JP2013008696A - Method of manufacturing negative electrode material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide negative electrode material for a nonaqueous electrolyte secondary battery and a method of manufacturing the same enabling manufacture of a negative electrode of a lithium ion secondary battery having higher cycle characteristics and rate characteristics than conventional one, and to provide the lithium ion secondary battery and an electrochemical capacitor.SOLUTION: Negative electrode material for a secondary battery using nonaqueous electrolyte comprises a chemical element except silicon and oxygen at concentration of 50 to 100,000 ppm, in at least one of: silicon oxide represented by a general formula SiO(x=0.5 to 1.6); a silicon composite where Si/O having such a structure that silicon is dispersed into silicon dioxide has a molar ratio of 1/0.5 to 1.6; and a compound of the silicon oxide and the silicon composite.

Description

  The present invention provides a negative electrode material for a non-aqueous electrolyte secondary battery that exhibits good cycle characteristics when used as a negative electrode active material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery or an electrochemical capacitor, and a method for producing the same. The present invention also relates to a lithium ion secondary battery and an electrochemical capacitor.

In recent years, with the remarkable development of portable electronic devices, communication devices, etc., secondary batteries with high energy density are strongly demanded from the viewpoints of economy and downsizing and weight reduction of devices.
Conventionally, as a measure for increasing the capacity of this type of secondary battery, for example, a method using an oxide such as V, Si, B, Zr, Sn, or a composite oxide thereof as a negative electrode material (for example, Patent Documents 1 and 2). Etc.), a method of applying a melt-quenched metal oxide as a negative electrode material (for example, see Patent Document 3), a method of using silicon oxide as a negative electrode material (for example, see Patent Document 4), and Si _{2 as} a negative electrode material. A method using N ₂ O and Ge ₂ N ₂ O (see, for example, Patent Document 5) is known.
In addition, for the purpose of imparting conductivity to the negative electrode material, a method of carbonizing SiO with graphite and then carbonizing (for example, see Patent Document 6), a method of coating a carbon layer on the surface of silicon particles by chemical vapor deposition (For example, refer patent document 7 grade | etc.,), And the method (For example, refer patent document 8 grade | etc.) Which coat | covers a carbon layer by the chemical vapor deposition method on the silicon oxide particle surface.

  However, the conventional methods as described above increase the charge / discharge capacity and increase the energy density, but the cycle performance is insufficient and the required characteristics of the market are still insufficient, which is not always satisfactory. However, further improvement in energy density has been desired.

In particular, in the method described in Patent Document 4, silicon oxide is used as a negative electrode material for a lithium ion secondary battery, and a high-capacity electrode is obtained. There is room for improvement because the irreversible capacity is large and the cycle performance has not reached the practical level.
In addition, regarding the technique for imparting conductivity to the negative electrode material, the method described in Patent Document 6 is a solid-solid fusion, so a uniform carbon film is not formed, and the conductivity is insufficient. There's a problem. In the method described in Patent Document 7, although a uniform carbon film can be formed, since Si is used as a negative electrode material, the expansion / contraction at the time of adsorption / desorption of lithium ions is too large. As such, there is a problem in that it cannot be put into practical use and the chargeability must be limited in order to prevent this because the cycle performance deteriorates.
Furthermore, in the method described in Patent Document 8, although the improvement in cycleability is confirmed due to insufficient precipitation of fine silicon crystals, the structure of the carbon coating and the fusion with the base material, When the number of cycles is repeated, there is a phenomenon that the capacity gradually decreases and then rapidly decreases after a certain number of times, which is still insufficient for a secondary battery.
Further, the above-described conventional negative electrode materials have many problems that the rate characteristics are still insufficient, and none of the cycle characteristic tray and the characteristics are satisfied.

JP-A-5-174818 JP-A-6-60867 JP 10-294112 A Japanese Patent No. 2999741 JP-A-11-102705 JP 2000-243396 A JP 2000-215887 A JP 2002-42806 A

  The present invention has been made in view of the above circumstances, and a negative electrode material for a non-aqueous electrolyte secondary battery that enables production of a negative electrode of a lithium ion secondary battery having higher cycle characteristics and rate characteristics than the conventional one, and a method for manufacturing the same, and An object is to provide a lithium ion secondary battery and an electrochemical capacitor.

