JP2021172544A - Composite material, method for producing the same and all-solid-state lithium ion secondary battery - Google Patents

Abstract

To provide a composite material that contains carbon material and metal oxide and that is used as a component of an electrode layer (a positive electrode layer and/or a negative electrode layer) of an all-solid-state lithium ion secondary battery and can attain high capacity and high output properties even when the positive electrode layer, a solid electrolyte layer and the negative electrode layer are laminated under low pressure.SOLUTION: A composite material includes a gas-phase-method carbon fiber, and a metal oxide layer that covers the surface of the gas-phase-method carbon fiber in a sea-island form. The coverage of the gas-phase-method carbon fiber with the metal oxide layer is 20% or more and 80% or less.SELECTED DRAWING: None

Description

The present invention relates to a composite material, a method for producing the same, an electrode layer and an electrode for an all-solid-state lithium ion secondary battery including the composite material, and an all-solid-state lithium ion secondary battery.

In recent years, lithium ion secondary batteries have become widespread as a power source for electronic devices such as laptop computers and mobile phones, and transportation devices such as automobiles. There is an increasing demand for these devices to be smaller, lighter, and thinner. In order to meet these demands, a small, lightweight and high-capacity secondary battery is required.

In a general lithium ion secondary battery, a carbon material such as a compound containing lithium as a positive electrode active material, graphite as a negative electrode active material, and heat-treated coke is used. Further, between the positive electrode and the negative electrode, an electrolytic solution obtained by dissolving a lithium salt such _{as LiPF 6} or LiBF _{4 as an electrolyte in an aprotonic solvent having penetrating power such as propylene carbonate or ethylene carbonate, or an electrolytic solution thereof.} It is provided with an electrolyte layer made of a polymer gel impregnated with. These configurations are packaged and protected by a battery case packaging material.

In an all-solid-state lithium-ion secondary battery, there is a solid electrolyte layer between the positive electrode layer and the negative electrode layer. That is, the electrolyte of the above-mentioned general lithium ion secondary battery is solidified. As the solid electrolyte, sulfides such as _{Li 2} S and P ₂ S _{5 are typically used.} As the negative electrode active material for the negative electrode, a carbon material such as graphite is typically used.

Here, the electrode layer of the all-solid-state lithium ion battery is formed by mixing the electrode active material and the solid electrolyte. However, carbonic materials such as those used for negative electrode active materials, conductive auxiliaries, and carbon-coated positive electrode active materials have low surface affinity with solid electrolytes, and therefore, when these are simply mixed, they are carbonaceous. The problem is that the material and the solid electrolyte are not uniformly dispersed, and the capacitance and rate characteristics are lowered.

Japanese Unexamined Patent Publication No. 2017-54614 JP-A-2018-88425 Japanese Patent Application Laid-Open No. 2011-528257 Japanese Unexamined Patent Publication No. 2006-0083462

The present inventors have the idea of coating the surface of the carbonic material with a metal oxide having an affinity for the surface of the solid electrolyte in order to improve the dispersibility between the carbonic material and the solid electrolyte as described above. Got

As an example in which the surface of a carbon material is coated with a metal oxide, Patent Document 1 discloses that the surface of a negative electrode active material such as a carbon material is provided with a particulate coating portion composed of an aluminum oxide. .. Patent Document 2 discloses a non-aqueous electrolyte secondary battery including a negative electrode including a titanium-containing oxide layer that covers at least a part of the surface of graphite material particles. Patent Document 3 discloses a composite material containing carbon fibers and composite oxide particles. Further, Patent Document 4 discloses a hydrophilic vapor-grown carbon fiber in which metal oxide particles are attached to the vapor-grown carbon fiber.

However, in general, metal oxides have high surface-to-surface affinity with solid electrolytes having excellent ionic conductivity, but have poor electron conductivity. Therefore, it is sufficient to simply coat a carbonaceous material with metal oxides. No. Although both Patent Documents 1 and 2 disclose an active material in which the surface of a carbonaceous material is coated with a metal oxide, no studies have been made from such a viewpoint. In Patent Documents 3 and 4, since the metal oxide is in the shape of particles, when mixed with the solid electrolyte, the contact area between the metal oxide particles and the solid electrolyte particles is small, and the ion conduction path may be relatively small. There is.

In some cases, a method of improving the capacitance and rate characteristics by strongly pressurizing the electrode layer to improve the adhesion is used, but in that case, there is a problem that the cycle characteristics deteriorate due to cracking of the active material. do.

An object of the present invention is that when used as a component of an electrode layer (either one or both of a positive electrode layer and a negative electrode layer) of an all-solid-state lithium ion secondary battery, the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are low. It is an object of the present invention to provide a composite material containing a carbon material and a metal oxide, which can obtain high capacity and high output characteristics even when laminated by pressurization.

The present inventors have found that the above problems can be solved by coating the surface of the vapor phase carbon fiber with a metal oxide layer in a sea-island shape, and have completed the present invention.
[1] A vapor phase carbon fiber and a metal oxide layer that coats the surface of the vapor phase carbon fiber in a sea-island shape are included, and the coverage of the vapor phase carbon fiber by the metal oxide layer is 20%. A composite material that is 80% or more and 80% or less.
[2] The composite material according to the above [1], wherein the vapor phase method carbon fibers are graphitized.
[3] The composite material according to any one of the above [1] and [2], wherein the metal oxide layer has an average thickness of 10 nm or more.
[4] The metal oxides constituting the metal oxide layer are contained in an amount of 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the vapor phase carbon fiber. 3] The composite material according to any one of the items.
[5] The metal oxides constituting the metal oxide layer are Li, Na, K, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, The composite material according to any one of [1] to [4] above, which comprises an oxide of a metal selected from Pt, Ru, Rh, Pd, Ag, Al, Ga, In, Tl, Sn and Pb.
[6] Any one of the above [1] to [5], wherein the metal oxide constituting the metal oxide layer contains at least one metal oxide selected from the group consisting of lithium titanate and lithium niobate. The composite material described in the section.
[7] The BET specific surface area is 20.0 m ² _{/ g or less, and the average plane spacing d 002} of the (002) plane by X-ray diffraction measurement is 0.3354 nm or more and less than 0.3400 nm. The composite material according to any one of [6].
[8] The composite material according to any one of [1] to [7] above, wherein the average fiber diameter D _{fa is 100 nm or more and 300 nm or less.}
[9] The composite material according to any one of [1] to [8] above, further comprising at least one selected from the group consisting of a particulate conductive auxiliary agent, a fibrous conductive auxiliary agent, and solid electrolyte particles.
[10] An electrode layer for an all-solid-state lithium ion secondary battery containing the composite material, active material, and solid electrolyte according to any one of the above [1] to [9].
[11] The electrode for an all-solid-state lithium ion secondary battery including the electrode layer for the all-solid-state lithium ion secondary battery and the current collector according to the above [10].
[12] An all-solid-type lithium ion secondary battery having a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode and the negative electrode. An all-solid-state lithium-ion secondary battery in which one or both of the negative electrode and the positive electrode contains the composite material according to any one of [1] to [9].
[13] The method for producing a composite material according to any one of the above [1] to [9].
A step of preparing a precursor solution containing at least one metal oxide precursor selected from a metal alkoxide and a metal complex and a solvent.
A composite including a step of spraying the precursor solution on the gas phase carbon fiber in a fluid state and a step of heat-treating the vapor phase carbon fiber to which the metal oxide precursor is attached to form a metal oxide layer. Material manufacturing method.
[14] The method for producing a composite material according to any one of the above [1] to [9].
A step of preparing a precursor solution containing at least one metal oxide precursor selected from a metal alkoxide and a metal complex and a solvent.
A method for producing a composite material, which comprises a step of spraying the precursor solution onto the fluidized vapor phase carbon fibers and a step of forming a metal oxide layer from the metal oxide precursor by a sol-gel reaction.
[15] The method for producing a composite material according to the above [13] or [14], wherein the precursor solution further contains a lithium compound.

