JP2015133284A - Negative electrode material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode material for a nonaqueous electrolyte secondary battery, having the excellent long term cycle durability, while having a large capacity in comparison with a conventional graphite-based material and keeping a high initial efficiency which has been difficult in a conventional silicon-based material.SOLUTION: There is disclosed a negative electrode material used for a nonaqueous electrolyte secondary battery, which is obtained by that liquid organosiloxane is evaporated, and it is heated in the vapor phase at a temperature of 1,000°C or more to be thermally decomposed, then the thermal decomposition product is solidified on a substrate cooled to a temperature of 950°C or less.

Description

  The present invention relates to a negative electrode material used for a non-aqueous electrolyte secondary battery, a method for producing the same, and a negative electrode, a non-aqueous electrolyte secondary battery, and an electrochemical capacitor.

  Conventionally, non-aqueous electrolyte secondary batteries, in particular lithium ion secondary batteries, have been used for portable electronic devices, communication devices, and the like from the viewpoints of miniaturization, weight reduction, and economy. As a negative electrode material for such non-aqueous electrolyte secondary batteries, graphite-based materials with large capacity, high initial efficiency, and good cycle durability have been used. Therefore, there is a demand for a negative electrode material having a larger capacity. As one solution to such a demand, silicon-based negative electrode materials such as Si simple substance, SiO compound, and SiCO compound have been proposed.

  For example, Japanese Patent No. 2999741 (Patent Document 1) discloses a method using silicon oxide as a negative electrode material, and Japanese Patent No. 3072223 (Patent Document 2) deposits a silicon layer on a copper foil by chemical vapor deposition. A method is disclosed. In Japanese Patent No. 3060077 (Patent Document 3), the active material of the negative electrode is a silicon compound containing silicon and carbon or silicon, carbon, and oxygen obtained by heat treatment of an organic silicon compound at 100 to 3,000 ° C. In a non-aqueous electrolyte secondary battery, JP-A-10-74506 (Patent Document 4), a composition containing a siloxane polymer is thermally decomposed to form a ceramic material, and lithium ions are introduced into the ceramic material. A method of forming an electrode material for a lithium ion battery that includes forming the electrode material is disclosed. Furthermore, JP-A-2006-62949 (Patent Document 5) pulverizes a sintered product obtained by heating a silane and / or siloxane compound highly crosslinked by an addition reaction or the like under an inert air stream. A SiCO composite obtained as described above is disclosed. However, these have a drawback that long-term cycle durability of 300 cycles or more is poor, although the capacity is larger than that of conventional graphite-based materials.

Japanese Patent No. 2999741 Japanese Patent No. 3072223 Japanese Patent No. 3060077 JP-A-10-74506 JP 2006-62949 A

  The present invention has been made in view of the above circumstances, has a large capacity compared to conventional graphite-based materials, and has good long-term cycle durability while maintaining high initial efficiency, which was difficult with conventional silicon-based materials. It aims at providing the negative electrode material for nonaqueous electrolyte secondary batteries.

  As a result of intensive studies to achieve the above object, the present inventor has vaporized liquid organosiloxane, heated to 1,000 ° C. or higher in the gas phase and thermally decomposed, and then reduced the thermal decomposition product to 950 ° C. or lower. By solidifying on a cooled substrate and forming a solid SiCO-based composite on the substrate, a negative electrode material for a non-aqueous electrolyte secondary battery having good long-term cycle durability while maintaining high capacity and high initial efficiency Has been found to yield the present invention.