In order to solve the above-described problems, the present invention provides a negative electrode material for a secondary battery using a nonaqueous electrolyte, and at least silicon oxide represented by the general formula SiO _x (x = 0.5 to 1.6). Any of a silicon composite having a structure in which silicon is dispersed in silicon dioxide and having a Si / O molar ratio of 1 / 0.5 to 1.6, and a mixture of the silicon oxide and the silicon composite, Provided is a negative electrode material for a non-aqueous electrolyte secondary battery characterized in that an element other than oxygen is contained at a concentration of 50 to 100,000 ppm.

Thus, the silicon oxide represented by the general formula SiO _x (x = 0.5 to 1.6) and the Si / O molar ratio having a structure in which silicon is dispersed in silicon dioxide are 1 / 0.5 to 1 .6, and a mixture of the silicon oxide and the silicon composite contains an element other than silicon and oxygen at a concentration of 50 to 100000 ppm. If present, the conductivity in the bulk is improved, thereby improving the rate characteristics and cycle characteristics when used as a negative electrode. Therefore, it becomes a negative electrode material suitable for a negative electrode for a secondary battery using a nonaqueous electrolyte that is superior in rate characteristics and cycle characteristics as compared with the conventional one.

Here, elements other than silicon and oxygen are La, V, Co, Mn, Ga, Ge, Sn, B, Al, Fe, Mg, Pb, Ag, As, Bi, Br, Cr, Hg, S, It is preferable that at least one of Te, P, and Nb is used.
Thus, if elements other than silicon and oxygen are elements as described above, the conductivity in the bulk can be further improved, and a negative electrode material having more excellent rate characteristics and cycle characteristics can be obtained.

Moreover, it is preferable that the negative electrode material for a non-aqueous electrolyte secondary battery has a volume average value D50 of 0.01 to _{50 [} mu] m by a laser diffraction / scattering particle size distribution measurement method.
As the negative electrode material for non-aqueous electrolyte secondary battery, by the D ₅₀ of the more than 0.01 [mu] m, it can prevent the bulk density of the negative electrode material obtained is too small, a high packing density in electrode formation can do. Further, it is possible to avoid the possibility that the purity is lowered due to the effect of surface oxidation, and it is possible to increase the charge / discharge capacity per unit volume. And by making D50 into ₅₀ micrometers or less, formation of an electrode does not become difficult and the possibility of peeling from a collector can be made sufficiently low.

And it is preferable that the negative electrode material for a non-aqueous electrolyte secondary battery further has a surface coated with a carbon film.
Thus, the negative electrode material for a non-aqueous electrolyte secondary battery in which the carbon coating is further coated on the surface has a good surface conductivity, so that the non-aqueous electrolyte secondary battery further excellent in cycle characteristics can be obtained. It becomes a negative electrode material suitable for the negative electrode.

And in this invention, it is a lithium ion secondary battery which consists of a positive electrode, a negative electrode, and a lithium ion conductive nonaqueous electrolyte, Comprising: The said negative electrode is used for the nonaqueous electrolyte secondary battery as described in this invention Provided is a lithium ion secondary battery using a negative electrode material.
As described above, the negative electrode material for a non-aqueous electrolyte secondary battery according to the present invention can improve battery characteristics (rate characteristics, cycle characteristics) when used as a negative electrode for a non-aqueous electrolyte secondary battery. is there. For this reason, the lithium ion secondary battery using the negative electrode material for a nonaqueous electrolyte secondary battery of the present invention has excellent battery characteristics, particularly rate characteristics and cycle characteristics.

Further, in the present invention, an electrochemical capacitor comprising at least a positive electrode, a negative electrode, and a conductive electrolyte, wherein the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention is used for the negative electrode. An electrochemical capacitor is provided.
Thus, the electrochemical capacitor using the negative electrode material for a non-aqueous electrolyte secondary battery of the present invention is also excellent in characteristics (rate characteristics and cycle characteristics) as a capacitor, like the above-described lithium ion secondary battery. It will be a thing.