By using the composite material in one embodiment of the present invention as one component of the electrode layer (either one or both of the positive electrode layer and the negative electrode layer) of the all-solid-state lithium ion secondary battery, the active material in the electrode layer and The dispersibility of both the solid electrolytes is improved, and high capacity and high output characteristics can be obtained even when the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are laminated by low pressure.

It is the schematic sectional drawing which showed an example of the structure of the all-solid-state lithium ion battery 1 of this invention. It is a schematic cross-sectional view which showed an example of the structure of the composite material of this invention.

Hereinafter, embodiments of the present invention will be described.
In the following description, "50% particle size in the volume-based cumulative particle size distribution" and "D _pV50 " are particle sizes that are 50% in the volume-based cumulative particle size distribution obtained by the laser diffraction / scattering method. Further, in the "average fiber diameter D _fa ", the diameters of 10 points in one fibrous composite material randomly selected from the SEM image are measured by image recognition software, and the arithmetic average value is measured as the one fibrous composite material. The fiber diameter of the composite material is used, and the fiber diameter is measured for a total of 100 fibrous composite materials, and the obtained 100 fiber diameters are calculated and averaged.

[1] Composite Material The composite material according to the embodiment of the present invention (hereinafter, also referred to as "composite material (I)") covers the vapor phase carbon fiber and the surface of the vapor phase carbon fiber in a sea-island shape. The coverage of the vapor phase carbon fiber by the metal oxide layer is 20% or more and 80% or less.

FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the composite material (I). Hereinafter, the composite material (I) will be described with reference to FIG. 2 as necessary, but the reference numerals attached to the respective components may be omitted.
The composite material (I) 2 includes a vapor phase carbon fiber 21 and a metal oxide layer 22 that coats the surface of the vapor phase carbon fiber 21 in a sea-island shape.

The surface of the composite material (I) has both an exposed portion of the vapor phase carbon fiber 21 and a portion of the metal oxide layer 22 in a specific proportion. That is, both the vapor-phase carbon fiber 21 having excellent electron conductivity and the metal oxide layer 22 having excellent ionic conductivity form the surface of the composite material (I) in a specific ratio. Here, when an active material having a carbonaceous surface such as graphite or a carbon-coated positive electrode active material is mixed with the solid electrolyte and the composite material (I), the carbonaceous surface is changed due to the affinity between the respective surfaces. The active material to have is often arranged on the surface of the vapor phase carbon fiber 21 of the composite material, and the solid electrolyte is often arranged on the surface of the metal oxide layer 22 of the composite material. As a result, a good dispersion state is achieved for all of the composite material, the active material and the solid electrolyte. As a result, in the electrode layer, which is a mixture of the active material, the solid electrolyte, the composite material (I), and the conductive auxiliary agent and the binder as optional components, the moving path of the lithium ions uniformly dispersed and the electrons uniformly dispersed. It is considered that a conduction path can be formed. Therefore, in an all-solid-state lithium ion secondary battery using such an electrode layer, high capacity and good rate characteristics can be obtained.

The metal oxide layer 22 is a layer that covers the surface of the vapor phase carbon fiber 21. The metal oxide layer 22 exhibits a sea-island structure scattered in an island shape on the surface of the vapor phase carbon fiber 21. The coverage of the metal oxide layer 22 is 20% or more, preferably 25% or more, and more preferably 30% or more. By setting the coverage to 20% or more, the ionic conduction path near the surface of the composite material (I) can be increased. The coverage is 80% or less, preferably 70% or less, and more preferably 65% or less. By setting the coverage to 80% or less, it is possible to maintain a sufficiently large number of electron conduction paths near the surface of the composite material (I).

The fact that the metal oxide layer 22 covers the surface of the vapor phase carbon fiber 21 in an island shape can be confirmed by mapping such as EDS, AES, and Raman spectroscopy.

The coverage can be adjusted, for example, with respect to the vapor phase carbon fiber 21 according to production conditions such as the amount of metal oxide precursor added, the rate of addition, and the atmospheric temperature, which will be described later. In addition, the coverage can be measured by binarizing a scanning electron microscope (SEM) image or a composition analysis image.

The average thickness of the metal oxide layer 22 of the composite material (I) is preferably 10 nm or more, more preferably 12 nm or more, still more preferably 15 nm or more. Chemical stability and mechanical strength can be ensured by setting the average thickness to 10 nm or more. The average thickness of the metal oxide layer 22 of the composite material (I) is preferably 75 nm or less, more preferably 50 nm or less, still more preferably 20 nm or less. By setting the average thickness to 75 nm or less, it is possible to prevent the size of the composite material from becoming larger than necessary, and the lithium ion conductivity and electron conductivity of the all-solid-state lithium ion secondary battery using the composite material (I) can be prevented. The sex can be balanced and the cycle characteristics can be improved. The average thickness of the metal oxide layer 22 can be measured by the method described in Examples.

In the composite material (I), the content of the metal oxide layer with respect to 100 parts by mass of the vapor phase carbon fiber is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, still more preferably 0.5 part by mass. It is more than a mass part. By setting the content of the metal oxide layer to 0.1 parts by mass or more, a region having a high affinity with the solid electrolyte can be sufficiently secured on the composite material (I), so that ionic conduction between these can be sufficiently secured. It is done smoothly. The content of the metal oxide layer is preferably 10 parts by mass or less, more preferably 5.5 parts by mass or less, and further preferably 3.0 parts by mass or less. By setting the content of the metal oxide layer to 10 parts by mass or less, the vapor-phase carbon fibers in the composite material (I) are sufficiently exposed, and the portion is used as a contact point between the composite materials or with the composite material. Electron conduction with the substance is performed smoothly. For electron conduction, for example, the measurement of volume resistivity with respect to the electrode layer by a four-probe method, etc., and for ion conduction, for example, the electrode layer is sandwiched between blocking electrodes such as platinum. It can be clarified from the AC measurement of the electrochemical cell. In each case, it can be confirmed in the form of improvement in the apparent electron conductivity and the apparent ionic conductivity of the electrode layer by comparing with the measured values when these composite materials are not used. By smoothing electron conduction and ion conduction, battery characteristics such as DC resistance and rate characteristics of the cell as a whole are also improved.

