product thereof,
(A) hydrogenated silane,
(B) a polymer obtained by ring-opening polymerization of a hydrogenated cyclic silicon compound or halogenated cyclic silicon compound represented by Si _n X _2n by heat, light, a radical, or the like;
(C) a compound in which part or all of the hydrogen atoms of the hydrogenated silane or the polymer are substituted with halogen atoms,
(D) the polymer of any one of (a) to (c) above,
and so on.
Examples of the hydrogenated silane include trisilane, tetrasilane, pentasilane, hexasilane, and heptasilane.

[A. 4). m = n and Si _n X _m ]
As Si _n X _m where m = n, or a polymer or substitution product thereof,
(A) a silicon hydride compound having a polycyclic system,
(B) a silicon compound in which part or all of the hydrogen atoms of the silicon hydride compound having a polycyclic system are substituted with Si ₃ H groups or halogen atoms,
(C) the polymer of (a) or (b) above,
and so on.

Examples of the silicon hydride compound having a polycyclic system include the following compounds 1 to 5.

[B. (7) Silicon compound of formula]
(7) As a silicon compound represented by the formula, or a polymer or substituted product thereof,
(A) a modified silane compound with boron,
(B) a modified silane compound with phosphorus,
(C) the polymer of (a) or (b) above,
and so on.

Examples of the modified silane compound with boron include the following compounds 6 to 27. Here, n in the compounds 8, 9, 10, 18, 19, and 20 represents an integer of 0 or more. M in the compounds 26 and 27 represents an integer of 2 or more.
Examples of the modified silane compound with phosphorus include compounds having the same skeleton except that B is replaced with P in the following compounds 6 to 27.

  The above-mentioned modified silane compounds may be used alone, or may be used by mixing with the above-mentioned unmodified silane compounds. The mixing ratio of the modified silane compound and the unmodified silane compound varies depending on the content of the modified element such as boron or phosphorus, but a ratio of the modified element to about 1 ppb to 25% with respect to the silicon atom is preferable.

[2.2.3. Viscosity of liquid or solution]
As described later, the silicon compound is introduced into the pores of the porous body in a vapor, liquid, or solution state. When the liquid silicon compound is introduced into the pores of the porous body, the liquid can be permeated into the pores of the porous body as it is when the viscosity of the liquid is sufficiently low.
On the other hand, when the viscosity of the liquid is too high, it becomes difficult to permeate the liquid into the pores of the porous body. In such a case, it is preferable to dilute the silicon compound with a solvent to obtain a solution. Dilution with a solvent can also be used to reduce the amount of silicon compound introduced into the pores.

In general, the higher the viscosity of the liquid or solution, the more difficult it is to introduce a silicon compound into the pores. Therefore, the viscosity of the liquid or solution is preferably 2500 mPa · s or less.
In addition, the lower the viscosity of the liquid or solution, the easier it is to introduce the silicon compound uniformly into the pores. In order to uniformly introduce the silicon compound into the pores, the viscosity of the liquid or solution is preferably 100 mPa · s or less.

[2.2.4. solvent]
When the silicon compound is diluted with a solvent, the solvent may be any solvent that can dissolve the silicon compound and does not react with the silicon compound. As the solvent, for example,
(A) a hydrocarbon solvent,
(B) an ether solvent,
(B) There are polar solvents and the like. These solvents may be used alone or in combination of two or more.

Of these, hydrocarbon solvents or ether solvents are preferred from the viewpoint of the solubility of the silicon compound and the stability of the solution.
Further, the hydrocarbon solvent has an effect of improving the solubility of the silicon compound and suppressing the residual of the silicon compound during heat treatment and light treatment described later. Therefore, the solvent is particularly preferably a hydrocarbon solvent.

  Examples of the hydrocarbon solvent include n-heptane, n-octane, decane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydronaphthalene, cyclohexylbenzene, cyclohexane and cyclooctane.

  Examples of ether solvents include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether. , P-dioxane and the like.

  Examples of the polar solvent include propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, and cyclohexanone.

[2.2.5. Method for introducing silicon compound]
[A. Introduction of steam]
The silicon compound may be introduced into the pores of the porous body in a vapor state. When the porous body is exposed to silicon compound vapor, the pores are filled with the silicon compound by adsorption. In general, on a smooth surface without pores, the adsorbed material liquefies when its partial pressure (P _ad ) reaches a saturated vapor pressure (P _v ). On the other hand, if there is pores, P _ad is to occur capillary condensation be less than P _v. That is, phase transition occurs at a partial pressure (P _cc ) lower than P _v and the pores are filled with the adsorbent.

In the case where the silicon compound is vaporized and introduced into the pores of the porous body in the vapor state, in the region where the partial pressure (P _ad ) of the adsorbent is lower than P _cc (P _ad <P _cc ), the pore surface An adsorbed layer is formed on the surface, but capillary condensation does not occur. Therefore, the pores are not filled with the adsorbing substance.
On the other hand, in the region where the partial pressure (P _ad ) of the adsorbed material is P _cc or more (P _ad ≧ P _cc ), capillary condensation occurs and the pores are filled with the liquid phase of the silicon compound. That is, the introduction state of the silicon compound can be controlled by the partial pressure.

[B. Introduction of liquid or solution]
The silicon compound may be introduced into the pores of the porous body in a liquid or solution state. When the porous body is brought into contact with the liquid or solution of the silicon compound, capillary condensation occurs, and the pores are filled with the silicon compound. The vapor pressure (P _ad ) of the silicon compound in the liquid state coexistence is about the saturated vapor pressure (P _v ), and the relationship of P _{ad to} P _v > P _cc is established.

[C. advantage]
The advantage of utilizing capillary condensation and / or adsorption in such pores is
(A) a silicon compound condensation layer (adsorption layer or liquid phase) can be formed only in the pores; and
(B) Due to the large density difference from the gas phase existing outside the pores, siliconization can proceed only with the condensed layer, and as a result, silicon formation within the pores can be preferentially caused,
It is.

In pyrolysis CVD and plasma CVD methods, low boiling point silicon compounds such as silane and disilane are often used. However, when a silicon compound having a low boiling point is used, the adsorption layer is not formed at the processing temperature for forming silicon, or the thickness of the adsorption layer becomes very thin even if formed. Therefore, the density difference between the silicon compounds inside and outside the pores becomes small, and it becomes difficult to selectively introduce silicon into the pores.
Therefore, in order to selectively generate silicon in the pores, it is preferable that the silicon compound has a relatively high boiling point (specifically, 150 ° C. or higher). The silicon compound preferably has a small difference between the siliconization treatment temperature and the boiling point, and particularly preferably has a siliconization treatment temperature lower than the boiling point.

[2.3. Siliconization process]
Next, the silicon compound is converted into silicon in the pores (siliconization step). Examples of the method for converting a silicon compound into silicon include heat treatment, light treatment, and radical treatment. For siliconization, any one of these methods may be used, or two or more methods may be used in combination. Siliconization may be performed after the silicon compound is introduced into the pores, or may be performed simultaneously with the introduction.

[2.3.1. Heat treatment]
When the porous body into which the silicon compound is introduced is heat-treated at a predetermined temperature, the silicon compound can be converted into silicon. In the case of heat treatment, amorphous silicon is generally obtained at an ultimate temperature of about 600 ° C. or lower. At higher temperatures, polycrystalline silicon is obtained.
However, if the ultimate temperature is too low, the thermal decomposition of the silicon compound does not proceed sufficiently, and silicon may not be formed. Accordingly, when it is desired to obtain amorphous silicon, the ultimate temperature is preferably 300 ° C. to 600 ° C. The ultimate temperature is more preferably 350 ° C. to 600 ° C.

The atmosphere during the heat treatment is preferably a non-oxidizing atmosphere. As a non-oxidizing atmosphere, for example,
(A) Inert gas atmosphere such as nitrogen, helium, argon,
(B) There is a reducing gas atmosphere in which a reducing gas such as hydrogen is mixed in an inert gas.