Further, in the present invention, there is provided a method for producing a negative electrode material for a secondary battery using a nonaqueous electrolyte, wherein at least an element other than silicon and oxygen is contained in a silicon raw material, and the element other than silicon and oxygen is contained. Using a silicon raw material, the silicon oxide represented by the general formula SiO _x (x = 0.5 to 1.6) and the Si / O molar ratio having a structure in which silicon is dispersed in silicon dioxide have a molar ratio of 1 / 0.0. Any one of the silicon composite of 5 to 1.6 and the mixture of the silicon oxide and the silicon composite is prepared so that elements other than the silicon and oxygen are contained at a concentration of 50 to 100,000 ppm. A method for producing a negative electrode material for a non-aqueous electrolyte secondary battery is provided.

Thus, Si having a structure in which silicon oxide, silicon represented by the general formula SiO _x (x = 0.5 to 1.6), silicon is dispersed in silicon dioxide, from a silicon raw material containing elements other than silicon and oxygen. The concentration of elements other than silicon and oxygen is 50 to 100000 ppm in any of the silicon composite having a / O molar ratio of 1 / 0.5 to 1.6 and the mixture of the silicon oxide and the silicon composite. The bulk conductivity of the negative electrode material can be improved, and rate characteristics and cycle characteristics can be improved when the negative electrode is manufactured. Therefore, a negative electrode material suitable for a negative electrode for a non-aqueous electrolyte secondary battery, which is excellent in rate characteristics and cycle characteristics as compared with conventional ones, can be produced.

Here, the elements other than silicon and oxygen are La, V, Co, Mn, Ga, Ge, Sn, B, Al, Fe, Mg, Pb, Ag, As, Bi, Br, Cr, Hg, S, Preferably, at least one of Te, P, and Nb is used.
Thus, by manufacturing the negative electrode material such that the above-described elements other than silicon and oxygen are contained at a concentration of 50 to 100,000 ppm, the conductivity of the manufactured negative electrode material can be further improved. Therefore, a negative electrode material suitable for a negative electrode for a non-aqueous electrolyte secondary battery that is further excellent in rate characteristics and cycle characteristics can be produced.

Furthermore, it is preferable to coat the surface with a carbon film by chemical vapor deposition in an organic gas.
Thus, by further covering the surface with a carbon coating, the surface becomes a negative electrode material with good conductivity, and further becomes a negative electrode material suitable for the negative electrode of a non-aqueous electrolyte secondary battery with excellent cycle characteristics.

As described above, by using the negative electrode material for non-aqueous electrolyte secondary batteries obtained in the present invention as a negative electrode material for lithium ion secondary batteries or a negative electrode material for electrochemical capacitors, it has excellent rate characteristics and cycle characteristics. A lithium ion secondary battery or an electrochemical capacitor can be obtained.
In addition, the manufacturing method of the negative electrode material itself for non-aqueous electrolyte secondary batteries is simple and can sufficiently withstand industrial scale production, and contributes greatly to obtaining high-quality and inexpensive non-aqueous electrolyte secondary batteries. It has become something that can be done.

It is the figure which showed the outline of the manufacturing apparatus of the silicon oxide powder used in Example 1-3 and Comparative Example 1-2 of this invention.

Hereinafter, the present invention will be described more specifically.
First, the negative electrode material for a nonaqueous electrolyte secondary battery of the present invention will be described.
The negative electrode material for a non-aqueous electrolyte secondary battery of the present invention is composed of silicon oxide represented by the general formula SiO _x (x = 0.5 to 1.6), Si / O having a structure in which silicon is dispersed in silicon dioxide. Any of a silicon composite having a molar ratio of 1 / 0.5 to 1.6 and a mixture of the above silicon oxide and the above silicon composite contains an element other than silicon and oxygen at a concentration of 50 to 100,000 ppm. It is what.

In such a negative electrode material for a non-aqueous electrolyte secondary battery, elements other than silicon and oxygen are contained at a concentration of 50 to 100,000 ppm, so that the bulk conductivity is improved as compared with the conventional negative electrode material. Thus, when used as a negative electrode, the rate characteristics and cycle characteristics of the battery can be improved.
The molar ratio of Si / O having a structure in which silicon oxide represented by the general formula SiO _x (x = 0.5 to 1.6) and silicon are dispersed in silicon dioxide is 1 / 0.5 to 1.6. And a mixture of the above-mentioned silicon oxide and the above-mentioned silicon composite, which is superior in charge / discharge efficiency and cycle characteristics than the conventional negative electrode material.
Due to these effects, a negative electrode material for a non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics as compared with the conventional one can be obtained.