The BET specific surface area of the composite material (I) is preferably 3.0 m ² / g or more, more preferably 4.0 m ² / g or more, and further preferably 5.0 m ² / g or more. When the BET specific surface area is 3.0 m ² / g or more, the reaction area for lithium insertion / desorption in the composite material (I) is sufficiently present, so that the rate characteristics are improved. Further, BET specific surface area of the composite material (I) is preferably 20.0 m ² / g or less, more preferably 18.0m ² / g or less, more preferably 15.0 m ² / g or less, particularly preferably 10. It is 0 m ² / g or less. When the BET specific surface area is 20.0 m ² / g or less, the area of the reaction (side reaction) between the composite material (I) and the solid electrolyte is kept small, so that the initial Coulomb efficiency is high. The BET specific surface area can be measured by the method described in Examples.

_{The average plane spacing d 002} of the (002) plane derived from the vapor phase carbon fiber by X-ray diffraction measurement of the composite material (I) is preferably 0.3354 nm or more. 0.3354 nm is _{the theoretical value of d 002} of the graphite crystal and is also the lower limit value. Further, d ₀₀₂ is more preferably 0.3356 nm or more from the viewpoint of less expansion and contraction and excellent cycle characteristics when the graphite crystal structure is not overdeveloped. Further, d ₀₀₂ has sufficient crystallinity, and therefore, from the viewpoint of obtaining good electron conductivity and suppressing side reactions, it is preferably less than 0.3400 nm, more preferably 0.3390 nm or less, and further. It is preferably 0.3380 nm or less. d ₀₀₂ can be measured using the powder X-ray diffraction (XRD) method. Specific measurement methods are described in the section of Examples.

_{The average fiber diameter D fa} of the composite material (I) is preferably 100 nm or more, more preferably 110 nm or more, still more preferably 120 nm or more. By _{setting the D fa} to 100 nm or more, the handleability of the composite material (I) is improved, and the composite material (I) is mixed with a solid electrolyte as a component of the electrode layer of the all-solid-state lithium ion secondary battery. When used, the dispersibility of both the active material and the solid electrolyte in the electrode layer is improved, and the capacity and rate characteristics of the battery are improved. The D _fa is preferably 300 nm or less, more preferably 270 nm or less, and further preferably 250 nm or less. By _{setting the D fa} to 300 nm or less, the state where the specific surface area of the composite material (I) is large can be maintained, and when the composite material (I) is used as a component of the electrode layer of the all-solid-state lithium ion secondary battery. , The volumetric energy density of the battery is improved.

[2] Gas phase carbon fiber The vapor phase carbon fiber contained in the composite material (I) is not particularly limited, and the vapor phase carbon fiber produced by a known method or a commercially available vapor phase carbon fiber (for example, Showa Denko) The "VGCF (registered trademark)" series) manufactured by Co., Ltd. can be used.

The vapor-phase carbon fiber can be produced, for example, by using an organic compound as a raw material, introducing an organic transition metal compound as a catalyst into a high-temperature reaction furnace together with a carrier gas, producing the carbon fiber, and then heat-treating the carbon fiber (Japan). Japanese Patent Application Laid-Open No. 60-54998, Japanese Patent No. 2778434, etc.). Its fiber diameter is 2 to 1000 nm, preferably 10 to 500 nm, and its aspect ratio is preferably 10 to 15000. Further, as a structure peculiar to the vapor phase carbon fiber, there is a structure in which hexagonal net planes of graphite are laminated concentrically, and a hollow portion along the longitudinal direction exists inside the fiber.

Examples of the organic compound used as a raw material for the vapor-phase carbon fiber include gases such as toluene, benzene, naphthalene, ethylene, acetylene, ethane, methane, natural gas, and carbon monoxide, and mixtures thereof. Of these, aromatic hydrocarbons such as toluene and benzene are preferable.

The organic transition metal compound contains a transition metal that serves as a catalyst. Examples of the transition metal include metals of Group IVa, Va, VIa, VIIa, and VIII of the Periodic Table. As the organic transition metal compound, compounds such as ferrocene and nickelocene are preferable.

Examples of the vapor phase carbon fiber include untreated carbon fibers, calcined carbon fibers, and graphitized carbon fibers, and among these, graphitized carbon fibers are preferably used. If the graphitized vapor phase carbon fiber is used, the metal oxide layer can be satisfactorily formed on the surface of the vapor phase carbon fiber in a sea-island shape.

Examples of the method for graphitizing carbon fibers by the vapor phase method include a method of heat-treating the carbon fibers under the condition of 2800 ° C. in an argon atmosphere. The graphitized vapor phase carbon fiber has an XRD d ₀₀₂ of less than 0.3400 nm.

[3] Metal Oxide Layer The metal oxide constituting the metal oxide layer contained in the composite material (I) is not particularly limited, but Li, Na, K, Mg, Ca, Ti, V, Cr, Mn, It preferably contains oxides of metals selected from Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, Pt, Ru, Rh, Pd, Ag, Al, Ga, In, Tl, Sn and Pb. At least one selected from the group of lithium titanate (Li ₂ TiO ₃ , LiTIO ₂ , Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O _4, etc.), lithium niobate (LiNbO ₃ ) and titanium oxide (amorphous). It is more preferable to include it. This is because lithium titanate and lithium niobate are excellent in lithium ion conductivity and have a high surface affinity with a solid electrolyte. Lithium titanate is most preferred.

[4] Other Components The composite material (I) is composed of components other than the above-mentioned vapor-phase carbon fiber and metal oxide layer, for example, a particulate conductive auxiliary agent, a fibrous conductive auxiliary agent, and solid electrolyte particles. It may further comprise at least one selected from the group.

The particulate conductive auxiliary agent, the fibrous conductive auxiliary agent, and the solid electrolyte particles may have a structure adhered to the surface of the metal oxide layer, or have a structure in which a part or all of the metal oxide layer is embedded. You may.

The content of other components is preferably 0.1 part by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the vapor phase carbon fiber.

Examples of the particulate conductive auxiliary agent include carbon black, acetylene black, and Ketjen black. When the composite material (I) contains the particulate conductive auxiliary agent, the electron conduction path on the surface of the composite material (I) is increased.
Examples of the fibrous conductive auxiliary agent include carbon nanotubes. When the composite material (I) contains a fibrous conductive auxiliary agent, the electron conduction path on the surface of the composite material (I) is increased.
Examples of the solid electrolyte particles include particulate sulfide-based solid electrolytes and particulate oxide-based solid electrolytes. The inclusion of the solid electrolyte particles in the composite material (I) improves the dispersibility of the solid electrolyte when preparing the electrode layer.
The composite material (I) containing other components can be obtained, for example, by mixing the other components and the composite material (I) with a planetary ball mill.