  The heat treatment may be performed after the silicon compound is introduced into the porous body, or may be performed at the time of introduction. If the temperature of the porous body is set to 300 ° C. or more when the silicon compound is introduced into the porous body, siliconization can be promoted simultaneously with the introduction of the silicon compound.

[2.3.2. Light processing]
When the porous body into which the silicon compound is introduced is irradiated with light, the silicon compound can be converted into silicon. Examples of light used for light processing include discharge light and laser light.
Examples of the light source for the discharge light include a low-pressure or high-pressure mercury lamp, a deuterium lamp, or a rare gas fluorescent lamp such as argon, krypton, or xenon.
Examples of the laser light source include a YAG laser, an argon laser, a carbon dioxide laser, or an excimer laser such as XeF, XeCl, XeBr, KrF, KrCl, ArF, and ArCl.

As these light sources, those having an output of 10 to 5000 W are generally used, but 0.1 to 1000 W is usually sufficient as the light source used for the optical processing. The wavelength of these lights is not particularly limited as long as the silicon compound absorbs even a little, but is usually 170 nm to 600 nm. In light of absorption efficiency, the wavelength is particularly preferably 170 nm to 420 nm.
The temperature during the light treatment is usually room temperature to 500 ° C. The atmosphere during the light treatment is preferably a non-oxidizing atmosphere.

When the silicon compound solution is introduced into the porous body, the light treatment can be performed either before removing the solvent or after removing the solvent.
Further, heat treatment may be performed after the light treatment or simultaneously with the light treatment. A silicon compound that is soluble in a solvent is converted into silicon having excellent optical characteristics and electrical characteristics by performing heat treatment after the light treatment or simultaneously with the light treatment.
Further, after the amorphous silicon is formed by heat treatment at a low temperature, further light treatment may be performed. When the amorphous silicon is irradiated with light, the amorphous silicon is converted into polycrystalline silicon. The use of laser light is particularly preferable in terms of conversion efficiency.

[2.3.3. Radical treatment]
When a silicon compound is converted into silicon by heat treatment, when a radical initiator is present, radicals are generated at a lower temperature, and the siliconization temperature can be lowered. In particular, when a cyclic silicon compound is used as the silicon compound, the ring-opening reaction is promoted by radicals, and the effect of adding a radical initiator is high.

The radical initiator is not particularly limited as long as it can promote siliconization. As an initiator, for example,
(A) an azo compound such as azobisisobutyronitrile,
(B) Organic peroxides such as di-ter-butyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and methyl ethyl ketone peroxide. All of these are suitable as radical initiators used in the present invention because the decomposition products can be easily removed after use.
The radical initiator may be mixed with the silicon compound and introduced into the pores simultaneously with the silicon compound, or may be introduced prior to the introduction of the silicon compound.

[3. Action]
When a silicon compound that is liquid at room temperature is introduced into the porous body using capillary condensation and / or adsorption, the silicon compound can be selectively and uniformly introduced into the pores. Next, after introducing or simultaneously with introduction of the silicon compound into the pores, decomposition, polymerization (siliconization) of the silicon compound occurs when heat, light, radicals, or the like are applied to the silicon compound. As a result, a solid phase of silicon is deposited in the form of a film on the inner wall surface of the pores, or silicon particles are deposited in the pores.

In addition, when silicon compound is introduced into the pores by using adsorption, when excessive silicon compound vapor exists in the system, the silicon is deposited on the inner wall surface of the pores. The silicon compound vapor is supplied into the pores. The silicon compound newly supplied into the pores is adsorbed on the surface of the already deposited silicon solid phase to form a new adsorption layer. By repeating this, the thickness of the solid phase of silicon increases. That is, the thickness of the solid phase of silicon produced can be controlled by the amount of silicon compound charged into the system.
Similarly, when a silicon compound is introduced into pores using capillary condensation, the thickness of the solid phase of silicon can be controlled by repeatedly introducing the silicon compound into the pores and siliconizing.

In the present invention, since the vapor, liquid or solution of the silicon compound is introduced into the pores of the porous body, the pores are not blocked when the silicon compound is introduced. Therefore, compared with the conventional method, the inside of the porous body can be filled with silicon at a high concentration.
Further, when the method according to the present invention is used, the inner wall surface of the pore can be covered with film-like silicon, or amorphous silicon can be generated in the pore.
Furthermore, since silicon is introduced into the pores by utilizing capillary condensation or adsorption, there is little silicon deposited outside the pores.

  For example, when the porous body is mesoporous carbon, the composite according to the present invention can be used as a negative electrode material for a lithium secondary battery. In the composite according to the present invention, since silicon is in contact with carbon having a high specific surface area, the transfer of electrons to silicon easily proceeds, and the electrolyte can penetrate into the pores. It is also advantageous for the exchange of ions. Furthermore, since carbon contains silicon, even if silicon undergoes a large volume change due to charging / discharging, it is possible to prevent silicon from being pulverized and coming off from carbon. Therefore, a relatively high reversible electric capacity can be secured and the recycling characteristics are also improved.

(Examples 1-2)
[1. Preparation of sample]
[1.1. Example 1]
[1.1.1. Production of spherical carbon porous body]
Using the method described in Reference 1, a spherical carbon porous body (not radial pores) having an average pore diameter of 3.3 nm was obtained.
[Reference 1] Micorporous and Mesoporous Materials, vol. 158, p. 257-263 (Aug. 1 2012)

[A. Preparation of spherical mesoporous silica]
That is, hexadecyltrimethylammonium chloride (C ₁₆ TAC): 35.2 g was dissolved in a mixed solvent of purified water: 4229 g and methanol (MeOH): 3580 g, and the mixture was stirred at 25 ° C. Furthermore, tetramethoxysilane (TMOS) diluted with 1M NaOH: 91.2 g and MeOH: 100 g: 75.2 g and 3-aminopropyltrimethoxysilane (APTMS): 4.7 g were added. After stirring for about 8 hours and allowing to stand overnight, filtration and redispersion in purified water were repeated twice. Furthermore, it dried at 45 degreeC and obtained white powder: 54g.

  In 50 mL of 2N HCl, 3 g of the obtained white powder was dispersed by sonication. The white powder dispersion was placed in an autoclave having an inner cylinder with a capacity of 100 mL and hydrothermally treated at 140 ° C. for 3 days. After the hydrothermal treatment, the autoclave was cooled and decompressed to take out the product. Filtration and redispersion of the product in purified water was repeated twice and washed. Furthermore, after drying at 45 ° C., it was fired in the air at 550 ° C. for 6 hours to obtain 1.5 g of monodisperse spherical mesoporous silica (MMSS) having a large pore diameter. In such hydrothermal synthesis with HCl, the symmetry of the pores is lost, so that the obtained MMSS is not radial pores.

[B. Introduction of carbon source and carbonization]
Put a large pore diameter MMSS: 0.5 g in a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) container (capacity: 15 mL), add furfuryl alcohol (FA) to the pore volume, and add silica pores. Infiltrated. This was heat treated at 150 ° C. for 24 hours to polymerize FA, and further heated at 500 ° C. for 6 hours in a nitrogen atmosphere to promote carbonization of FA. After repeating this twice, heat treatment was performed at 900 ° C. for 6 hours in a nitrogen atmosphere to obtain an MMSS / carbon composite.
This composite was immersed in a 12% HF solution for 12 hours to dissolve the silica component. Then, filtration and washing were repeated and further dried at 45 ° C. to obtain a spherical carbon porous body.

  With respect to the obtained spherical carbon porous body, the nitrogen adsorption isotherm at 77K was measured. From the results, the pore volume and average pore diameter were determined. The pore volume of the spherical carbon porous body was 1.52 mL / g. Moreover, the average pore diameter evaluated using BJH method was 3.3 nm.