Accordingly, the present invention provides the following.
[1]. A negative electrode material used for a non-aqueous electrolyte secondary battery, in which liquid organosiloxane is vaporized, heated to 1,000 ° C. or higher in the gas phase and thermally decomposed, and then the pyrolyzed product is reduced to 950 ° C. or lower. A negative electrode material for a non-aqueous electrolyte secondary battery obtained by solidifying on a cooled substrate.
[2]. The negative electrode material for a nonaqueous electrolyte secondary battery according to [1], wherein the liquid organosiloxane is an organosiloxane having 2 to 6 silicon atoms in one molecule.
[3]. The negative electrode material for a nonaqueous electrolyte secondary battery according to [1] or [2], wherein the liquid organosiloxane is a cyclic organosiloxane having 4 to 6 silicon atoms in one molecule.
[4]. The negative electrode material for nonaqueous electrolyte secondary batteries according to any one of [1] to [3], wherein the pressure atmosphere for thermal decomposition is 10 Pa to 10 kPa.
[5]. The silicon content is 50 to 70 mass%, the bonded carbon content is 1 mass% or more, the total carbon content is 1 to 20 mass%, and the oxygen content is 25 to 40 mass%, [1] to [4] ] The negative electrode material for nonaqueous electrolyte secondary batteries in any one of.
[6]. A negative electrode for a nonaqueous electrolyte secondary battery, comprising the negative electrode material for a nonaqueous electrolyte secondary battery according to any one of [1] to [5].
[7]. After vaporizing the liquid organosiloxane and heating it in the gas phase to 1,000 ° C or higher and thermally decomposing it, the pyrolyzate is solidified on the metal foil cooled to 950 ° C or lower and solidified on the metal foil. A negative electrode for a non-aqueous electrolyte secondary battery having a film formed thereon.
[8]. A nonaqueous electrolyte secondary battery comprising the negative electrode according to [6] or [7], a positive electrode, and an electrolytic solution.
[9]. An electrochemical capacitor having a negative electrode including a negative electrode material, a positive electrode, and an electrolytic solution, wherein the negative electrode material vaporizes liquid organosiloxane and is thermally decomposed by heating it to a temperature of 1,000 ° C. or higher in the gas phase. An electrochemical capacitor, which is a negative electrode material obtained by solidifying the pyrolyzate on a substrate cooled to 950 ° C. or lower.
[10]. A non-aqueous electrolyte characterized in that liquid organosiloxane is vaporized, heated to 1,000 ° C. or higher in the gas phase and thermally decomposed, and then the pyrolyzed product is solidified on a substrate cooled to 950 ° C. or lower. A method for producing a negative electrode material for a secondary battery.

  In the present invention, the “SiCO compound” refers to a pure substance whose composition formula is represented by SiCxOy (0 <x <1, 0 <y <2). The “SiCO composite” refers to a mixture containing a SiCO compound (for example, a mixture of a SiCO compound and carbon).

  By using the negative electrode material for a non-aqueous electrolyte secondary battery of the present invention, a non-aqueous electrolyte secondary battery and an electrochemical capacitor having a high capacity and excellent long-term cycle durability can be obtained.

It is a manufacturing apparatus schematic diagram concerning one example of the present invention. It is the cooling chamber schematic of the manufacturing apparatus which concerns on one Example of this invention. 3 is an X-ray diffraction (Cu—Kα) chart of the powder obtained in Example 1. FIG. 4 is an X-ray diffraction (Cu—Kα) chart of the powder obtained in Example 2. FIG. 4 is an X-ray diffraction (Cu—Kα) chart of the powder obtained in Example 3. FIG. 4 is an X-ray diffraction (Cu—Kα) chart of the powder obtained in Example 4. FIG.

Hereinafter, the present invention will be described in detail.
[Negative electrode material]
The present invention is obtained by vaporizing a liquid organosiloxane, heating it in the gas phase to 1,000 ° C. or higher, and thermally decomposing it, and then coagulating the pyrolyzate on a substrate cooled to 950 ° C. or lower. It is a solid SiCO composite and is used as a negative electrode material (negative electrode active material).

[I] Liquid organosiloxane is vaporized and heated to 1000 ° C. or higher in the gas phase for thermal decomposition.
As the first feature of the present invention, it is indispensable to vaporize the liquid organosiloxane and heat the vaporized organosiloxane to 1000 ° C. or higher in the gas phase for thermal decomposition. In the conventionally known method of thermally decomposing organosiloxane solids in the solid phase, if pyrolysis is performed at a low temperature, the decomposition is insufficient, so that a portion causing a side reaction during charge and discharge remains and the initial efficiency is lowered. For this reason, although it is necessary to decompose at a high temperature of 1,000 ° C. or higher, there is a problem that long-term cycle durability is deteriorated when pyrolysis is performed at high temperature. As the main cause, it is conceivable that the thermal decomposition at a high temperature leads to crystallization, so that the relaxation action of expansion and contraction due to an incomplete lattice is reduced, and the long-term cycle durability is lowered. In the method in which the liquid organosiloxane of the present invention is vaporized and then thermally decomposed in the gas phase, crystallization does not occur in the gas phase even at high temperatures. A negative electrode material for a non-aqueous electrolyte secondary battery having good long-term cycle durability while maintaining high initial efficiency can be obtained.