_{The 50% particle size D pV50} in the volume-based cumulative particle size distribution of the solid electrolyte particles is preferably 10 nm or more and 1 μm or less. D _pV50 can be measured by using a laser diffraction type particle size distribution measuring device. Specifically, it can be measured by the method described in Examples.

[5] Content of metal oxide layer The mass of vapor-phase carbon fibers contained in the composite material is measured using a carbon / sulfur analyzer, and the content of the metal oxide is determined by subtracting it from the mass of the composite material. be able to. If other components are attached to the composite material, the content of each component can be separately determined by quantitative analysis of metal elements by inductively coupled plasma emission spectrometry (ICP-AES) or the like. ..
When the composite material (I) contains a solid electrolyte in which the metal oxide layer and the constituent elements are partially the same, for example, TEM-EELS or the like is used to clarify the composition of the metal oxide layer and the composition of the solid electrolyte, respectively. The content of each element can be determined from the content of each element obtained by quantitative analysis.

[6] Method for Producing Composite Material (I) Hereinafter, embodiments of the method for producing the composite material (I) of the present invention will be exemplified, but the method for producing the composite material (I) of the present invention is not limited to the following.

In the method for producing the composite material (I) according to the embodiment of the present invention, a precursor solution containing at least one metal oxide precursor selected from a metal alkoxide and a metal complex (including a chelate complex) and a solvent is prepared. The step of spraying the precursor solution onto the fluidized carbon material, and the step of heat-treating the carbon material to which the metal oxide precursor is attached to form a metal oxide layer are included.

The method for producing the composite material (I) according to another embodiment of the present invention is a precursor solution containing at least one metal oxide precursor selected from a metal alkoxide and a metal complex (including a chelate complex) and a solvent. The steps include a step of spraying the precursor solution onto the fluidized carbonaceous material, and a step of forming a metal oxide layer from the metal oxide precursor by a sol-gel reaction.

The metal oxide precursor is at least one selected from metal alkoxides and metal complexes (including chelate complexes), and those that are stably dissolved in a solvent are preferable. Specific examples thereof include tetraisopropyl orthotitamate, niobium (V) ethoxide, vanadium (V) triethoxydo oxide, aluminum triethoxydo, and zirconium (IV) ethoxide.

The solvent is selected from water or an organic solvent, and is not particularly limited as long as it can dissolve the metal oxide precursor, but an organic solvent having a large polarity such as methanol, ethanol, isopropyl alcohol, butanol is preferable. The organic solvent preferably has a boiling point of 200 ° C. or lower.

The precursor solution preferably further contains a lithium compound. In this case, the metal oxide becomes a metal oxide containing lithium, and the lithium ion conductivity is increased. Examples of the lithium compound include methoxylithium and ethoxylithium.

The concentration of the metal oxide precursor in the precursor solution is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, from the viewpoint of facilitating the formation of a sea-island structure. Further, if the concentration of the metal oxide precursor is too high, the thickness of the metal oxide precursor layer is unlikely to be 75 nm or less, so that it is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferable. Is 35% by mass or less.

Gas phase method The method of putting the carbon fibers into a fluidized state is not particularly limited, but a method using a rolling fluidized bed or a swirling fluidized bed can be mentioned, and a method using a rolling fluidized bed is preferable. Examples of the rolling fluidized bed device include the MP series manufactured by Paulec.

When a rolling fluidized bed is used, the supply air temperature is preferably operated at the boiling point of the organic solvent + 5 to 20 ° C. or higher. Within this range, a metal oxide precursor layer having a thickness of 75 nm or less can be easily formed.

When a rolling fluidized bed is used, it is preferably performed in a low humidity atmosphere. Examples of the low humidity atmosphere include a nitrogen gas atmosphere, an argon gas atmosphere, and an air atmosphere having a humidity of 25% or less.

The amount of air supply to the rolling fluidized bed is not limited, but conditions under which the vapor-phase carbon fibers completely flow are preferable.

The method of spraying the precursor solution onto the vapor phase carbon fiber is not particularly limited, and examples thereof include a method using a tube pump, a compressor, and a spray nozzle.

A metal oxide layer can be formed by heat-treating the vapor-phase carbon fibers after spraying the precursor solution. Further, when the metal oxide layer is formed by a sol-gel reaction or the like, the metal oxide layer can be formed without heat treatment.
The heat treatment conditions are not particularly limited, but the heat treatment temperature is preferably 200 ° C. or higher and 500 ° C. or lower. The rate of temperature rise is preferably 10 ° C./h or more and 200 ° C./h or less. The maximum temperature holding time is preferably 1 h or more and 5 hours or less. The temperature lowering rate is preferably 10 ° C./h or more and 300 ° C./h or less. When the metal oxide layer contains a sulfide-based solid electrolyte, it is preferably carried out in a nitrogen gas atmosphere or an argon gas atmosphere.
The conditions of the sol-gel reaction are not particularly limited as long as an aqueous metal alkoxide solution is used and hydrolysis occurs when the aqueous solution is sprayed to generate oxide particles.

When a structure in which a part or all of the above-mentioned particulate conductive auxiliary agent, fibrous conductive auxiliary agent, solid electrolyte particles, etc. is embedded in the metal oxide layer, these components are contained in the precursor solution. It can be produced by spraying on vapor phase carbon fibers in the next step. The blending amount of these components is preferably 0.1 part by mass or more and 10.0 parts by mass or less when the vapor phase carbon fiber used is 100 parts by mass.

In order to improve the dispersibility of these components in the precursor solution, a dispersant such as a surfactant may be blended in the precursor solution.

When the structure is such that the particulate conductive auxiliary agent, the fibrous conductive auxiliary agent, the solid electrolyte particles, etc. are attached to the metal oxide layer, the above components are attached to the surface of the composite material after the metal oxide layer is formed. It can also be manufactured by. Examples of the method of adhering include a method using a stirring and mixing granulator, a spray dry, and the like. Examples of the stirring and mixing granulator include the VG series manufactured by Paulec. The amount of the vaporized carbon fiber in the composite material is preferably 0.1 part by mass or more and 10.0 part by mass or less when 100 parts by mass is taken.

Further, a method of incorporating a particulate conductive auxiliary agent, a fibrous conductive auxiliary agent, a solid electrolyte particle or the like in the precursor solution and a method of adhering the particles may be used in combination, and a method of forming a solid electrolyte layer on the surface is also used in combination. You can also do it. Even when these are used in combination, the total amount of the particulate conductive auxiliary agent, the fibrous conductive auxiliary agent, the solid electrolyte particles, the solid electrolyte layer, etc. is 0.1 part by mass or more when the vapor phase method carbon fiber is 100 parts by mass. It is preferably 10.0 parts by mass or less.