[1.1.2. Preparation of spherical carbon / silicon composite]
In a glove box controlled in an Ar atmosphere, spherical carbon porous body: 0.2 g was put in a glass bottle. Further, cyclopentasilane (CPS) was added to the glass bottle for the pore volume and allowed to penetrate into the mesoporous carbon. The glass bottle was allowed to stand on a hot plate, and the temperature of the hot plate was heated to 400 ° C. and held for 30 minutes. Thereafter, the temperature was lowered to room temperature to obtain a spherical carbon / silicon composite.

[1.2. Example 2]
In a glove box controlled under an Ar atmosphere, 0.1 g of the spherical carbon / silicon composite obtained in Example 1 was placed in a glass bottle. Further, an amount of CPS corresponding to half of the pore volume of the spherical carbon porous body was added to the glass bottle and allowed to penetrate into the spherical carbon / silicon composite. The glass bottle was allowed to stand on a hot plate, and the temperature of the hot plate was heated to 400 ° C. and held for 30 minutes. Thereafter, the temperature was lowered to room temperature to obtain a spherical carbon / silicon composite into which the CPS liquid was introduced twice.

[2. Test method and results]
[2.1. SEM observation, adsorption isotherm and pore size distribution]
FIG. 2A and FIG. 2B show SEM images of the spherical carbon / silicon composite obtained in Example 1 and Example 2, respectively. FIG. 3 (a) shows N ₂ adsorption isotherms at 77K for these samples. FIG. 3 (b) shows the pore size distribution obtained by using the BJH method from the adsorption isotherm of FIG. 3 (a). FIG. 3 also shows the result of the spherical carbon porous body before introducing silicon.

These samples are processed at a temperature equal to or higher than the boiling point of CPS introduced as a liquid. Therefore, when the vapor pressure in the system increases as the temperature rises and the relative pressure becomes _Pcc or less, surplus CPS is once released from the pores, leaving CPS forming the adsorption layer. The Thereafter, when the CPS of the adsorption layer is consumed with siliconization in the pores, a part of the CPS released outside the pores is adsorbed by the pores. In this way, it is considered that introduction of silicon into carbon proceeds.

From the results of SEM observation, it was found that in any sample, the spherical shape was maintained after the silicon introduction treatment, and there was no large precipitation of Si particles outside the sphere (FIG. 2). In addition, with the silicon introduction treatment, the amount of N ₂ adsorbed greatly decreased, and the pore size distribution obtained therefrom also changed significantly (FIG. 3). From these results, it was confirmed that silicon was precipitated in the pores of the spherical carbon porous body.

In Example 2 in which the CPS liquid was introduced twice, the change in the adsorption isotherm was large and almost no nitrogen was adsorbed. Thus, it was found that the amount of silicon introduced can be increased by repeatedly introducing the silicon compound. .
The weight ratio of silicon in the composite (the ratio of silicon in the sample weight) was determined by thermogravimetric analysis. As a result, the weight ratios of silicon were 45.7% (Example 1) and 53.6% (Example 2), respectively (Table 1). Table 1 also shows the results of Examples 3 to 6 described later.

[2.2. Oxidation treatment of complex]
The spherical carbon / silicon composite was fired in air at 550 ° C. for 6 hours. At this time, carbon in the composite is oxidized and removed as CO or CO ₂ gas, and silicon is oxidized and converted to silica. 4 (a) and 4 (b) show SEM images of spherical particles obtained by firing the spherical carbon / silicon composites of Example 1 and Example 2 in air, respectively. Even after the carbon was removed by firing, the spherical shape was maintained, and it was confirmed that a considerable amount of silicon was introduced into the spherical carbon porous body.

[2.3. Cross-sectional observation of composite and evaluation of inclusion rate and filling rate]
In Example 1, in order to observe the introduction state of silicon, a spherical carbon / silicon composite was embedded in a resin and cut into thin pieces. FIG. 5A shows a STEM image of the cut surface of the sample, and FIG. 5B shows mapping of the Si element in the same field of view. Silicon was distributed throughout the spherical particles, and it was confirmed that it was introduced into the spherical carbon porous body. Further, it has been confirmed that silicon is not detected alone but is always detected together with carbon. [1.2.5. ], The inclusion rate is almost 100%, so the filling rate can be calculated by (area of the region where silicon is detected) × 100 / (area of the region shown by the real image). When calculated from FIG. 5A and FIG. 5B, the filling rate was determined to be 96%.
In addition, the fired spherical particles of Example 1 were embedded in a resin to expose the cut surfaces of the spherical particles. In FIG. 6, the FE-SEM image of the cross section of the spherical particle after baking is shown. Silica produced by oxidation of silicon is present up to the inside of the particles, suggesting that silicon has been introduced to the center of the spherical carbon porous body.

[2.4. X-ray diffraction]
Next, in order to investigate the crystalline state of silicon, X-ray diffraction measurement was performed. FIG. 7 shows the XRD pattern of the spherical carbon / silicon composite obtained in Example 1 and Example 2. Since no sharp peak exists in any sample, the obtained silicon state is considered to be amorphous. In addition, since the broad peak near 2θ = 28 ° derived from amorphous silicon is clearer in Example 2, it was found that the amount of amorphous silicon generated is increased by repeatedly introducing CPS. .

(Examples 3 to 4, Comparative Example 1)
[1. Preparation of sample]
[1.1. Example 3]
[1.1.1. Production of spherical carbon porous body]
Using the method described in Reference Document 1 above, a spherical carbon porous body having an average pore diameter of 6.2 nm was obtained.

That is, C ₁₆ TAC: 35.2 g was dissolved in a mixed solvent of purified water: 4126 g and MeOH: 3810 g, and the mixture was kept at 25 ° C. and stirred. Further, 26.4 g of TMOS diluted with 34.2 g of 1M NaOH and 30 g of MeOH was added. After stirring for about 8 hours and allowing to stand overnight, filtration and redispersion in purified water were repeated twice. Furthermore, it dried at 45 degreeC and obtained white powder: 17.5g.

  MMSS: 1.5 g was obtained in the same manner as in Example 1 except that 3 g of the obtained white powder was used and the hydrothermal treatment temperature was 150 ° C. Also in this case, since hydrothermal synthesis using HCl is used, the symmetry of the pores is lost with the treatment, and the obtained MMSS is not a radial pore.

  Next, a spherical carbon porous body was obtained in the same manner as in Example 1 using the obtained MMSS. With respect to the obtained spherical carbon porous body, the nitrogen adsorption isotherm at 77K was measured. From the results, the pore volume and average pore diameter were determined. The pore volume of the spherical carbon porous body was 1.90 mL / g. Moreover, the average pore diameter evaluated using BJH method was 6.2 nm.

[1.1.2. Preparation of spherical carbon / silicon composite]
Using the obtained spherical carbon porous body, a spherical carbon / silicon composite was obtained in the same manner as in Example 1 (introduction of CPS liquid).

[1.2. Example 4]
In the same manner as in Example 3, a spherical carbon porous body was obtained. Further, the CPS was irradiated with 365 nm light under the condition of 15 mW / cm ² for 10 minutes to obtain polydihydrosilane. The viscosity of the obtained polydihydrosilane was 5 mPa · s.
Furthermore, a spherical carbon / silicon composite was obtained in the same manner as in Example 3 except that the low-viscosity polydihydrosilane was used instead of CPS as the silicon source.

[1.3. Comparative Example 1]
The CPS was irradiated with 365 nm light for 10 hours under the condition of 50 mW / cm ² to obtain polydihydrosilane. The viscosity of the obtained polydihydrosilane was 3000 mPa · s.
Further, a spherical carbon / silicon composite was tried in the same manner as in Example 4 except that the high-viscosity polydihydrosilane was used as the silicon source.

[2. Test method and results]
[2.1. SEM observation, adsorption isotherm and pore size distribution]
FIGS. 2C and 2D show SEM images of the spherical carbon / silicon composites obtained in Example 3 and Example 4, respectively. FIG. 3 (c) shows N ₂ adsorption isotherms at 77K for these samples. FIG. 3 (d) shows the pore size distribution obtained using the BJH method from the adsorption isotherm obtained in FIG. 3 (c).