Here, silicon oxide in the present invention is a general term for amorphous silicon oxide obtained by cooling and precipitating silicon monoxide gas generated by heating a mixture of silicon dioxide and metal silicon. Yes, it is represented by the general formula SiO _x (x = 0.5 to 1.6).

  The silicon composite in the present invention refers to a silicon composite having a Si / O molar ratio of 1 / 0.5 to 1.6 and having a structure in which silicon is dispersed in silicon dioxide.

Note that the molar ratio of x in the silicon oxide and O in the silicon composite to Si is 0.5 to 1.6. This molar ratio is desirably 0.5 to 1.3, and more desirably 0.5 to 1.0.
It is technically difficult to produce a silicon oxide or silicon composite having a molar ratio of less than 0.5. Further, in the case of silicon oxide or silicon composite larger than 1.6, the ratio of inactive SiO ₂ is large during the heat treatment in the production process, and the charge / discharge capacity may decrease when used as a lithium ion secondary battery. is there. For this reason, the molar ratio of x in the silicon oxide and O in the silicon composite to Si is 0.5 to 1.6.

  Here, when the silicon composite was evaluated for a diffraction peak attributed to Si (111) centered around 2θ = 28.4 ° in X-ray diffraction (Cu-Kα) using copper as a counter cathode In addition, it is desirable that the following conditions (i) and (ii) are satisfied.

(I): In X-ray diffraction (Cu-Kα) using copper as a cathode, a diffraction peak attributed to Si (111) centered around 2θ = 28.4 ° is observed, and the broadening of the diffraction line It is desirable that the particle diameter of the silicon crystal in the silicon composite obtained from Scherrer's equation is 1 to 500 nm (preferably 2 to 200 nm, more preferably 2 to 50 nm).
By setting the size of the fine particles in the silicon composite to 1 nm or more, it is possible to reduce the risk of reducing the charge / discharge capacity as much as possible. Moreover, by setting it as 500 nm or less, the expansion / contraction at the time of charging / discharging becomes large, and a possibility that cycling property may fall can be prevented. The size of the silicon fine particles can be measured by a transmission electron micrograph.

(Ii): In solid-state NMR ( ²⁹ Si-DDMAS) measurement, the spectrum has a broad silicon dioxide peak centered around −110 ppm and a peak characteristic of Si diamond crystals in the vicinity of −84 ppm Is desirable. This spectrum is completely different from ordinary silicon oxide (SiO _x : x = 1.0 + α), and the structure itself is clearly different.
Further, it is confirmed by transmission electron microscope that silicon crystals are dispersed in amorphous silicon dioxide.

The mixture of silicon oxide and silicon composite is a mixture of the above-described silicon oxide powder and the above-mentioned silicon composite powder in a predetermined ratio.
The mixing ratio and mixing method of this mixture are not particularly limited, and can be appropriately selected so as to have desired physical properties.

Here, elements other than silicon and oxygen described above are La, V, Co, Mn, Ga, Ge, Sn, B, Al, Fe, Mg, Pb, Ag, As, Bi, Br, Cr, Hg, and S. , Te, P, and Nb.
Thus, if the above elements are contained at a concentration of 50 to 100,000 ppm as elements other than silicon and oxygen, the bulk conductivity in the negative electrode material can be further improved. Therefore, the negative electrode material is more excellent in rate characteristics and cycle characteristics.

In addition, the negative electrode material for a non-aqueous electrolyte secondary battery, which is the silicon oxide, the silicon composite, or a mixture thereof, has a volume average value D ₅₀ (that is, a cumulative volume of 50% by a laser diffraction scattering type particle size distribution measuring method). (Time particle diameter or median diameter) may be 0.01 to 50 μm.
By making D ₅₀ 0.01 μm or more, the possibility of lowering the purity due to the effect of surface oxidation can be avoided as much as possible, and when used as a negative electrode material, the bulk density decreases and the unit volume per unit volume is reduced. The risk of a decrease in charge / discharge capacity can be reduced as much as possible.
Further, by the D ₅₀ is to 50μm or less, it is possible to minimize the risk of causing a short circuit through the negative electrode film, that no formation of the electrode becomes difficult, peeling from the current collector This possibility can be made sufficiently low.