[7] All-solid-state lithium-ion secondary battery The all-solid-state lithium-ion secondary battery according to an embodiment of the present invention (hereinafter, also simply referred to as “battery (II)”) is a positive electrode containing a positive electrode active material. And a negative electrode containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode and the negative electrode, and either one or both of the negative electrode and the positive electrode contains a composite material (I). ..

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the battery (II). Hereinafter, the battery (II) will be described with reference to FIG. 1 as necessary, but the reference numerals attached to the respective components may be omitted.
As shown in FIG. 1, the all-solid-state lithium ion secondary battery (II) 1 includes a positive electrode layer 112, a solid electrolyte layer 12, and a negative electrode layer 132.

When the electrode layer (either one or both of the positive electrode layer and the negative electrode layer) is formed using the composite material (I), the surface affinity between the composite material (I) and the solid electrolyte is high, so that the positive electrode layer 112 When the battery (II) is manufactured by laminating the solid electrolyte layer 12 and the negative electrode layer 132, the battery (II) can be manufactured at a low pressure of ^{1 MPa (10 kgf / cm 2) or less.}

The positive electrode 11 has a positive electrode current collector 111 and a positive electrode layer 112. A positive electrode lead 111a for exchanging electrons with an external circuit is connected to the positive electrode current collector 111. The positive electrode current collector 111 is preferably a metal foil, and the metal foil is preferably an aluminum foil.

The positive electrode layer 112 contains a positive electrode active material and a solid electrolyte, and may further contain a composite material (I), a conductive additive, a binder, and the like. Examples of the positive electrode active material include layered compounds such _{as LiCoO 2 , LiMnO 2} , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , spinel-type compounds such as _{LiMn 2} O _{4 , LiFePO 4} , and LiFePO 4. LiMnPO _4, LiNiPO _4, LiCuPO olivine type compound such as _4, may be used sulfides such as Li ₂ S. Further, these positive electrode active materials may be coated with LTO (Lithium Tin Oxide), carbon or the like.

When the positive electrode layer 112 contains the composite material (I), the content of the composite material (I) in the positive electrode layer 112 is preferably 0.1 part by mass or more, more preferably 1 with respect to 100 parts by mass of the positive electrode active material. It is by mass or more, more preferably 2 parts by mass or more. When the content of the composite material (I) is 0.1 parts by mass or more, the positive electrode active material and the solid electrolyte can be uniformly distributed in the positive electrode layer 112. The content of the composite material (I) in the positive electrode layer 112 is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less. When the content of the composite material (I) is 50 parts by mass or less, the required amount of the positive electrode active material can be filled in the limited space of the battery case.

As the solid electrolyte contained in the positive electrode layer 112, the materials listed in the solid electrolyte layer 12 described later can be used, but a material different from the material contained in the solid electrolyte layer 12 may be used. The content of the solid electrolyte in the positive electrode layer 112 is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and further preferably 80 parts by mass or more with respect to 100 parts by mass of the positive electrode active material. The content of the solid electrolyte in the positive electrode layer 112 is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and further preferably 125 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.

As the conductive auxiliary agent that may be contained in the positive electrode layer 112, a particulate carbonaceous conductive auxiliary agent or a fibrous carbonaceous conductive auxiliary agent is preferable. Particley carbonaceous conductive aids include Denka Black (registered trademark) (manufactured by Denki Kagaku Kogyo Co., Ltd.), Ketjen Black (manufactured by Lion Co., Ltd.), graphite fine powder SFG series (manufactured by Timcal), graphene and the like. Carbon can be used. As the fibrous carbonaceous conductive auxiliary agent, vapor phase carbon fibers (VGCF (registered trademark), VGCF (registered trademark) -H (manufactured by Showa Denko KK)), carbon nanotubes, carbon nanohorns and the like can be used. .. The vapor phase carbon fiber "VGCF (registered trademark) -H" (manufactured by Showa Denko KK) is most preferable because of its excellent cycle characteristics. The content of the conductive auxiliary agent in the positive electrode layer 112 is preferably 0 parts by mass or more, and more preferably 1 part by mass or more with respect to 100 parts by mass of the positive electrode active material. The content of the conductive auxiliary agent in the positive electrode mixture layer 112 is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the positive electrode active material.

Examples of the binder that may be contained in the positive electrode layer 112 include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, polyvinyl acetate, polymethacrylate, polyacrylate, polyacrylonitrile, polyvinyl alcohol, styrene-butadiene rubber, and carboxymethyl cellulose. And so on.

In the positive electrode layer 112, the content of the binder with respect to 100 parts by mass of the positive electrode active material is preferably 0 parts by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 7 parts by mass or less.

The solid electrolyte layer 12 is a phase (ion conduction phase) that is interposed between the positive electrode layer 112 and the negative electrode layer 132, and electricity is mainly carried by lithium ions between the positive electrode layer 112 and the negative electrode layer 132. The solid electrolyte layer 12 preferably contains at least one selected from the group consisting of a sulfide solid electrolyte and an oxide solid electrolyte, and more preferably contains a sulfide solid electrolyte.

Examples of the sulfide solid electrolyte include sulfide glass, sulfide glass ceramics, and Thio-LISION type sulfide. More specifically, for _{example, Li 2 S-P 2 S} 5, Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 S 5 -LiBr, _{Li 2 S-P 2 S 5} -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2, Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li ₂ S-SiS _2- LiCl, Li ₂ S-SiS _2- B ₂ S _3- LiI, Li ₂ S-SiS ₂ -P ₂ S _5- LiI, Li _{2 SB 2} S ₃ , Li ₂ SP ₂ S _{5- Z m} S _n (in the formula, m and n represent positive numbers, Z represents any of Ge, Zn, Ga), Li ₂ S-GeS ₂ , Li ₂ S- SiS _{2 -Li 3} PO ₄ , Li ₂ S-SiS _{2 -Li x} MO _y (in the formula, x, y are positive numbers, M is P, Si, Ge, B, Al, Ga, In. _{represents.), Li 10 GeP 2 S} 12, Li 3.25 Ge 0.25 P 0.75 S 4, 30Li 2 S · 26B 2 S 3 · 44LiI, 63Li 2 S · 36SiS 2 · 1Li 3 PO 4, 57Li 2 S · 38SiS 2 · 5Li ₄ SiO ₄ , 70Li ₂ S ・ 30P ₂ S ₅ , 50LiS ₂・ 50GeS ₂ , Li ₇ P ₃ S ₁₁ , Li _3.25 P _0.95 S ₄ , Li ₃ PS ₄ , Li ₂ S ・ P ₂ S ₃・ P ₂ S ₅ etc. can be mentioned. The sulfide solid electrolyte material may be amorphous, crystalline, or glass-ceramic.

Examples of the oxide solid electrolyte include perovskite-type, garnet-type, and LISION-type oxides. More specifically, for example, La _0.51 Li _0.34 TiO _2.94 , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , 50Li ₄ SiO ₄・ 50Li ₃ BO ₃ , Li _2.9 PO _3.3 Examples thereof include N _0.46 (LIPON), Li _3.6 Si _0.6 P _0.4 O ₄ , Li _1.07 Al _0.69 Ti _1.46 (PO ₄ ) ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ . The oxide solid electrolyte material may be amorphous, crystalline, or glass-ceramic.