It does not specifically limit as liquid organosiloxane, It can use individually by 1 type or selecting 2 or more types suitably. An organosiloxane having 2 to 6 silicon atoms in one molecule is preferred. If the number of silicon atoms in the organosiloxane molecule is greater than 6, vaporization may be difficult. Organosiloxanes with 2 to 6 silicon atoms in one molecule have advantages in industrial scale production in that the yield of the obtained SiCO compound is increased, it is chemically stable at room temperature, and handling and quantitative supply are easy. There is also. Specifically, octamethylcyclotetrasiloxane (D ₄ ), decamethylcyclopentasiloxane (D ₅ ), dodecamethylcyclohexasiloxane (D ₆ ), tetramethylcyclotetrasiloxane (H ₄ ), octamethyltrisiloxane ( MDM), hexamethyldisiloxane (M ₂ ), etc., and cyclic organos such as octamethylcyclotetrasiloxane (D ₄ ), decamethylcyclopentasiloxane (D ₅ ), dodecamethylcyclohexasiloxane (D ₆ ), etc. Siloxane, particularly cyclic organosiloxane having 4 to 6 silicon atoms is preferred.

  The conditions for vaporizing the liquid organosiloxane are appropriately selected depending on the liquid organosiloxane to be used, and are not particularly limited as long as the temperature is less than 1,000 ° C. However, 30 to 300 ° C is preferable, and the pressure is preferably in the range of 10 Pa to 0.1 MPa. .

  Although it heats to 1,000 degreeC or more and thermally decomposes in a gaseous phase, 1,000-1500 degreeC is preferable and 1,100-1,400 degreeC is more preferable. If it is less than 1,000 ° C., thermal decomposition is insufficient and the initial efficiency is lowered, and if it exceeds 1,500 ° C., a large amount of Si—C bonds are produced and the capacity is lowered.

  The pressure atmosphere for thermal decomposition is preferably 10 Pa to 110 kPa, and more preferably a reduced pressure atmosphere of 10 Pa to 10 kPa. 10 Pa or more is preferable from the viewpoint of reactivity, and 110 kPa or less is preferable because fine powder is generated in the gas phase and taken into the deposit on the substrate, which may reduce long-term cycle durability.

  The vaporized organosiloxane can be thermally decomposed by being accompanied by a carrier gas. As the carrier gas, it is preferable to use an inert gas such as argon gas or a reducing gas such as hydrogen gas.

[II] After pyrolysis, solidify on a substrate cooled to 950 ° C. or lower.
As a second feature of the present invention, it is essential to solidify the pyrolyzate on a substrate cooled to 950 ° C. or lower. The temperature of the gaseous pyrolyzate is lowered by the cooled substrate, is supersaturated and solidified on the surface of the substrate, and can be recovered as a solid SiCO-based composite. Furthermore, by making a pyrolyzate into 950 degrees C or less, the crystal growth after solidification can be suppressed and the negative electrode material for nonaqueous electrolyte secondary batteries excellent in long-term cycle durability can be obtained. The lower limit of the cooled substrate temperature is preferably 100 ° C. or more from the viewpoint of initial cycle durability up to 50 cycles, and the substrate temperature is more preferably 200 to 900 ° C. The substrate temperature can be measured with a thermometer installed on the substrate.

  As an apparatus for producing a negative electrode material of the present invention, an apparatus shown in FIG. 1 is exemplified. Hereinafter, it will be described in more detail with reference to FIG. The raw material tank 1 is connected to the vaporizing unit 3 via the liquid mass flow controller 2, and separately, the gas mass flow controller 4 is connected to the vaporizing unit 3. The vaporizer 3 is provided with a vaporizer heater 5 to adjust the vaporizer 3 to a predetermined temperature. The vaporizing unit 3 is connected to the furnace inlet side of the furnace core tube 6, and a cooling chamber 7 </ b> A is connected to the furnace outlet side of the furnace core tube 6. A furnace core tube heater 8 is disposed in the furnace core tube 6 to adjust the furnace core tube 6 to a predetermined temperature. Inside the cooling chamber 7A, a rotatable columnar substrate 9, a scraper 10, and a recovery container 11 are disposed below. The columnar substrate 9 is rotated by a motor 12 at a predetermined speed, and a refrigerant circulation ( (Not shown). The interior of the furnace core tube 6 and the cooling chamber 7A is decompressed by a mechanical booster pump 13 and an oil rotary vacuum pump 14, and is adjusted to a predetermined pressure by a butterfly valve 15.