And the negative electrode material for nonaqueous electrolyte secondary batteries of this invention can make the surface further coat | covered with the carbon film.
Thus, the negative electrode material for a non-aqueous electrolyte secondary battery in which a carbon film is further coated on the surface has better conductivity on the surface than the conventional material, and in particular, a negative electrode material with more excellent cycle characteristics. Can do.

Next, the manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries in this invention is demonstrated in detail.
First, an element other than silicon and oxygen is contained in the silicon raw material.
And using this silicon raw material containing elements other than silicon and oxygen, a structure in which silicon oxide and silicon represented by the general formula SiO _x (x = 0.5 to 1.6) are dispersed in silicon dioxide is used. One of the silicon composite having a Si / O molar ratio of 1 / 0.5 to 1.6 and the mixture of the silicon oxide and the silicon composite at a concentration of 50 to 100,000 ppm of elements other than silicon and oxygen Prepare to be contained.

First, the manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries made of silicon oxide of the present invention will be described in more detail.
Elements other than silicon and oxygen, preferably La, V, Co, Mn, Ga, Ge, Sn, B, Al, Fe, Mg, Pb, Ag, As, Bi, Br, Cr, Hg, S, Te, Silicon powder containing at least one of P and Nb and silicon dioxide (SiO ₂ ) powder are contained so that the molar ratio of silicon to silicon dioxide is 1: 1.
The contained raw material is reacted at 1200 to 1500 ° C. (preferably 1300 to 1500 ° C.) under a reduced pressure of 3000 Pa or less (preferably 0.1 to 100 Pa) to cool the generated SiO gas, and silicon oxide Precipitate as a solid. In the solid to be precipitated, elements other than the above-described silicon and oxygen are contained at a concentration of 50 to 100,000 ppm. In order to contain elements other than silicon and oxygen at a concentration of 50 to 100,000 ppm, for example, it is achieved by adjusting the element concentration other than silicon and oxygen in the silicon powder, but of course not limited thereto. .
Thereafter, the precipitate is recovered to obtain the silicon oxide of the present invention.

Here, the SiO gas can be efficiently generated by setting the degree of reduced pressure when the mixed raw materials are reacted to 3000 Pa or less.
Moreover, SiO gas can be efficiently generated by making reaction temperature into 1200 degreeC or more. And by setting it as 1500 degrees C or less, it can prevent reliably that the silicon | silicone in a raw material fuse | melts and a reactivity deteriorates or a furnace is damaged. However, the reaction time is not particularly limited, and is appropriately selected according to the amount of raw material charged.

At this time, if elements other than silicon and oxygen are mixed as a mixture without being contained in the silicon raw material, or are separately installed and contained, there is a high possibility that the deposited silicon oxide will not be doped well.
Specifically, it does not react only by melting and may remain in an unreacted raw material as a reaction residue, or may be deposited alone in a place different from silicon oxide. Therefore, it is previously contained in the silicon raw material.

Next, the silicon composite of the present invention is produced by using the above silicon oxide powder represented by the general formula SiO _x as a raw material at 900 to 1400 ° C. (preferably 1000 to 1400 in an atmosphere containing at least an organic gas and / or steam). C., more preferably from 1050 to 1300.degree. C., and even more preferably from 1100 to 1200.degree. C.) to obtain a composite of silicon and silicon dioxide.

Further, the above silicon oxide powder represented by the general formula SiO _x is preliminarily subjected to heat treatment at 900 to 1400 ° C. (preferably 1000 to 1400 ° C., more preferably 1100 to 1300 ° C.) in an inert gas atmosphere. It can also be obtained by leveling.

Furthermore, the above-described silicon oxide powder represented by the general formula SiO _x is subjected to chemical vapor deposition with an organic gas and / or vapor in a temperature range of 500 to 1200 ° C. (preferably 500 to 1000 ° C., more preferably 500 to 900 ° C.). It is also possible to obtain a disproportionated material by subjecting it to a heat treatment at 900 to 1400 ° C. (preferably 1000 to 1400 ° C., more preferably 1100 to 1300 ° C.) in an inert gas atmosphere. .