The negative electrode 13 has a negative electrode current collector 131 and a negative electrode layer 132. The negative electrode current collector 131 is connected to an external circuit and a negative electrode lead 131a for exchanging electrons. The negative electrode current collector 131 is preferably a metal foil, and the metal foil is preferably a stainless foil, a copper foil, or an aluminum foil. The surface of the current collector may be coated with carbon or the like.

The negative electrode layer 132 contains a negative electrode active material and a solid electrolyte, and may further contain a composite material (I), a binder, a conductive auxiliary agent, and the like. The negative electrode active material is not particularly limited, and examples thereof include carbonic materials such as graphite which are generally used as the negative electrode active material of an all-solid-state lithium ion battery. As the carbonaceous material, for example, spherical natural graphite or artificial graphite is preferable.

As the solid electrolyte contained in the negative electrode layer 132, the materials listed in the solid electrolyte layer 12 can be used, but they are different from the solid electrolyte contained in the solid electrolyte layer 12 or the solid electrolyte contained in the positive electrode layer 112. Materials may be used. The content of the solid electrolyte in the negative electrode layer 132 is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and further preferably 80 parts by mass or more with respect to 100 parts by mass of the negative electrode active material. The content of the solid electrolyte in the negative electrode mixture layer 132 is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and further preferably 125 parts by mass or less with respect to 100 parts by mass of the negative electrode active material.

As the conductive auxiliary agent that may be contained in the negative electrode layer 132, the conductive auxiliary agent mentioned in the description of the positive electrode layer 112 can be used, but a material different from the conductive auxiliary agent contained in the positive electrode layer 112 is used. May be good. The content of the conductive auxiliary agent in the negative electrode layer 132 is preferably 0 parts by mass or more, and more preferably 1 part by mass or more with respect to 100 parts by mass of the negative electrode active material. The content of the conductive auxiliary agent in the negative electrode layer 132 is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the negative electrode active material.

As the binder, for example, the materials mentioned in the description of the positive electrode layer 112 can be used, but the binder is not limited thereto. In the negative electrode layer 132, the content of the binder with respect to 100 parts by mass of the negative electrode active material is preferably 0 parts by mass or more and 10 parts by mass or less, and more preferably 0 parts by mass or more and 5 parts by mass or less.

[8] Other Applications As described above, the composite material (I) according to the present invention is preferably used for the electrode layer of an all-solid-state lithium ion secondary battery, but other than that, for example, a liquid lithium ion secondary battery. Electrode layer for secondary battery, electrode paste for lithium ion secondary battery, coating material for current collector for lithium ion secondary battery, material for catalyst layer and gas diffusion layer in fuel cell, electrode for redox flow battery, filler for reinforcing material , Fillers for heat conductive materials, fillers for electron conductive materials, etc. can also be suitably used. Further, it can be suitably used for applications such as ferromagnets, superconductors, wear-resistant members, and displays.

Hereinafter, examples and comparative examples of the present invention will be described, but these do not limit the technical scope of the present invention.
The method for evaluating the composite material of Examples and Comparative Examples, the method for producing a battery, the method for measuring the characteristics of a battery, and the raw materials used in each example are as follows.

[1] Evaluation of composite material [1-1] BET specific surface area Using NOVA2200e (registered trademark) manufactured by Quantachrome as a BET specific surface area measuring device, 3 g of a sample was placed in a sample cell (9 mm × 135 mm). The measurement was carried out after drying for 1 hour under vacuum conditions at 300 ° C. _{N 2} was used as the gas for measuring the BET specific surface area.

[1-2] 50% particle size (D _pV50 )
Using a Malvern Mastersizer 3000 (registered trademark) as a laser diffraction type particle size distribution measuring device, put a 5 mg sample in a container, add 10 g of water containing 0.04% by mass of a surfactant, and add 10 g for more than 5 minutes. Measurement was performed after ultrasonic treatment to obtain a _{50% particle size (D pV50} ) in the volume-based cumulative particle size distribution.

[1-3] Surface spacing d ₀₀₂
A mixture of vapor-phase carbon fiber and standard silicon (manufactured by NIST) mixed so as to have a mass ratio of 9: 1 was filled in a glass sample plate (sample plate window 18 × 20 mm, depth 0.2 mm). The measurement was performed under the following conditions.
XRD device: Rigaku SmartLab®
・ X-ray type: Cu-Kα ray ・ Kβ ray removal method: Ni filter ・ X-ray output: 45kV, 200mA
-Measurement range: 24.0 to 30.0 deg.
-Scan speed: 2.0 deg. / Min
_{The value of the surface spacing d 002} was obtained by applying the Gakushin method to the obtained waveform (see Iwashita et al., Carbon, vol. 42 (2004), p. 701-714). _{In the following Examples and Comparative Examples, the surface spacing d 002} does not change even if the vapor phase carbon fibers are coated with a metal oxide, that is, even if a composite material is formed.

[1-4] Average Thickness of Metal Oxide Layer The average thickness t of the metal oxide layer 22 was determined by the following method.
(1) One composite material A1 is randomly extracted from the composite materials observed by a transmission electron microscope (TEM).
(2) In the extracted composite material A1, one portion where the metal oxide layer 22 is formed is randomly selected, and the thickness t1 of the metal oxide layer 22 at the selected portion is measured. For the thickness t1, the intersection x1 between the line perpendicular to the surface of the vapor phase carbon fiber 21 and the surface of the vapor phase carbon fiber 21 and the intersection x2 between the vertical line and the outer periphery of the metal oxide layer 22 are obtained. , Obtained by measuring the distance between the obtained intersections x1 and x2.
(3) The above (1) and (2) are repeated 50 times. That is, the thicknesses t1 to t50 of the metal oxide layer 22 measured in the 50 composite materials A1 to A50 randomly extracted from the composite materials observed by TEM are measured. The randomly extracted composite materials A1 to A50 do not overlap with each other.
(4) Let the arithmetic mean value of the obtained values t1 to t50 be the average thickness t of the metal oxide layer 22.

The composite material was observed by TEM, and it was confirmed that the metal oxide layer was attached to the carbon fibers.

[1-5] Content of coating layer The mass of vapor-phase carbon fibers contained in the composite material was measured using a carbon / sulfur analyzer EMIA (registered trademark) -320V manufactured by HORIBA, Ltd., and was measured from the mass of the composite material. The content of the metal oxide was determined by subtracting it.

[1-6] Coverage by metal oxide layer The coverage was calculated from the binarized image obtained from the SEM image. The white area was adjusted to be the metal oxide layer.
Coverage = total area of white area / total area of particles x 100 [%]
In the present specification, the “coverage” is defined as being calculated by using the above equation from the binarization of the SEM image as described above.