  The liquid organosiloxane which is a raw material is put in the raw material tank 1 and is supplied from the raw material tank 1 to the vaporization unit 3 at a constant speed by the liquid mass flow controller 2. The vaporization section 3 is heated to a predetermined vaporization temperature by the vaporization section heater 5 so that the liquid organosiloxane is completely vaporized. On the other hand, a carrier gas is supplied to the vaporizing unit 3 by a gas mass flow controller 4 at a constant speed. The liquid organosiloxane vaporized in the vaporization section 3 is accompanied by the carrier gas and supplied to the furnace inlet side of the furnace core tube 6 connected to the vaporization section 3. The interior of the furnace core tube 6 is heated to a predetermined temperature by a furnace core tube heater 8. The vaporized liquid organosiloxane is thermally decomposed inside the furnace core tube 6, and the pyrolysis gas passes through the furnace outlet side of the furnace core tube 6, reaches the cooled cylindrical substrate 9 in the cooling chamber 7 </ b> A, and is cooled. Solidify and deposit on the cylindrical substrate 9. The solid SiCO composite deposited on the columnar substrate 9 is rotated when the columnar substrate 9 is rotated, scraped off by the scraper 10, and collected in the collection container 11.

  The composition of the obtained solidified product (hereinafter referred to as SiCO-based composite) can be adjusted by changing the composition of the liquid organosiloxane as a raw material, the thermal decomposition temperature, and the thermal decomposition atmosphere pressure. For example, if the thermal decomposition temperature is less than 1,300 ° C., the total carbon amount decreases as the temperature increases, but if it exceeds 1,300 ° C., the total carbon amount increases as the temperature increases. Moreover, when the pressure is high, the total amount of carbon increases. Specifically, the silicon content is 50 to 70 mass%, the bound carbon content is 1 mass% or more, preferably 1 to 15 mass%, the total carbon content is 1 to 20 mass% or less, and oxygen The content is preferably 25 to 40% by mass. If the silicon content is less than 50% by mass, the capacity may decrease, and if it is greater than 70% by mass, the long-term cycle durability may decrease. If the amount of bonded carbon is less than 1% by mass, the long-term cycle durability may be reduced, and if the total amount of carbon is more than 20% by mass, the capacity may be reduced. If the amount of oxygen is less than 25% by mass, the long-term cycle durability may decrease, and if it exceeds 40% by mass, the initial efficiency may decrease. The amount of silicon is measured by a fluorescent X-ray analysis method, and the amount of oxygen is measured by melting in a graphite crucible in an inert gas-infrared absorption method. Further, the amount of bonded carbon and the total amount of carbon are measured by combustion in an oxygen stream-infrared absorption method. The amount of bonded carbon is determined by subtracting the amount of free carbon from the total amount of carbon. In the measurement of the total carbon content, the combustion temperature is set to a high temperature, and in the measurement of the free carbon content, the combustion temperature is set to a low temperature. As a specific example, the total carbon amount is measured at a furnace temperature of 1,350 ° C. by adding an Sn catalyst, and the free carbon amount is measured at a furnace temperature of 850 ° C. without a catalyst.

  Confirmed from the fact that the diffraction pattern of X-ray diffraction (Cu-Kα) using, for example, copper as the counter cathode has a peak near 2θ = 25 ° and a broad peak appearing at 50 to 70 ° for the SiCO composite. it can. The latter peak position varies depending on the composition, and tends to be closer to a higher angle as x increases.

The obtained SiCO-based composite can be used as a negative electrode material (negative electrode active material) for non-aqueous electrolyte secondary batteries. If necessary, it is preferably pulverized by a known means such as a ball mill or a jet mill to form a powdered negative electrode material. The average particle size of the powder is preferably from 0.1 to 100 μm, more preferably from 0.5 to 20 μm. The average particle diameter is a value measured as a weight average value D ₅₀ (that is, a particle diameter (median diameter) when the cumulative weight is 50%) in the particle size distribution measurement by the laser light diffraction method.

  Furthermore, in order to impart conductivity, it is preferable to perform carbon coating on the obtained powdered SiCO composite by chemical vapor deposition or mechanical alloying. In addition, when carbon coating is performed, the ratio of the carbon coating amount to the total mass of the carbon-coated powder is preferably 1 to 50% by mass, and more preferably 1 to 20% by mass.

  In the chemical vapor deposition treatment, hydrocarbon compound gas and / or steam is introduced into the vapor deposition reactor in a temperature range of 600 ° C. to 950 ° C., more preferably in a temperature range of 800 ° C. to 900 ° C. under normal pressure or reduced pressure. It can be carried out by introducing a known thermal chemical vapor deposition process or the like. As this hydrocarbon compound, a compound that generates carbon by pyrolysis within the above heat treatment temperature range is selected. For example, in addition to methane, ethane, propane, butane, pentane, hexane, etc., hydrocarbons such as ethylene, propylene, butylene, acetylene, etc., or alcohol compounds such as methanol, ethanol, benzene, toluene, xylene, styrene 1- to 3-ring aromatic hydrocarbons such as ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, or a mixture thereof. Gas gas oil, creosote oil, anthracene oil, and naphtha cracked tar oil obtained in the tar distillation step can be used alone or as a mixture.