It can also be obtained by coating silicon fine particles with silicon dioxide by the sol-gel method, or sintering silicon fine powder solidified through fine silica such as fumed silica or precipitated silica and water.
In addition, it can also be obtained by heating silicon and its partial oxide or nitride (desirably ground to a particle size of 0.1 to 50 μm) at 800 to 1400 ° C. under an inert gas stream.

The mixture of silicon oxide and silicon composite is obtained by mixing the above-described silicon oxide and the above-described silicon composite at a predetermined ratio.
The mixing ratio and mixing method at this time are not particularly limited, and can be appropriately selected so as to achieve desired physical properties.

Here, the content of elements other than silicon and oxygen in the silicon oxide as described above, the silicon composite described above, and a mixture thereof is 50 to 100,000 ppm (preferably 500 to 10,000 ppm) in the particles. To.
If it is less than 50 ppm, the effect of improving the conductivity obtained by doping is difficult to obtain, and the cycle characteristics and rate characteristics become insufficient. Moreover, since content will become excessive when it exceeds 100000 ppm, there exists a possibility that the fall of a capacity | capacitance may be produced, and it shall produce so that elements other than silicon and oxygen may be contained with the density | concentration of 50-100,000 ppm.

Further, the surface of the above-described silicon oxide, the above-described silicon composite, and a mixture thereof can be coated with a carbon coating to impart conductivity.
As this coating method, a method of chemical vapor deposition (CVD) of particles in an organic gas is suitable, and it can be efficiently performed by introducing an organic gas into the reactor during heat treatment.

For example, the above-described silicon oxide, the above-described silicon composite, and a mixture thereof can be obtained by chemical vapor deposition in an organic gas under a reduced pressure of 30,000 Pa or less. The pressure is preferably 10,000 Pa or less, more preferably about 2,000 Pa. The chemical vapor deposition temperature is more preferably 800 to 1,200 ° C, particularly 900 to 1,100 ° C.
The treatment time is appropriately selected depending on the target carbon coating amount, treatment temperature, organic gas concentration (flow rate), introduction amount, etc., but usually 1 to 10 hours, particularly about 2 to 7 hours is economical. Is also efficient.

If the degree of vacuum is 30,000 Pa or less, the ratio of the graphite material having a graphite structure becomes too large, and when used as a negative electrode material for a lithium ion secondary battery, the cycle performance is reduced in addition to the reduction in battery capacity. You can prevent the risk of doing.
Further, by setting the treatment temperature to 800 ° C. or higher, it is not necessary to perform a long-time treatment, and the productivity can be increased. By setting the temperature to 1,200 ° C. or lower, the possibility of particles fusing and agglomerating by chemical vapor deposition can be reliably suppressed, and a conductive coating is not formed on the agglomerated surface, and for non-aqueous electrolyte secondary batteries. When used as a negative electrode material, it is possible to reliably prevent a situation in which the cycle performance is not improved.

The organic material used as a raw material for generating the organic gas in the present invention is preferably selected from those that can be pyrolyzed at the above heat treatment temperature to produce carbon (graphite), particularly in a non-acidic atmosphere.
For example, hydrocarbons such as methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane, etc., alone or as a mixture, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, Examples thereof include monocyclic to tricyclic aromatic hydrocarbons such as chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, and mixtures thereof.
Further, gas light oil, creosote oil, anthracene oil, and naphtha cracked tar oil obtained in the tar distillation step can be used alone or as a mixture.

The amount of the carbon coating is not particularly limited, but is preferably 0.3 to 40% by mass with respect to the total of the above-described silicon oxide coated with carbon, the above-described silicon composite, and a mixture thereof. Is preferably 0.5 to 30% by mass.
By setting the coating amount of the carbon coating to 0.3% by mass or more, sufficient conductivity can be maintained, and when the negative electrode material for a non-aqueous electrolyte secondary battery is obtained, the cycle characteristics can be further improved. it can. In addition, by setting the coating amount of the carbon coating to 40% by mass or less, it is possible to prevent the proportion of carbon in the negative electrode material from becoming too large, and thus more reliably prevent the charge / discharge capacity from being lowered. it can.

  And the negative electrode can be produced using the nonaqueous electrolyte secondary battery negative electrode material obtained by this invention as an active material, and a lithium ion secondary battery and an electrochemical capacitor can be manufactured.