  In Example 3, it is considered that silicon is introduced into the pores of the spherical carbon porous body through the same process as in Examples 1 and 2. On the other hand, in Example 4, polydihydrosilane which is a polymer of CPS is used as a silicon source. Since polydihydrosilane does not evaporate, it is not released out of the pores even at the treatment temperature.

In Example 4, the same results as in Examples 1 to 3 were obtained. That is, from the results of SEM observation, it was found that in any sample, the spherical shape was maintained even after the introduction of silicon, and there was no large precipitation of Si particles outside the sphere (FIG. 2). In addition, with the silicon introduction treatment, the amount of N ₂ adsorbed greatly decreased, and the pore size distribution obtained therefrom also changed significantly (FIG. 3). From these results, it was confirmed that silicon was precipitated in the pores of the spherical carbon porous body. The weight ratios of silicon in the composite determined by thermogravimetric analysis were 47.3% (Example 3) and 56.4% (Example 4), respectively (Table 1).

On the other hand, when the sample obtained in Comparative Example 1 was visually confirmed, it was found that a metallic luster lump of a size that could be visually confirmed was present everywhere in the sample. Although the adsorption isotherm of N ₂ (not shown) decreased overall, the pore size distribution hardly changed. When high-viscosity polydihydrosilane was used, it was found that polydihydrosilane did not penetrate into the pores, making it difficult to introduce silicon into the spherical carbon porous body.

[2.2. Oxidation treatment of complex]
FIGS. 4C and 4D show SEM images of spherical particles obtained by firing the spherical carbon / silicon composites of Example 3 and Example 4 in air, respectively. Even after removing the carbon by firing, the spherical shape was maintained, and it was confirmed that a considerable amount of silicon was introduced into the spherical carbon.

[2.3. X-ray diffraction]
FIG. 7 shows the XRD pattern of the spherical carbon / silicon composite obtained in Example 3 and Example 4. From FIG. 7, it was found that the generated silicon was amorphous.
From the above, it was found that silicon can be introduced into the pores of the spherical carbon porous body even when polydihydrosilane which is a polymer of CPS is used.

(Examples 5-6)
[1. Preparation of sample]
[1.1. Example 5]
MMSS: 1.5 g was obtained in the same manner as in Example 1 except that the hydrothermal treatment temperature was 130 ° C. Using the obtained MMSS as a mold, a spherical carbon porous body was obtained in the same manner as in Example 1. The pore volume of the spherical carbon porous body was 1.52 mL / g. Moreover, the average pore diameter evaluated using BJH method was 3.0 nm.
Next, using this spherical carbon porous body, in the same manner as in Example 1, introduction of CPS liquid and heat treatment at 400 ° C. were performed to obtain a spherical carbon / silicon composite. Furthermore, this spherical carbon / silicon composite was heat-treated in an argon atmosphere at 600 ° C. for 1 hour.

[1.2. Example 6]
As in Example 5,
(A) introduction of CPS liquid and heat treatment at 400 ° C., and
(B) A spherical carbon / silicon composite that was heat-treated in an argon atmosphere at 600 ° C. for 1 hour was obtained. Furthermore, this spherical carbon / silicon composite was heat-treated in an argon atmosphere at 800 ° C. for 1 hour.

[2. Test method and results]
[2.1. SEM observation, adsorption isotherm and pore size distribution]
FIG. 2 (e) and FIG. 2 (f) show SEM images of the spherical carbon / silicon composites obtained in Example 5 and Example 6, respectively. FIG. 3 (e) shows N ₂ adsorption isotherms at 77K for these samples. FIG. 3 (f) shows the pore size distribution obtained using the BJH method from the adsorption isotherm obtained in FIG. 3 (e).

In Examples 5 and 6, the effect of further heat treatment on the spherical carbon / silicon composite produced in substantially the same manner as in Example 1 was examined.
From the results of SEM observation, it was found that Si did not precipitate outside the sphere with the heat treatment at 600 ° C. or 800 ° C. (FIG. 2). On the other hand, it was found that the sample heat-treated at 800 ° C. had a slightly increased amount of N ₂ adsorbed and the amount of silicon decreased compared to the sample heat-treated at 600 ° C. The weight ratios of silicon in the composite determined by thermogravimetric analysis were 40.9% (Example 5) and 38.6% (Example 6), respectively (Table 1).

[2.2. Oxidation treatment of complex]
FIGS. 4 (e) and 4 (f) show SEM images of spherical particles obtained by firing the spherical carbon / silicon composites of Example 5 and Example 6 in air, respectively. Even after removing the carbon by firing, the spherical shape was maintained, and it was confirmed that a considerable amount of silicon was introduced into the spherical carbon porous body.

[2.3. Cross-sectional observation of composite and evaluation of inclusion rate and filling rate]
For Example 5, as in Example 1, in order to observe the state of silicon introduction, a spherical carbon / silicon composite was embedded in a resin and cut into thin pieces. FIG. 5C shows a STEM image of the cut surface of the sample, and FIG. 5D shows Si element mapping in the same field of view. Silicon was distributed throughout the spherical particles, and it was confirmed that it was introduced into the spherical carbon porous body. Further, it has been confirmed that silicon is not detected alone but is always detected together with carbon. [1.2.5. ], The inclusion rate is almost 100%, so the filling rate can be calculated by (area of the region where Si is detected) × 100 / (area of the region shown by the real image). When calculated from FIG. 5C and FIG. 5D, the filling rate was determined to be 98%.
[2.4. X-ray diffraction]
FIG. 7 shows XRD patterns of the spherical carbon / silicon composite obtained in Example 5 and Example 6. The sample heat-treated at 600 ° C. did not change much in the XRD pattern compared to the sample before heat treatment. On the other hand, in the sample heat-treated at 800 ° C., a slightly sharper peak was observed, and some crystallization was confirmed.
From the above, it was found that in the sample heat-treated at 600 ° C., silicon remained amorphous, but in the sample heat-treated at 800 ° C., a part of silicon was crystallized.

(Examples 7 to 15)
[1. Preparation of sample]
[1.1. Example 7]
Using the method described in Reference 2 (Japanese Patent Laid-Open No. 2006-219322), monodispersed spherical mesoporous carbon having pores with an average pore diameter of 1.1 nm was obtained.

That is, C ₁₆ TAC: 7.04 g was dissolved in a mixed solvent of purified water: 809.2 g and MeOH: 754 g, and the mixture was kept at 25 ° C. and stirred. Further, tetraethoxysilane (TEOS) diluted with 1M NaOH: 6.84 g and MeOH: 30 g: 7.23 g was added. After stirring for about 8 hours and allowing to stand overnight, filtration and redispersion in purified water were repeated twice. Furthermore, it dried at 45 degreeC and obtained white powder: 3.65g.
Further, this white powder was baked in the atmosphere at 550 ° C. for 6 hours to obtain monodispersed spherical mesoporous silica particles (MMSS) having a particle size of 0.66 μm. The MMSS obtained by this method has radial pores.

Next, using the obtained MMSS as a template, a spherical carbon porous body was obtained in the same manner as in Example 1. The pore volume of the obtained spherical carbon porous body was 0.78 mL / g. Moreover, the average pore diameter evaluated using DR method was 1.1 nm. The spherical carbon porous body obtained by this method has radial pores in order to inherit the symmetry of MMSS.
Further, using this spherical carbon porous body, a spherical carbon / silicon composite was obtained in the same manner as in Example 1 (introduction of CPS liquid).

[1.2. Example 8]
Using the spherical carbon porous body obtained in Example 7, a spherical carbon / silicon composite was obtained in the same manner as in Example 4 (introduction of polydihydrosilane liquid).
[1.3. Example 9]
Using the spherical carbon porous body obtained in Example 7, a spherical carbon / silicon composite was obtained in the same manner as in Example 2 (CPS liquid introduced twice).

[1.4. Example 10]
Using the method described in Reference Document 2 above, a monodispersed spherical carbon porous body having pores with an average pore diameter of 1.9 nm was obtained.