[Negative electrode]
A negative electrode for a non-aqueous electrolyte secondary battery including the obtained negative electrode material for a non-aqueous electrolyte secondary battery made of a SiCO-based composite can be obtained. For example, as a manufacturing method of a negative electrode (molded body), N-methylpyrrolidone or water may be used for the powdered negative electrode material, a binder such as a polyimide resin, a conductive agent as necessary, and other additives. A negative electrode can be obtained by kneading a solvent suitable for dissolving and dispersing the binder into a paste-like mixture, applying the mixture to a current collector such as a metal foil, and drying. The content of the negative electrode material of the present invention is preferably 30 to 90% by mass with respect to the negative electrode (molded body (excluding the current collector)).

  The type of the conductive agent is not particularly limited as long as it is an electron-conductive material that does not decompose or change in the configured battery. Specifically, metal powder such as Al, Ti, Fe, Ni, Cu, Zn, Ag, Sn, Si, metal fiber or natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor grown carbon fiber, Graphite such as pitch-based carbon fiber, PAN-based carbon fiber, and various resin fired bodies can be used. The conductive agent of the negative electrode material of the present invention is preferably 0 to 50% by mass with respect to the negative electrode (excluding the molded body (current collector)).

  As the metal foil, copper, SUS, or nickel is preferable as the material having high conductivity, high strength, and oxidation resistance, and copper is most preferable. The thickness of the metal foil is preferably 3 to 30 μm. If it is thinner than 3 μm, the strength as an electrode is insufficient, and if it is thicker than 30 μm, the battery capacity density is lowered.

  Further, as one embodiment of the present invention, the SiCO composite can be directly solidified on a metal foil which is a negative electrode current collector, and a thin film of the SiCO composite can be formed on the metal foil. That is, liquid organosiloxane is vaporized, heated to 1,000 ° C. or higher in the gas phase and thermally decomposed, and then the pyrolyzed product is solidified on a metal foil cooled to 950 ° C. or lower to form a metal foil. A negative electrode for a non-aqueous electrolyte secondary battery having a solidified film formed thereon can also be used. By this method, it is possible to strengthen the bonding between the SiCO composite as the negative electrode active material and the metal foil as the current collector, and the non-aqueous electrolyte secondary excellent in short-term and long-term cycle durability and rate characteristics. A negative electrode for a battery is obtained. The surface of the metal foil is preferably roughened by a known method such as a mechanical or chemical method in order to improve adhesion with the thin film of the SiCO-based composite.

  As an apparatus used in this case, an apparatus in which the cooling chamber 7A of the manufacturing apparatus shown in FIG. 1 is replaced with a cooling chamber 7B shown in FIG. Hereinafter, it will be described in more detail with reference to FIG. Inside the cooling chamber 7B, a cooling drum 16, a feed roll 17, and a take-up roll 18 cooled by refrigerant circulation are arranged, and a metal foil 19 is fed from the feed roll 17 and passes through the surface of the cooling drum 16. It is installed so that it can be wound by the winding roll 18. A motor 20, a brake 21, and a motor 22 with a clutch are attached to the cooling drum 16, the feeding roll 17, and the take-up roll 18, respectively, so that the metal foil 19 travels at a constant speed and tension and is predetermined by the cooling drum 16. Is cooled to a temperature of The pyrolyzate (gas) reaches the metal foil 19 on the surface of the cooling drum 16 in the cooling chamber 7B, is cooled and solidifies, and is deposited as a thin film on the surface of the metal foil 19.

  The metal foil needs to be cooled to 950 ° C. or lower, and more preferably 900 ° C. or lower. In the case where the metal foil is a copper foil, the temperature is preferably 500 ° C. or lower because copper crystals may grow and the strength of the copper foil may decrease. The lower limit is preferably 100 ° C. or higher, and more preferably 200 ° C. or higher.

  The thickness of the thin film of the SiCO-based composite is preferably 1 μm or more from the viewpoint of electric capacity, and preferably 50 μm or less from the viewpoint of preventing the metal foil from tearing. Furthermore, 3-40 micrometers is preferable.

[Nonaqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention has the above-described negative electrode, positive electrode, and electrolytic solution, and is characterized in that the negative electrode of the present invention is used. Other positive electrode, electrolyte, separator and other materials and battery shape Etc. can use well-known things and are not limited. For example, as the positive electrode active material, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiFePO ₄ , V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS _2, etc. These transition metal oxides, lithium and chalcogen compounds are used. As the electrolyte, a non-aqueous solution containing a lithium salt such as lithium hexafluorophosphate, lithium perchlorate, lithium borofluoride, lithium hexafluoroarsenate is used, and propylene carbonate, ethylene carbonate, dimethyl is used as the non-aqueous solvent. A single substance such as carbonate, diethyl carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran, or a combination of two or more kinds is used. Various other non-aqueous electrolytes and solid electrolytes can also be used.

[Electrochemical capacitor]
In addition, a liquid organosiloxane is vaporized, heated to 1,000 ° C. or higher in the gas phase, thermally decomposed, and then solidified on a substrate cooled to 950 ° C. or lower, and a negative electrode including a negative electrode material, a positive electrode, An electrochemical capacitor having an electrolytic solution can also be manufactured. The preferred range of the negative electrode material is the same as described above. In this case, the electrochemical capacitor to be manufactured is characterized in that the negative electrode of the present invention is used, and other materials such as positive electrode, electrolyte, separator, and capacitor shape can be used, and are not limited. For example, activated carbon, carbon nanofibers, carbon nanotubes and the like are used as the positive electrode active material, and lithium electrolytes such as lithium hexafluorophosphate, lithium perchlorate, lithium borofluoride, and lithium hexafluoroarsenate are used as the electrolyte. A non-aqueous solution containing is used. As the non-aqueous solvent, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran and the like are used alone or in combination of two or more. Various other non-aqueous electrolytes and solid electrolytes can also be used.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1]
The manufacturing apparatus shown in FIG. 1 was used. While the inside of the alumina furnace core tube 6 having an inner diameter of 120 mm and a length of 1,800 mm is evacuated to 10 Pa by the oil rotary vacuum pump 14, the center part of the furnace core tube 6 becomes 1,200 ° C. (decomposition temperature). Heated. Liquid octamethylcyclotetrasiloxane (D ₄ ) was vaporized by heating to 250 ° C. under a reduced pressure of 100 Pa in the vaporizing section 3, and then entrained with 2 NL / min of argon gas as a carrier gas. It was supplied into the core tube 6 at a rate of 1 g / min. The butterfly valve was adjusted so that the pressure in the furnace core tube 6 at this time was 100 Pa. Octamethylcyclotetrasiloxane was thermally decomposed at the center of the furnace core tube 6 and then deposited on the cylindrical substrate 9 cooled to 900 ° C. (substrate temperature) in the cooling chamber 7A connected to the furnace outlet side. . This deposit was collected and pulverized with a ball mill to an average particle size of 10 μm. When this powder was subjected to X-ray diffraction (Cu-Kα) using copper as the counter cathode, the diffraction pattern shown in FIG. 3 was obtained, and a peak indicating that it was a SiCO-based composite was confirmed. Silicon content with a fluorescent X-ray analyzer (PHILIPS X-ray spectrometer MagiX PRO), carbon content with a carbon analyzer (Horiba carbon analyzer EMIA-110), total carbon content, oxygen analyzer (Horiba oxygen / nitrogen analyzer-2) Table 1 shows the results of measuring the amount of oxygen in).

Next, 45 parts by mass of artificial graphite (average particle size 10 μm) and 56 parts by mass of polyimide resin (trade name: U-varnish A, solid content 18% by mass) are added to 45 parts by mass of the obtained powder, and N -Methyl-2-pyrrolidone was added and stirred to a slurry. This slurry was applied to a copper foil having a thickness of 12 μm with a doctor blade, dried at 80 ° C. for 1 hour, then pressure-formed by a roller press, and further vacuum dried at 350 ° C. for 1 hour. This was punched into a circle with an area of 2 cm ² to produce a negative electrode.