The specific method is as follows. The image was acquired by adjusting the SEM so that the entire composite material could be seen. At that time, auto contrast was used. The acquired SEM image was opened in Photoshop (manufactured by Adobe), "image / mode / grayscale" was selected, and then "image / color tone correction / averaging (equalization)" was performed. Further, "image / color tone correction / two gradations" was selected, and the threshold value was set to 110 for execution. "Quick selection tool" was selected, "automatic adjustment" was checked, "hardness" was set to 100%, "interval" was set to 25%, and "diameter" was adjusted arbitrarily. The entire composite material was selected and "Record image / analysis / measurement" was selected to calculate the area. Then, a white area (recognized as one domain) was selected and the area was measured in the same manner. When there were multiple regions, all regions were measured one by one. The total area of all white areas was calculated. Here, the boundary of the range recognized as one domain is the place where the width of the white region is 0.1 μm or less. The above measurement was performed on 50 randomly extracted composite materials, and the average value was taken as the coverage ratio. Before selecting the "quick selection tool", select "image / analysis / set measurement scale / custom" and convert the value of the scale bar of the SEM image into pixels. However, the calculation of the coverage by binarizing the SEM image may be performed by using other software, or may be obtained from a composition analysis image or the like.

[2] Preparation of Battery Hereinafter, a method for producing a battery using the composite materials obtained in Examples and Comparative Examples will be described. Regarding each configuration of the battery produced here, those corresponding to the configurations with reference numerals shown in FIG. 1 will be described with reference numerals of the corresponding configurations.

[2-1] Preparation of solid electrolyte layer 12 In an argon gas atmosphere, the starting materials Li ₂ S (manufactured by Nippon Kagaku Kogyo Co., Ltd.) and P ₂ S ₅ (manufactured by Sigma-Aldrich Japan LLC) are mixed in a molar ratio of 75:25. Weigh and mix with, and perform mechanical milling (rotation speed 400 rpm) for 20 hours using a planetary ball mill (P-5 type, manufactured by Fritsch Japan Co., Ltd.) and zirconia balls (10 mm φ7, 3 mm φ10). _An amorphous solid electrolyte _{of Li 3} PS _{4 having} a pV50 of 0.3 μm was obtained.
The obtained amorphous solid electrolyte was press-molded by a uniaxial press molding machine using a polyethylene die having an inner diameter of 10 mmφ and a punch made of SUS to prepare a solid electrolyte layer 12 as a sheet having a thickness of 960 μm. ..

_{[2-2] Preparation of Negative Electrode Layer} 132 3 parts by mass of the composite material obtained in Examples and Comparative Examples and 48.5 parts by mass of artificial graphite (D pV50: 12 μm, BET: 1.8 m ^{2 /} g) made in China. _Was mixed with 48.5 parts by mass of a solid electrolyte (Li ₃ PS ₄ , D pV50: 8 μm). The mixture was homogenized by milling at 100 rpm for 1 hour using a planetary ball mill. The homogenized mixture was press-molded at 400 MPa by a uniaxial press molding machine using a polyethylene die having an inner diameter of 10 mmφ and a punch made of SUS to prepare a negative electrode layer 132 as a sheet having a thickness of 65 μm.

[2-3] Preparation of positive electrode layer 112 3 parts by mass of the composite material obtained in Examples and Comparative Examples, _{55 parts by mass of the positive electrode active material LiCoO 2} (manufactured by Nippon Kagaku Kogyo Co., Ltd., D _pV50 : 10 μm), and a solid 42 parts by mass of an electrolyte (Li ₃ PS ₄ , D _pV50 : 8 μm) was mixed. The mixture was homogenized by milling at 100 rpm for 1 hour using a planetary ball mill. The homogenized mixture was press-molded at 400 MPa by a uniaxial press molding machine using a polyethylene die having an inner diameter of 10 mmφ and a punch made of SUS to prepare a positive electrode layer 112 as a sheet having a thickness of 65 μm.

[2-4] Assembly of All-Solid Lithium Ion Secondary Battery 1 The negative electrode layer 132, the solid electrolyte layer 12, and the positive electrode layer 112 obtained above are laminated in this order in a die made of polyethylene having an inner diameter of 10 mmφ, and the negative electrode layer 132. A laminate A was obtained by sandwiching the negative electrode layer 132, the solid electrolyte layer 12, and the positive electrode layer 112 with punches made of SUS from both sides of the side and the positive electrode layer 112 side at a pressure of 100 MPa.
The obtained laminate A is once taken out from the die, and in the die, the negative electrode lead 131a, the copper foil (negative electrode current collector 131), the laminate A with the negative electrode layer 132 facing downward, and the aluminum foil ( The positive electrode current collector 111) and the positive electrode lead 111a are stacked in this order, sandwiched between both sides of the negative electrode lead 131a side and the positive electrode lead 111a side with a SUS punch at a pressure of 1 MPa, and the negative electrode lead 131a, copper foil, laminate A, and aluminum are sandwiched. The foil and the positive electrode lead 111a were joined to obtain an all-solid-state lithium ion secondary battery 1.

[3] Battery evaluation The following battery evaluations were all performed in the air at 25 ° C.

[3-1] Measurement of Coulomb Efficiency The all-solid-state lithium-ion secondary battery 1 manufactured as described above is constantly charged at 1.25 mA (0.05 C) from the rest potential to 4.2 V. rice field. Subsequently, a constant voltage charge of 4.2 V was performed for 40 hours. The sum of the charging capacities (unit: mAh) by constant current and constant voltage was defined as the initial charging capacity Q _c1 .
Next, constant current discharge was performed at 1.25 mA (0.05 C) until the voltage reached 2.75 V. The discharge capacity (unit: mAh) due to constant current discharge is defined as the initial discharge capacity Q _d1 . The value obtained by dividing the initial discharge capacity Q _d1 (mAh) by the mass of the active material in the positive electrode layer was defined as the initial discharge specific volume (unit: mAh / g).
Further, the initial discharge capacity Q _{d1 with respect to the initial charge capacity Q c1 was} defined as a percentage, and 100 × Q _d1 / Q _c1 was defined as the initial coulomb efficiency (%).

[3-2] Evaluation of 3C rate capacity retention rate Discharge capacity Q _{2.5d measured by constant current discharge at 2.5mA (0.1C) until it reaches 2.75V after charging in the same procedure as above.} (Unit: mAh) was measured. _{After charging in the same procedure as above, the discharge capacity Q 75d} (unit: mAh) measured by constant current discharge at 75 mA (3.0 C) until it reached 2.75 V was measured. 100 × Q _75d / Q _2.5d was defined as the 3C rate capacity retention rate (%).

[3-3] Evaluation of 100-cycle capacity retention rate Charging is performed with a constant current of 5.0 mA (0.2 C) until it reaches 4.2 V, and then at a constant voltage of 4.2 V, the current value is 1.25 mA. Constant voltage charging was performed until the voltage decreased to (0.05C). The discharge was performed with a constant current of 25 mA (1.0 C) until the voltage reached 2.75 V.
These charges and discharges were performed 100 times, and 100 × Q _d100 / Q _{d1 was defined} as the 100-cycle capacity retention rate (%) as the 100th discharge capacity Q d100.