That is, C ₁₆ TAC: 35.2 g was dissolved in a mixed solvent of purified water: 4126 g and MeOH: 3810 g, and the mixture was kept at 25 ° C. and stirred. Further, 26.4 g of TMOS diluted with 34.2 g of 1M NaOH and 30 g of MeOH was added. After stirring for about 8 hours and allowing to stand overnight, filtration and redispersion in purified water were repeated twice. Furthermore, it dried at 45 degreeC and obtained white powder: 17.5g.

  In a mixed solvent of purified water: 60 mL and EtOH: 60 mL, 2 g of the obtained white powder was dispersed by ultrasonic treatment, and further trimethylbenzene (TMB): 10 g was added and stirred. The white powder dispersion was placed in an autoclave having an inner cylinder with a capacity of 200 mL and hydrothermally treated at 100 ° C. for 3 days. After the hydrothermal treatment, the autoclave was cooled and decompressed to take out the product. The product was filtered and redispersed in EtOH twice and washed. Furthermore, after drying at 45 ° C., it was fired in the air at 550 ° C. for 6 hours to obtain a large pore diameter MMSS: 0.79 g.

Next, a spherical carbon porous body was obtained in the same manner as in Example 1 except that the obtained large pore diameter MMSS was used as a template. The pore volume of the obtained spherical carbon porous body was 0.97 mL / g. Moreover, the average pore diameter evaluated using BJH method was 1.9 nm.
Further, using this spherical carbon porous body, a spherical carbon / silicon composite was obtained in the same manner as in Example 1 (introduction of CPS liquid).

[1.5. Example 11]
A spherical carbon / silicon composite was obtained in the same manner as in Example 4 (introduction of a polydihydrosilane liquid) except that the spherical carbon porous body obtained in Example 10 was used.

[1.6. Example 12]
Using the spherical carbon porous body obtained in Example 10, CPS vapor was introduced into the pores by the following method to obtain a spherical carbon / silicon composite.

That is, a sample bottle containing 0.2 g of spherical carbon porous body and a sample bottle containing CPS of 3 times the pore volume of the spherical carbon porous body are in contact with each other at the bottom of a sealed container (20 mL). Placed and sealed.
Next, after the sealed container was left on the hot plate, the temperature of the hot plate was heated to 400 ° C. and held for 30 minutes. Thereafter, the temperature was lowered to room temperature to obtain a spherical carbon / silicon composite.

[1.7. Example 13]
By using the method described in Reference 3 (Japanese Patent Laid-Open No. 2010-265125), a monodispersed spherical carbon porous body having pores having an average pore diameter of 3.8 nm was obtained.

That is, C ₁₆ TAC: 35.2 g was dissolved in a mixed solvent of purified water: 4126 g and MeOH: 3810 g, and the mixture was kept at 25 ° C. and stirred. Further, TMOS diluted with 1M NaOH: 34.2 g and MeOH: 30 g: 23.76 g and APTMS: 3.11 g were added. After stirring for about 8 hours and allowing to stand overnight, filtration and redispersion in purified water were repeated twice. Then, it dried at 45 degreeC and obtained white powder: 16.5g. Further, the white powder was fired at 550 ° C. for 6 hours in the air.

Using the obtained white powder, a spherical carbon porous body was obtained in the same manner as in Example 10. The pore volume of the obtained spherical carbon porous body was 1.42 mL / g. Moreover, the average pore diameter evaluated using BJH method was 3.8 nm.
Further, using this spherical carbon porous body, a spherical carbon / silicon composite was obtained in the same manner as in Example 1 (introduction of CPS liquid).

[1.8. Example 14]
Using the spherical carbon porous body obtained in Example 13, a spherical carbon / silicon composite was obtained in the same manner as in Example 4 (introduction of a polydihydrosilane liquid).
[1.9. Example 15]
Using the spherical carbon porous body obtained in Example 13, a spherical carbon / silicon composite was obtained in the same manner as in Example 12 (introduction of CPS vapor).

[2. Test method and results]
In Examples 7 to 15, the influence of the pore diameter of the spherical carbon porous body was mainly examined using the spherical carbon porous body having radial pores.
[2.1. Examples 7 to 9]
In each of Examples 7 to 9, a spherical carbon porous body having an average pore diameter of 1.1 nm having radial pores is used. On the other hand, in Example 7, CPS was introduced into the pores in a liquid state, and in Example 8, polydihydrosilane, which is a polymer of CPS, was introduced into the pores in a liquid state. Further, in Example 9, CPS was further introduced in a liquid state into the pores of the spherical carbon / silicon composite prepared in Example 7.

[2.1.1. SEM observation, adsorption isotherm and pore size distribution]
FIG. 8 shows SEM images of the spherical carbon (radial pore) / silicon composite obtained in Examples 7-9. FIG. 9 shows the N ₂ adsorption isotherm of these samples at 77K and the pore size distribution obtained from this adsorption isotherm using the BJH method. FIG. 9 also shows the result of the spherical carbon porous body before introducing silicon.

From the results of SEM observation, it was found that in any sample, the spherical shape was maintained after the silicon introduction treatment, and there was no large precipitation of Si particles outside the sphere (FIG. 8). In addition, the amount of N ₂ adsorbed significantly decreased with the silicon introduction process (FIG. 9). In this pore size region, the calculation of the pore diameter distribution by the BJH method lacks accuracy, so it is difficult to determine the peak position from FIG. However, since the mesopores of 2 nm or more are greatly reduced, it is considered that silicon is being introduced into the pores.

Since the same results as in Example 4 were obtained in the samples of Examples 7 to 9, the CPS liquid or polydiene was also used for spherical carbon porous bodies having radial pores with an average pore diameter of 1.1 nm. It has been found that silicon can be introduced into the pores using a hydrosilane liquid. It was also found that the amount of silicon introduced can be increased by repeatedly introducing CPS.
The weight percentages of silicon in the composite determined by thermogravimetric analysis were 30.3% (Example 7), 27.2% (Example 8), and 37.2% (Example 9), respectively. (Table 2). Table 2 also shows the results of Examples 10 to 15 described later.

[2.1.2. Oxidation treatment of complex]
FIG. 10 shows SEM photographs of spherical particles obtained by firing the spherical carbon / silicon composites of Examples 7 to 9 in air. Even in the sample after firing, the spherical shape is maintained, suggesting that silicon is introduced into the entire spherical carbon porous body.

[2.1.3. X-ray diffraction]
FIG. 11 shows the XRD patterns of the spherical carbon / silicon composites obtained in Examples 7-9. The crystallinity of each sample was amorphous. Further, in Example 9 (CPS liquid was introduced twice) in which a relatively large amount of silicon was introduced, a slight amount of halo corresponding to amorphous silicon was observed.

[2.2. Examples 10 to 12]
In Examples 10 to 12, a spherical carbon porous body having radial pores and an average pore diameter of 1.9 nm is used. On the other hand, in Example 10, CPS was introduced into the pores in a liquid state, and in Example 11, polydihydrosilane, which is a polymer of CPS, was introduced into the pores in a liquid state. Furthermore, in Example 12, CPS was introduced into the pores in a vapor state.

[2.2.1. SEM observation, adsorption isotherm and pore size distribution]
FIG. 8 shows SEM images of the spherical carbon (radial pore) / silicon composite obtained in Examples 10-12. FIG. 9 shows the N ₂ adsorption isotherm of these samples at 77K and the pore size distribution obtained from this adsorption isotherm using the BJH method.

For the spherical carbon porous body having an average pore diameter of 1.9 nm, the same result as that of the spherical carbon porous body having an average pore diameter of 1.1 nm was obtained. That is, from the results of SEM observation, it was found that in any sample, the spherical shape was maintained after the silicon introduction treatment, and there was no large precipitation of Si particles outside the sphere (FIG. 8). Further, with the silicon introduction treatment, the amount of N ₂ adsorbed greatly decreased and the pore size distribution also changed significantly (FIG. 9).