[Example 2]
A negative electrode material powder was prepared in the same manner as in Example 1 except that the decomposition temperature was 1,500 ° C. When this powder was analyzed with an X-ray diffractometer, the diffraction pattern shown in FIG. 4 was obtained, and a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 3]
A negative electrode material powder was produced in the same manner as in Example 1 except that the decomposition temperature was 1,000 ° C. When this powder was analyzed with an X-ray diffractometer, the diffraction pattern shown in FIG. 5 was obtained, and a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 4]
A negative electrode material powder was prepared in the same manner as in Example 1 except that the atmospheric pressure was 9,000 Pa. When this powder was analyzed with an X-ray diffractometer, the diffraction pattern shown in FIG. 6 was obtained, and a peak indicating that it was a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 5]
A negative electrode material powder was prepared in the same manner as in Example 1 except that the carrier gas was hydrogen gas. When this powder was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 6]
A negative electrode material powder was prepared in the same manner as in Example 1 except that the liquid organosiloxane was decamethylcyclopentasiloxane (D ₅ ). When this powder was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 7]
A negative electrode material powder was prepared in the same manner as in Example 1 except that the liquid organosiloxane was changed to dodecamethylcyclohexasiloxane (D ₆ ). When this powder was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 8]
A negative electrode material powder was prepared in the same manner as in Example 1 except that tetramethylcyclotetrasiloxane (H ₄ ) was used as the liquid organosiloxane. When this powder was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 9]
A negative electrode material powder was prepared in the same manner as in Example 1 except that octamethyltrisiloxane (MDM) was used as the liquid organosiloxane. When this powder was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 10]
A negative electrode material powder was prepared in the same manner as in Example 1 except that hexamethyldisiloxane (M ₂ ) was used as the liquid organosiloxane. When this powder was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results of measuring the silicon amount, the bound carbon amount, the total carbon amount, and the oxygen amount in the same manner as in Example 1. Next, a negative electrode was produced from this powder in the same manner as in Example 1.

[Example 11]
Using the apparatus in which the cooling chamber 7A of the manufacturing apparatus shown in FIG. 1 is replaced with the cooling chamber 7B shown in FIG. 2, a 12 μm thick copper foil whose surface has been roughened is fed from the feeding roll 17 and the surface of the cooling drum 16 The octamethylcyclotetrasiloxane (D ₄ ) is thermally decomposed at 1,200 ° C. (decomposition temperature) in the same manner as in Example 1 while traveling so as to be wound by the winding roll 18 via It was deposited on the surface of the copper foil cooled to (substrate temperature). When this deposit was analyzed with an X-ray diffractometer, a peak indicating a SiCO composite was confirmed. Table 1 shows the results obtained by scraping and collecting the deposit and measuring the silicon content, the bound carbon content, the total carbon content, and the oxygen content. Next, the deposit was punched into a circle with an area of 2 cm ² while the deposit was in close contact with the copper foil (film thickness 32 μm (including copper foil)) to produce a negative electrode.

[Comparative Example 1]
A SiCO composite powder was obtained by the method described in Example 1 of JP-A-2006-62949. That is, platinum chloride was added to a curable siloxane mixture consisting of 120 g of tetramethyltetravinylcyclotetrasiloxane [manufactured by Shin-Etsu Chemical Co., Ltd., LS-8670] and 80 g of methyl hydrogen siloxane [manufactured by Shin-Etsu Chemical Co., Ltd., KF-99]. 0.1 g of acid catalyst [chloroplatinic acid 1% solution] was added and mixed well. Then, it was pre-cured at 60 ° C. all day and night. It was put in a glass container as it was, and heated at 200 ° C. for 2 hours in a muffle furnace with a temperature program capable of controlling the atmosphere in a nitrogen atmosphere to be completely cured. This cured product was finely pulverized by a ball mill so that the average particle size became 10 μm. Then, it put into the alumina container with a lid | cover, and baked at 1,000 degreeC for 3 hours by the muffle furnace with a temperature program which can control atmosphere in nitrogen atmosphere. After cooling, the mixture was pulverized by a pulverizer (mass colloider) having a clearance of 20 μm to obtain a SiCO composite powder having an average particle size of about 10 μm. Next, a circular negative electrode (area 2 cm ² ) was produced in the same manner as in Example 1 except that this powder was used.

[Battery evaluation]
The evaluation as the negative electrode active material of the lithium ion secondary battery was the same in all Examples and Comparative Examples, and was performed by the following methods and procedures.
<Evaluation of initial charge / discharge characteristics>
In order to evaluate the initial charge / discharge characteristics of the obtained negative electrode, a lithium foil was used as a counter electrode, and lithium hexafluorophosphate was used as a non-aqueous electrolyte in a 1/1 (volume ratio) mixture of ethylene carbonate and diethyl carbonate. A non-aqueous electrolyte solution dissolved at a concentration of mol / L was used, and a half cell for evaluation using a microporous polyethylene film having a thickness of 30 μm as a separator was produced.
The prepared half cell was left overnight at room temperature, and then charged using a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.) at a constant current of 1.5 mA until the cell voltage reached 5 mV. After reaching the value, charging was performed by decreasing the current so as to keep the cell voltage at 5 mV, and when the current value fell below 200 μA, the charging was terminated and the charging capacity was determined. The discharge was performed at a constant current of 0.6 mA, and when the cell voltage exceeded 2.0 V, the discharge was terminated and the discharge capacity was determined. The obtained discharge capacity was divided by the charge capacity to obtain the initial efficiency. These results are shown in Table 2. In addition, the discharge capacity and the charge capacity in Table 2 are the capacity per 1 g of the SiOC composite excluding the graphite added for imparting conductivity.