[4] Raw Materials Details of the raw materials shown in Table 1 are as follows.

-VGCF (registered trademark) graphitized product: VGCF (registered trademark) -H, a vapor phase carbon fiber manufactured by Showa Denko KK, was used. The average fiber diameter D _{fa of} this carbon fiber is 150 nm, the BET specific surface area is 13 m ² / g, and d ₀₀₂ measured by XRD is 0.3380 nm.

[Examples 1 to 9, Comparative Examples 1 to 2]
In each Example and each Comparative Example, the raw materials shown in Table 1 were charged into a rolling fluid coating apparatus (MP-01_mini, manufactured by Paulec Co., Ltd.) at the ratio shown in Table 1, and the precursors were subjected to the conditions shown below and Table 1. The vapor phase carbon fibers were rolled and fluidized until the body solution was completely sprayed. As shown in Table 1, the obtained composite material was heat-treated in an electric tube furnace under the following conditions to obtain a composite material. Table 2 shows the physical characteristics of the obtained composite material and the results of battery evaluation.

Operating conditions of rolling flow coating equipment ・ Rotor: Standard ・ Filter: FPM
・ Mesh: 800M
・ Nozzle type: NPX-II
・ Nozzle diameter: 1.2 mm
・ Nozzle position: Tangent ・ Number of nozzles: 1
・ Rotor rotation speed: 400 rpm
-Spray nitrogen pressure: 0.17 (MPa)
・ Blow-off pressure: 0.2 (MPa)
-Filter removal time / interval: 4.0 / 0.3 (sec / sec)

Heat treatment conditions ・ Atmosphere: Argon ・ Maximum temperature: 400 ℃
・ Maximum temperature holding time: 1 hour ・ Temperature rise rate: 150 ℃ / h
・ Temperature drop rate: 150 ℃ / h

From Table 2, the following was found.
From Example 1, the composite material coated with lithium titanate under the conditions shown in Table 1 for the vapor phase carbon fiber VGCF (registered trademark) -H had a coverage of 50%. When this composite material was used as a component of the positive electrode layer and the negative electrode layer of the all-solid-state lithium ion secondary battery, the characteristics of the battery were evaluated as good.
From Example 2, even if the coverage with the metal oxide layer is 20%, the characteristics of the battery are sufficiently good.
From Example 3, even if the coverage with the metal oxide layer is 80%, the characteristics of the battery are sufficiently good.
From Example 4, even if the BET specific surface area of the composite material is 8.0 m ² / g, the characteristics of the battery are sufficiently good.
From Example 5, even if the BET specific surface area of the composite material is 6.6 m ² / g, the characteristics of the battery are sufficiently good.
From Example 6, even if the average thickness of the metal oxide layer is 50 nm, the characteristics of the battery are sufficiently good.
From Example 7, even if the average thickness of the metal oxide layer is 10 nm, the characteristics of the battery are sufficiently good.
From Example 8, even when lithium niobate is used as the metal oxide layer, the characteristics of the battery are good.
From Example 9, even when titanium oxide (amorphous) is used as the metal oxide layer, the characteristics of the battery are good. The characteristics of the battery are good without heat treatment.
From Comparative Example 1, when the coverage by the metal oxide layer is 10%, the characteristics of the battery are relatively poor.
From Comparative Example 2, if the coating with the metal oxide layer is not performed, the characteristics of the battery are relatively poor.

1: All-solid-state lithium-ion secondary battery 11: Positive electrode 111: Positive electrode current collector 111a: Positive electrode lead 112: Positive electrode layer 12: Solid electrolyte layer 13: Negative electrode 131: Negative electrode current collector 131a: Negative electrode lead 132: Negative electrode layer 2 : Composite material 21: Vapor phase carbon fiber 22: Metal oxide layer

Claims (15)

The vapor phase carbon fiber and the metal oxide layer that coats the surface of the vapor phase carbon fiber in a sea-island shape are included, and the coverage of the vapor phase carbon fiber by the metal oxide layer is 20% or more and 80%. Composite materials that are: The composite material according to claim 1, wherein the vapor phase carbon fibers are graphitized. The composite material according to claim 1 or 2, wherein the metal oxide layer has an average thickness of 10 nm or more. Any one of claims 1 to 3 in which the metal oxide constituting the metal oxide layer is contained in an amount of 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the vapor phase carbon fiber. The composite material described in the section. The metal oxides constituting the metal oxide layer are Li, Na, K, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, Pt and Ru. , Rh, Pd, Ag, Al, Ga, In, Tl, Sn and the composite material according to any one of claims 1 to 4, which comprises an oxide of a metal selected from Pb. The composite material according to any one of claims 1 to 5, wherein the metal oxide constituting the metal oxide layer contains at least one metal oxide selected from the group consisting of lithium titanate and lithium niobate. .. Any of claims 1 to 6 in which the BET specific surface area is 20.0 m ² _{/ g or less, and the average plane spacing d 002} of the (002) plane by X-ray diffraction measurement is 0.3354 nm or more and less than 0.3400 nm. The composite material according to item 1. The composite material according to any one of claims 1 to 7, wherein the average fiber diameter D _{fa is 100 nm or more and 300 nm or less.} The composite material according to any one of claims 1 to 8, further comprising at least one selected from the group consisting of a particulate conductive auxiliary agent, a fibrous conductive auxiliary agent, and solid electrolyte particles. An electrode layer for an all-solid-state lithium ion secondary battery containing the composite material, active material, and solid electrolyte according to any one of claims 1 to 9. The electrode for an all-solid-state lithium ion secondary battery including the electrode layer for the all-solid-state lithium ion secondary battery and the current collector according to claim 10. An all-solid-type lithium ion secondary battery having a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode and the negative electrode, wherein the negative electrode and the negative electrode An all-solid-state lithium-ion secondary battery in which either or both of the positive electrodes contain the composite material according to any one of claims 1 to 9. The method for producing a composite material according to any one of claims 1 to 9.
A step of preparing a precursor solution containing at least one metal oxide precursor selected from a metal alkoxide and a metal complex and a solvent.
A composite including a step of spraying the precursor solution on the gas phase carbon fiber in a fluid state and a step of heat-treating the vapor phase carbon fiber to which the metal oxide precursor is attached to form a metal oxide layer. Material manufacturing method. The method for producing a composite material according to any one of claims 1 to 9.
A step of preparing a precursor solution containing at least one metal oxide precursor selected from a metal alkoxide and a metal complex and a solvent.
A method for producing a composite material, which comprises a step of spraying the precursor solution onto the fluidized vapor phase carbon fibers and a step of forming a metal oxide layer from the metal oxide precursor by a sol-gel reaction. The method for producing a composite material according to claim 13 or 14, wherein the precursor solution further contains a lithium compound.

Images