Since the same results as in Example 4 were obtained in the samples of Examples 10 to 11, the CPS liquid or polydiene was also used for spherical carbon porous bodies having radial pores with an average pore diameter of 1.9 nm. It has been found that silicon can be introduced into the pores using a hydrosilane liquid.
Further, from the results of Example 12, if CPS vapor can be used to introduce silicon into the pores of the spherical carbon porous body, and if CPS having a volume three times the pore volume is placed in the system, It has been found that silicon can be introduced to the extent that the pores are filled.
The weight ratios of silicon determined by thermogravimetric analysis were 36.2% (Example 10), 27.3% (Example 11), and 39.6% (Example 12), respectively (Table 2). ).

[2.2.2. Oxidation treatment of complex]
FIG. 10 shows SEM photographs of spherical particles obtained by firing the spherical carbon / silicon composites of Examples 10 to 12 in air. Even in the sample after firing, the spherical shape is maintained, suggesting that silicon is introduced into the entire spherical carbon porous body.

[2.2.3. X-ray diffraction]
FIG. 11 shows the XRD pattern of the spherical carbon / silicon composite obtained in Examples 10 and 12. The crystallinity of each sample was amorphous. Further, in Example 12 (CPS vapor was introduced) in which a relatively large amount of silicon was introduced, a halo corresponding to amorphous silicon was slightly observed.

[2.3. Examples 13 to 15]
In Examples 13 to 15, a spherical carbon porous body having radial pores and an average pore diameter of 3.8 nm is used. On the other hand, in Example 13, CPS was introduced into the pores in a liquid state, and in Example 14, polydihydrosilane, which is a polymer of CPS, was introduced into the pores in a liquid state. Furthermore, in Example 15, CPS was introduced into the pores in a vapor state.

[2.3.1. SEM observation, adsorption isotherm and pore size distribution]
FIG. 8 shows SEM photographs of the spherical carbon (radial pore) / silicon composite obtained in Examples 13-15. FIG. 9 shows the N ₂ adsorption isotherm of these samples at 77K and the pore size distribution obtained from this adsorption isotherm using the BJH method.

For the spherical carbon porous body having an average pore diameter of 3.8 nm, the same results as those of the spherical carbon porous body having an average pore diameter of 1.1 nm and 1.9 nm were obtained. That is, from the results of SEM observation, it was found that in any sample, the spherical shape was maintained after the silicon introduction treatment, and there was no large precipitation of Si particles outside the sphere (FIG. 8). Further, with the silicon introduction treatment, the amount of N ₂ adsorbed greatly decreased and the pore size distribution also changed significantly (FIG. 9).

Since the same results as in Example 4 were obtained in the samples of Examples 13 to 15, the CPS liquid or polydiene was also used for the spherical carbon porous body having radial pores having an average pore diameter of 3.8 nm. It has been found that silicon can be introduced into the pores using a hydrosilane liquid.
Further, from the results of Example 15, if CPS vapor is used, silicon can be introduced into the pores of the spherical carbon porous body, and if CPS having a volume three times the pore volume is put in the system. It has been found that silicon can be introduced to the extent that the pores are filled.
The weight percentages of silicon determined by thermogravimetric analysis were 43.2% (Example 13), 38.8% (Example 14), and 58.3% (Example 15), respectively (Table 2). ).

[2.3.2. Oxidation treatment of complex]
FIG. 10 shows SEM images of spherical particles obtained by firing the spherical carbon / silicon composites of Examples 13 to 15 in air. Even in the sample after firing, the spherical shape is maintained, suggesting that silicon is introduced into the entire spherical carbon porous body.

[2.3.3. X-ray diffraction]
FIG. 11 shows the XRD pattern of the spherical carbon / silicon composite obtained in Examples 13 and 15. The crystallinity of each sample was amorphous. Further, in Example 15 (in which CPS vapor was introduced) in which a relatively large amount of silicon was introduced, a halo corresponding to amorphous silicon was clearly observed.

(Examples 16 to 17)
[1. Preparation of sample]
[1.1. Example 16]
A spherical carbon / silicon composite was obtained in the same manner as in Example 15 (introduction of CPS vapor) except that the amount of CPS charged was 1/3 of Example 15 (ie, equivalent pore volume).
[1.2. Example 17]
A spherical carbon / silicon composite was obtained in the same manner as in Example 15 (introduction of CPS vapor) except that the amount of CPS charged was 2/3 of Example 15 (ie, twice the pore volume). .

[2. Test method and results]
[2.1. SEM observation, adsorption isotherm and pore size distribution]
FIG. 12 shows SEM images of the spherical carbon (radial pore) / silicon composite obtained in Examples 16 and 17. FIG. 13 shows the N ₂ adsorption isotherm and pore size distribution of these samples at 77K. FIG. 13 also shows the spherical carbon porous body before introducing silicon and the results of Example 15.

In Examples 16 and 17, in comparison with Example 15, when CPS vapor was introduced into the pores of the spherical carbon porous body, the amount of silicon introduced and the pores of the composite were changed by changing the amount of CPS charged. Indicates that the structure can be controlled.
In these examples, the spherical carbon porous body used and the processing temperature are the same, but the amount of CPS charged into the system is different. The amount of CPS charged under each condition is equal to the pore volume of the spherical carbon porous body (Example 16), 2 times (Example 17), or 3 times (Example 15).

As in the previous examples, from the results of SEM observation, it was confirmed that in all samples, the spherical shape was maintained after the silicon introduction treatment, and there was no large precipitation of Si particles outside the sphere ( FIG. 12). In addition, the amount of silicon introduced increased as the amount of CPS charged increased. The weight ratio of silicon in each sample was 49.4% (Example 16), 54.5% (Example 17), and 58.3% (Example 15), respectively (Tables 2 and 3). ).
From the above results, it was found that the amount of silicon introduced into the spherical carbon porous body can be controlled by changing the amount of CPS charged into the system.

  As the amount of silicon introduced increased, the pore diameter and pore volume decreased. This indicates that silicon is deposited in a film shape on the pore walls of the spherical carbon porous body, and as a result, the pore diameter of the spherical carbon porous body is reduced. Thus, it was found that the (residual) pore diameter of the spherical carbon / silicon composite can be controlled by changing the amount of CPS charged into the system.

[2.2. X-ray diffraction]
FIG. 14 shows an XRD pattern of the spherical carbon / silicon composite obtained in Examples 16 and 17. FIG. 14 also shows the results of the spherical carbon porous body before introducing silicon and Examples 15 and 18.
The crystallinity of each sample was amorphous. In addition, a halo corresponding to amorphous silicon was clearly observed in a sample with a larger amount of silicon introduced.

(Example 18)
[1. Preparation of sample]
Spherical carbon / silicon composite as in Example 17 (CPS vapor introduction, twice the pore volume) except that the temperature of the hot plate at the time of CPS introduction (siliconization treatment temperature) was 600 ° C. Got the body.

[2. Test method and results]
[2.1. SEM observation]
FIG. 12 shows an SEM image of the spherical carbon (radial pore) / silicon composite obtained in Example 18.
Here, the influence of the temperature of the hot plate at the time of introduction of CPS (siliconization processing temperature) on the crystal state is compared between 400 ° C. (Example 17) and 600 ° C. (Example 18).
From the results of SEM observation, it was confirmed that even in Example 18, the spherical shape was maintained even after the introduction of silicon, and there was no large precipitation of Si particles outside the sphere (FIG. 12). The weight percentage of silicon in Example 18 was 54.5% (Table 3).

[2.2. X-ray diffraction]
FIG. 14 shows the XRD pattern of the spherical carbon / silicon composite obtained in Example 18. The crystallinity of the spherical carbon / silicon composite obtained in Example 18 was amorphous. However, the intensity of the halo corresponding to amorphous silicon was higher than in Example 17 where the amount of silicon introduced was similar. This is probably because the treatment at 600 ° C. decreased the Si—H bond and increased the Si—Si bond.
From the above, it has been found that the crystallinity of silicon in the spherical carbon / silicon composite remains amorphous at a processing temperature of about 600 ° C.