<< Long-term cycle durability evaluation >>
In order to evaluate the cycle durability of the obtained negative electrode, 3 parts by mass of acetylene black and 3 parts by mass of polyvinylidene fluoride were added to 94 parts by mass of lithium cobaltate as a positive electrode material, and N-methyl-2-pyrrolidone was further added. The slurry was stirred. This slurry was applied to an aluminum foil having a thickness of 16 μm with a doctor blade, dried at 100 ° C. for 1 hour, pressure-formed with a roller press, and further dried in vacuo at 120 ° C. for 5 hours. This was punched into a circle with an area of 2 cm ² to produce a positive electrode. Using this positive electrode and the above negative electrode, a nonaqueous electrolyte solution in which lithium hexafluorophosphate was dissolved in a 1/1 (volume ratio) mixture of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / L as a nonaqueous electrolyte was used. A full cell for evaluation using a polyethylene microporous film having a thickness of 30 μm as a separator was prepared.

DESCRIPTION OF SYMBOLS 1 Raw material tank 2 Liquid mass flow controller 3 Vaporization part 4 Gas mass flow controller 5 Vaporization part heater 6 Furnace core pipe 7A, 7B Cooling chamber 8 Furnace core pipe heater 9 Cylindrical base | substrate 10 Scraper 11 Recovery container 12 Motor 13 Mechanical booster pump 14 Oil rotation Vacuum pump 15 Butterfly valve 16 Cooling drum 17 Feeding roll 18 Winding roll 19 Metal foil 20 Motor 21 Brake 22 Motor with clutch

Claims (10)

  A negative electrode material used for a non-aqueous electrolyte secondary battery, in which liquid organosiloxane is vaporized, heated to 1,000 ° C. or higher in the gas phase and thermally decomposed, and then the pyrolyzed product is reduced to 950 ° C. or lower. A negative electrode material for a non-aqueous electrolyte secondary battery obtained by solidifying on a cooled substrate.   The negative electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the liquid organosiloxane is an organosiloxane having 2 to 6 silicon atoms in one molecule.   The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the liquid organosiloxane is a cyclic organosiloxane having 4 to 6 silicon atoms in one molecule.   The negative electrode material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the pressure atmosphere for thermal decomposition is 10 Pa to 10 kPa.   The silicon content is 50 to 70 mass%, the bonded carbon content is 1 mass% or more, the total carbon content is 1 to 20 mass%, and the oxygen content is 25 to 40 mass%. The negative electrode material for a nonaqueous electrolyte secondary battery according to any one of the preceding claims.   The negative electrode for nonaqueous electrolyte secondary batteries containing the negative electrode material for nonaqueous electrolyte secondary batteries of any one of Claims 1-5.   After vaporizing the liquid organosiloxane and heating it in the gas phase to 1,000 ° C or higher and thermally decomposing it, the pyrolyzate is solidified on the metal foil cooled to 950 ° C or lower and solidified on the metal foil. A negative electrode for a non-aqueous electrolyte secondary battery having a film formed thereon.   A nonaqueous electrolyte secondary battery comprising the negative electrode according to claim 6 or 7, a positive electrode, and an electrolytic solution.   An electrochemical capacitor having a negative electrode including a negative electrode material, a positive electrode, and an electrolytic solution, wherein the negative electrode material vaporizes liquid organosiloxane and is thermally decomposed by heating it to a temperature of 1,000 ° C. or higher in the gas phase. An electrochemical capacitor, which is a negative electrode material obtained by solidifying the pyrolyzate on a substrate cooled to 950 ° C. or lower.   A non-aqueous electrolyte characterized in that liquid organosiloxane is vaporized, heated to 1,000 ° C. or higher in the gas phase and thermally decomposed, and then the pyrolyzed product is solidified on a substrate cooled to 950 ° C. or lower. A method for producing a negative electrode material for a secondary battery.

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