In addition, when producing a negative electrode using the said negative electrode material for nonaqueous electrolyte secondary batteries, electrically conductive agents, such as carbon and graphite, can be added.
Also in this case, the kind of the conductive agent is not particularly limited, and any electronic conductive material that does not cause decomposition or alteration in the configured battery may be used. Specifically, metal powder such as Al, Ti, Fe, Ni, Cu, Zn, Ag, Sn, Si, metal fiber, natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor grown carbon fiber, pitch Graphite such as carbon-based carbon fiber, PAN-based carbon fiber, and various resin fired bodies can be used.

Moreover, as a preparation method of a negative electrode (molded object), the following method is mentioned, for example.
N-methylpyrrolidone or water or other solvent is kneaded with the previously manufactured negative electrode material, a conductive agent, if necessary, and other additives such as a binder. The agent is applied to the current collector sheet. Thereafter, a negative electrode can be formed on the current collector by performing a process such as drying and pressing.
If this collector is a material normally used as a collector of a negative electrode, such as a copper foil or a nickel foil, it can be used without any particular limitation on thickness and surface treatment.
In addition, the shaping | molding method which shape | molds a mixture into a sheet form is not specifically limited, A well-known method can be used.

And a lithium ion secondary battery can be manufactured using the negative electrode material for nonaqueous electrolyte secondary batteries obtained by this invention.
In this case, the obtained lithium ion secondary battery is characterized in that the negative electrode material for a nonaqueous electrolyte secondary battery of the present invention is used, and other materials such as positive electrode, electrolyte, separator, and battery Known shapes and the like can be used and are not particularly limited.

For example, as the positive electrode active material, oxides of transition metals such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , lithium, chalcogen compounds, and the like are used.
As the electrolyte, for example, a non-aqueous solution containing a lithium salt such as lithium hexafluorophosphate and lithium perchlorate is used. As the non-aqueous solvent, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethoxyethane, γ-butyrolactone is used. , 2-methyltetrahydrofuran or the like can be used alone or in combination. Various other non-aqueous electrolytes and solid electrolytes can also be used.

  In the case of producing an electrochemical capacitor, the electrochemical capacitor is characterized in that the negative electrode material for a non-aqueous electrolyte secondary battery of the present invention is used, and other electrolytes, materials such as separators, capacitor shapes, etc. Is not limited.

  For example, non-aqueous solutions containing lithium salts such as lithium hexafluorophosphate, lithium perchlorate, lithium borofluoride, lithium hexafluoroarsenate, etc. are used as the electrolyte, and propylene carbonate, ethylene carbonate, dimethyl carbonate are used as the non-aqueous solvent. , Diethyl carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran, or the like, or a combination of two or more types. 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 more concretely, this invention is not limited to these.
Example 1
2 kg of polycrystalline Si for semiconductor production and 60 g of metal Mn powder were charged into a crucible and melted by heating at 1450 ° C. for 3 hours in an Ar atmosphere using a high-temperature atmosphere furnace.
After cooling, it was taken out from the crucible, coarsely crushed with a jaw crusher, and then pulverized with a ball mill to obtain an alloy powder having an average particle size of 5 μm.
1 kg of this alloy powder and 2 kg of silicon dioxide powder (BET specific surface area 200 m ² / g) were kneaded by adding 3 kg of pure water, and then dried to obtain a silicon oxide production raw material.

Next, silicon oxide was produced. An apparatus as shown in FIG. 1 was used for producing this silicon oxide.
In an apparatus as shown in FIG. 1, 100 g of the silicon oxide production raw material 5 was charged in a sample container 4, placed in an alumina furnace core tube 1, and the inside of the furnace core tube 1 was decompressed using a vacuum pump 7.
Then, after confirming that the pressure inside the furnace reached 100 Pa with the pressure gauge 8, the heater 2 was energized, heated to a temperature of 1,400 ° C., and maintained for 5 hours in a state where silicon monoxide vapor was generated. The generated silicon monoxide vapor was deposited on a SUS deposition base 6. At this time, the temperature control of the precipitation base 6 was performed by two systems of the thickness of the heat insulating material 3 and forced cooling.
As a result, the pressure inside the furnace core tube 1 was finally reduced to 30 Pa. Moreover, the reaction rate calculated | required from the reaction residual weight of the raw material was 93.8%. Then, 72 g of silicon oxide deposited on the substrate 6 could be recovered.