(Examples 19 to 20)
[1. Preparation of sample]
[1.1. Example 19]
Polyethylene oxide-polypropylene oxide-polyethylene oxide copolymer: 2 g, purified water: 15 mL, 2N hydrochloric acid: 60 mL were mixed to obtain a transparent solution. TEOS: 4.25g was added to this transparent solution, and it stirred at room temperature for 5 minutes. Then, it left still at 30 degreeC for 24 hours, and also at 100 degreeC for 24 hours, and performed hydrothermal treatment. After the hydrothermal treatment, the autoclave was cooled and decompressed to take out the product. The product was filtered and redispersed in EtOH twice and washed. Furthermore, after drying at 45 ° C., it was calcined in the atmosphere at 550 ° C. for 6 hours to obtain 2 g of mesoporous silica.

  Next, mesoporous carbon was produced in the same manner as in Example 1 using the obtained mesoporous silica. Further, using this mesoporous carbon, a carbon / silicon composite was obtained in the same manner as in Example 1 (introduction of CPS liquid).

[1.2. Example 20]
Using the mesoporous carbon obtained in Example 19, a carbon / silicon composite was obtained in the same manner as in Example 12 (introduction of CPS vapor).

[2. Test method and results]
FIG. 15 shows STEM images of the carbon / silicon composites obtained in Examples 19 and 20. FIG. 16 shows the N ₂ adsorption isotherm of these samples at 77 K and the pore diameter distribution obtained from the adsorption isotherm using the BJH method. FIG. 16 also shows the results of mesoporous carbon before introducing silicon.
The mesoporous carbon used in Examples 19 and 20 has hexagonal symmetry over the entire sample, and is easy to observe with an STEM or the like, and is a sample that makes it easy to grasp the dispersion state of silicon in the mesoporous carbon. By analyzing the carbon / silicon composite obtained in Examples 19 and 20, the dispersion state of silicon in the mesoporous carbon is clarified.

  In the STEM image of FIG. 15, Si having a higher atomic number is whiter and carbon appears darker. In both Examples 19 and 20, a periodic stripe pattern was observed in the longitudinal direction of the composite. This indicates that Si is continuously distributed along the pores of the mesoporous carbon to the inside of the pores. The weight ratio of silicon in each sample was 31.9% (Example 19) and 49.7% (Example 20), respectively (Table 3).

In Example 19 where the amount of silicon introduced was small, it was found that the pores of the composite were not clogged with silicon, and the average pore diameter was reduced from 3 nm to 2 nm (FIG. 16).
On the other hand, in Example 20 where the amount of silicon introduced was large, the pores were blocked with silicon. The remaining pore volume was 0.0265 mL / g, which was about 2.2% of 1.12 mL / g of untreated mesoporous carbon. Since almost the same STEM images were obtained in Example 19 and Example 20 in which the introduction situation of silicon was different, it was presumed that silicon was dispersed in the form of a film on the surface of the pores.

(Examples 21 to 24)
[1. Preparation of sample]
[1.1. Example 21]
Monodispersed spherical mesoporous silica having pores with an average pore size of 2.3 nm was obtained by the method described in Reference 4.
[Reference 4] Yano K, Fukushima Y., J. Mater. Chem., 2003; 13 (10); 2577-81

C ₁₆ TAC: 35.2 g was dissolved in a mixed solvent of purified water: 4126 g and MeOH: 3810 g, and the mixture was stirred at 25 ° C. Further, 26.4 g of TMOS diluted with 34.2 g of 1M NaOH and 30 g of MeOH was added. After stirring for about 8 hours and allowing to stand overnight, filtration and redispersion in purified water were repeated twice. Then, it dried at 45 degreeC and obtained white powder: 17.5g. Further, 2 g of this white powder was calcined in the atmosphere at 550 ° C. for 6 hours to obtain MMSS having an average pore diameter of 2.3 nm.

  Next, in a glove box controlled under an Ar atmosphere, the obtained MMSS having an average pore diameter of 2.3 nm: 0.2 g was put into a glass bottle. Further, CPS was added to the glass bottle for the pore volume and allowed to penetrate into the MMSS. After leaving the glass bottle on the hot plate, the temperature of the hot plate was heated to 400 ° C. and held for 30 minutes. Thereafter, the temperature was lowered to room temperature to obtain a spherical silica / silicon composite.

[1.2. Example 22]
A spherical silica / silicon composite was obtained in the same manner as in Example 4 (introduction of polydihydrosilane liquid) except that MMSS having an average pore diameter of 2.3 nm obtained in Example 21 was used as the porous material.

[1.3. Example 23]
2 g of the white powder (unfired MMSS) obtained in Example 21 was dispersed in a mixed solvent of purified water: 60 mL and EtOH: 60 mL by sonication. To this, docosyltrimethylammonium chloride (C ₂₂ TAC): 5.44 g was added and stirred. The white powder dispersion was placed in an autoclave having an inner cylinder container with a capacity of 200 mL and hydrothermally treated at 80 ° C. for 7 days. After the hydrothermal treatment, the autoclave was cooled and decompressed to take out the product. The product was filtered and redispersed in EtOH twice and washed. Furthermore, after drying at 45 ° C., it was fired in the air at 550 ° C. for 6 hours to obtain MMSS: 0.85 g having an average pore diameter of 3.6 nm.
A spherical silica / silicon composite was obtained in the same manner as in Example 20 (introduction of CPS vapor) except that MMSS having an average pore size of 3.6 nm was used.

[1.4. Example 24]
Using the MMSS having an average pore diameter of 3.6 nm obtained in Example 23 as a porous material, a spherical silica / silicon composite was obtained in the same manner as in Example 4 (introduction of polydihydrosilane liquid).

[2. Test method and results]
In FIG. 17, the SEM image of the sample obtained in Examples 21-24 is shown. FIG. 18 shows the adsorption isotherm of N ₂ at 77 K of these samples and the pore diameter distribution obtained from the adsorption isotherm using the BJH method. 17 and 18 also show the results of MMSS.
Examples 21 to 24 show that even when monodispersed spherical mesoporous silica (MMSS) is used as the porous body, silicon can be introduced into the pores of MMSS according to the present invention.

  In Examples 21 and 22, MMSS having an average pore diameter of 2.3 nm was used, and CPS was introduced in a liquid state or a CPS polymer was introduced in a liquid state. In Examples 23 and 24, MMSS having an average pore diameter of 3.6 nm is used, and CPS is introduced in a vapor state or a CPS polymer is introduced in a liquid state.

Although some silicon deposition was observed outside the MMSS in Example 22, the spherical shape was maintained in any sample, and it was found that there was little silicon deposition outside the MMSS (FIG. 17). Moreover, in any sample, pores having a larger diameter were reduced, and the pore diameter was reduced (FIG. 18). In addition, the tendency is more in Examples 21 and 23 using CPS which is considered to have a relatively large silicon introduction amount than in Examples 22 and 24 using polydihydrosilane which is considered to have a relatively small silicon introduction amount. Was remarkable.
From these results, it was found that even when MMSS is used as a porous body, silicon can be introduced into the pores of MMSS according to the present invention.

(Example 25)
[1. Preparation of sample]
In general, metal oxide nanoparticles aggregate into secondary particles. In the secondary particles, it is considered that the primary particles function as pores and can adsorb silicon compounds such as CPS. Therefore, a titania / silicon composite was obtained in the same manner as in Example 4 (introduction of polydihydrosilane liquid) using Ishihara industrial TiO ₂ nanoparticles: ST01 as a porous material.
In addition, when the pore structure of ST01 was evaluated in advance using an N ₂ adsorption isotherm, the pore diameter was mainly 10 to 50 nm, the average pore diameter was 25 nm, and the pore volume was about 0.57 mL / g. It was found that there were pores.

[2. Test method and results]
FIG. 19 shows the N ₂ adsorption isotherm at 77K of the sample obtained in Example 25 and the pore diameter distribution obtained from the adsorption isotherm using the BJH method. FIG. 19 also shows the result of TiO ₂ .
With the introduction of silicon, the pore size distribution changed slightly in the direction in which the pore size decreased, and the average pore size became 22 nm. From the above results, it was found that silicon can be introduced into the pores of TiO ₂ according to the present invention.

(Example 26)
[1. Preparation of sample]
An alumina / silicon composite was obtained in the same manner as in Example 22 (introduction of polydihydrosilane liquid) except that commercially available γAl ₂ O ₃ nona particles were used as the porous body.
When the pore structure of γAl ₂ O ₃ was evaluated in advance by an N ₂ adsorption isotherm, the pore size was mainly 10 to 50 nm, the average pore size was about 20 nm, and the pore volume was about 0.82 mL / g. Were found to exist.

[2. Test method and results]
FIG. 20 shows the adsorption isotherm of N ₂ at 77 K of the sample obtained in Example 26, and the pore size distribution obtained from the adsorption isotherm using the BJH method. FIG. 20 also shows the result of γAl ₂ O ₃ .
With the introduction of silicon, the capacity of pores of 12 nm or more decreased and the capacity of pores of 10 nm or less increased. The average pore diameter was 10 nm or less. From the above results, it was found that silicon can be introduced into the pores of Al ₂ O ₃ according to the present invention.

(Comparative Example 2)
[1. Preparation of sample]
Attempts were made to introduce silicon into the pores by using the thermal CVD method using silane gas shown below. As the porous body, a spherical carbon porous body having an average pore diameter of 3.8 nm and having radial pores used in Example 13 was used.
That is, 0.2 g of spherical carbon porous material was put into a dent of a quartz glass substrate with a dent, and this was placed on a hot plate in a processing chamber having a capacity of 100 mL. Thereafter, the processing chamber was depressurized to 1 Pa or less, and then the temperature of the hot plate was raised to 400 ° C. Next, silane gas was introduced into the treatment chamber for 30 minutes under the conditions of 30 sccm and 50 Pa, and silicon was introduced into the spherical carbon porous body.

[2. result]
When the weight of the sample after the treatment was measured, it was found that there was almost no change in the weight of the sample accompanying the treatment. Further, when the N ₂ adsorption isotherm of the sample was measured, the adsorption isotherm was almost unchanged before and after the treatment. From these results, it was found that this method cannot introduce silicon into the pores of the spherical carbon porous body.

(Comparative Example 3)
[1. Preparation of sample]
While being held at 400 ° C., silicon was introduced into the spherical carbon porous body in the same manner as in Comparative Example 2 except that plasma was generated 10 times under the condition of 40 W × 1 minute.
[2. result]
Similar to Comparative Example 2, there was almost no change in the weight of the sample accompanying the treatment and no change in the adsorption isotherm. From these results, it was found that this method cannot introduce silicon into the pores of the spherical carbon porous body. Since a silicon film was formed on the surface of the processing chamber, silicon is generated by plasma CVD, but it is considered that silicon does not penetrate into the pores of the spherical carbon porous body.

(Comparative Example 4)
[1. Preparation of sample]
MMSS: 0.15 g having an average pore diameter of 3.6 nm used in Example 23 and Mg: 0.1 g were mixed well. This was placed in an Al ₂ O ₃ crucible and placed in a tubular furnace using a quartz tube having an inner diameter of φ44. While flowing nitrogen at a flow rate of 100 mL / min, the temperature was raised to 650 ° C. and held for 7 hours. Then, it cooled to room temperature. The obtained particles were washed with 2N hydrochloric acid to remove by-products MgO and Mg ₂ Si. Further, unreacted silica was removed with a 5% HF aqueous solution to obtain a porous silicon body.

[2. Test method and results]
The spherical carbon / silicon composite obtained in Example 1: 9.4 mg, Ketjen Black: 2.5 mg, and polytetrafluoroethylene powder: 0.6 mg were kneaded in a mortar to prepare a film. This film was pressed against a SUS mesh to produce a negative electrode for evaluation. Using this electrode as a working electrode, charge / discharge measurement was performed at a current density of 100 mA / g. Lithium metal was used for the counter electrode. As the electrolyte, 1M LiPF ₆ ethylene carbonate: diethyl carbonate (1: 1) v / v% was used.

  Porous silicon obtained in Comparative Example 4: 9.4 mg, Ketjen Black: 2.5 mg, and polytetrafluoroethylene powder: 0.6 mg were kneaded in a mortar to prepare a film. Using this film, the same experiment as in Example 1 was performed.

FIG. 21 shows a change in reversible electric capacity. In the composite obtained in Example 1, the initial reversible electric capacity was 2000 mAh / g or more, and 1000 mAh / g was maintained even after 30 cycles. On the other hand, the porous body obtained in Comparative Example 4 showed a reversible electric capacity of about 1800 mAh / g for the first time. However, the decrease after that was large, and after 15 cycles, it decreased to about 100 mAh / g.
In the porous silicon body of Comparative Example 4, the silicon repeated large volume expansion and contraction with charge / discharge. For this reason, silicon was pulverized and the electric capacity was reduced. On the other hand, in the composite of Example 1, carbon protects silicon, so it is considered that pulverization can be suppressed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

  The composite according to the present invention can be used as a negative electrode material for a Li secondary battery.

Claims (13)

A porous body,
A composite comprising silicon introduced into the pores of the porous body.    2. The composite according to claim 1, wherein the silicon is composed of a film covering an inner wall surface of the pore and / or particles encapsulated in the pore. The composite according to claim 1 or 2, wherein the silicon inclusion rate represented by the following formula (4) is 85% or more.
Inclusion rate (%) = S _SP × 100 / S _S (4)
However, _SSP is the area of the region where both the silicon and the constituent elements of the porous body are detected,
S _S is the area of the region where the silicon is detected. The composite according to any one of claims 1 to 3, wherein a filling rate of the silicon represented by the following formula (5) is 70% or more.
Filling rate (%) = S _SP × 100 / S _P (5)
However, _SSP is the area of the region where both the silicon and the constituent elements of the porous body are detected,
_SP is the area of the region where the constituent elements of the porous body are detected.   The composite according to any one of claims 1 to 4, wherein the porous body is made of carbon or a metal oxide. The metal _{oxide, SiO 2, TiO 2, Ti} 2 O 3, Al 2 O 3, ZrO 2, HfO 2, MgO, CaO, SrO, BaO, CeO 2, Y 2 O 3, Sc 2 O 3 and, The composite according to claim 5, comprising at least one oxide selected from the group consisting of Li ₂ O. The porous body is made of carbon,
The composite according to any one of claims 1 to 5, wherein a weight ratio of the silicon represented by the formula (3) is 5% or more and 80% or less.
Weight ratio (%) = W _t × 100 / W _c (3)
Where W _t is the total weight of the silicon contained in the composite,
W _c is the weight of the complex. The said porous body is a composite_body | complex of any one of Claim 1-7 whose pore diameter dispersion degree represented by following (2) Formula is 1/2 or less.
Pore diameter dispersion = Δd _p / d _p (2)
Where Δd _p is the full width at half maximum of the pore size distribution curve,
d _p is the average pore diameter.   The composite according to any one of claims 1 to 8, wherein the porous body has an average pore diameter of 1 nm or more and 100 nm or less.   The composite according to any one of claims 1 to 9, wherein the porous body is a spherical particle.   The composite according to claim 10, wherein the spherical particles have a monodispersity of 10% or less. A preparation step of preparing a porous body;
Introducing a vapor of a silicon compound that is liquid at room temperature, or introducing a liquid or solution of the silicon compound into the pores of the porous body;
The manufacturing method of the composite_body | complex provided with the siliconization process which converts the said silicon compound into a silicon | silicone in the said pore after the said introduction process or simultaneously with the said introduction process.   The method for producing a composite according to claim 12, wherein the silicon compound is at least one compound selected from silicon hydride compounds having one or more cyclic structures.

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