The obtained precipitate was pulverized with a raikai machine and then subjected to elemental analysis with an ICP emission spectroscopic analyzer.
As a result, the Mn content was 1% by mass (10000 ppm).

This precipitate was pulverized with a ball mill for 5 hours to obtain a Mn-doped silicon oxide powder having an average particle diameter of 4.5 μm and a BET specific surface area of 5.6 m ² / g.
This powder was analyzed with an X-ray diffractometer (Bruker AXS D8 ADVANCE). As a result, in the X-ray diffraction (Cu-Kα) using copper as the counter cathode, the diffraction peak attributed to Si (111) centered around 2θ = 28.4 ° was used, and the value was obtained by the Scherrer equation. The particle size of the silicon crystals was 2 nm. Further, a structure in which silicon nanoparticles were dispersed in silicon oxide was confirmed by a transmission electron microscope.

Next, 50 g of this powder was charged into a batch type heating furnace.
Specifically, the inside of the furnace is heated to 1100 ° C. while the inside of the furnace is depressurized with an oil rotary vacuum pump, and after reaching 1100 ° C., CH ₄ gas is introduced at 0.3 NL / min, and carbon coating is performed for 5 hours. Processed. In addition, the pressure reduction degree at this time was 800 Pa.
After the treatment, the temperature was lowered to obtain about 52.7 g of black powder. The obtained black powder was a conductive powder having an average particle diameter of 5.2 μm and a carbon coating amount of 5 mass% with respect to the black powder.
The particle diameter of the silicon crystal determined by the Scherrer equation using the X-ray diffraction peak of this powder was 5 nm. Further, a structure in which silicon nanoparticles were dispersed in silicon oxide was confirmed by a transmission electron microscope.

<Battery evaluation>
Next, battery evaluation using the obtained conductive powder as a negative electrode active material was performed by the following method.
First, 10 g of polyimide was added to 90 g of the obtained conductive powder, and further N-methylpyrrolidone was added to form a slurry. This slurry was applied to a copper foil having a thickness of 20 μm, dried at 80 ° C. for 1 hour, and then by a roller press. The electrode was pressure-molded, and this electrode was vacuum-dried at 350 ° C. for 1 hour, then punched out to 2 cm ² to obtain a negative electrode.

  Here, in order to evaluate the charge / discharge characteristics of the obtained negative electrode, a lithium foil was used as a counter electrode, and lithium hexafluoride was mixed with 1/1 (volume ratio) of ethylene carbonate and diethyl carbonate as a non-aqueous electrolyte. A lithium ion secondary battery for evaluation using a non-aqueous electrolyte solution dissolved at a concentration of 1 mol / L and a polyethylene microporous film having a thickness of 30 μm as a separator was prepared.

The prepared lithium ion secondary battery for evaluation was allowed to stand overnight at room temperature, and then charged with a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.) until the test cell voltage reached 0 V at 0.5 mA / cm. ^The battery was charged with a constant current of ² , and after reaching 0V, the battery was charged by decreasing the current so as to keep the cell voltage at 0V. Then, the charging was terminated when the current value fell below 40 μA / cm ² . Discharging was performed at a constant current of 0.5 mA / cm ² , discharging was terminated when the cell voltage exceeded 2.0 V, and the discharge capacity was determined.
The above charge / discharge test was repeated, and a charge / discharge test after 200 cycles of the evaluation lithium ion secondary battery was performed. The results are shown in Table 1.
Moreover, discharge was performed at two discharge rates of 0.2c and 1.0c, and the discharge capacity at the time of 1.0c discharge divided by the discharge capacity at the time of 0.2c discharge was measured to evaluate the rate characteristics. The results are also shown in Table 1.

(Example 2)
2 kg of polycrystalline Si for semiconductor production and 60 g of metal Ga powder of the same grade as those used in Example 1 were charged in a crucible and heated and melted at 1450 ° C. for 3 hours in an Ar atmosphere using a high-temperature atmosphere furnace.
After cooling, it was taken out from the crucible, coarsely crushed with a jaw crusher, and then pulverized with a ball mill to obtain an alloy powder having an average particle size of 5 μm.
Using this alloy powder, silicon oxide was produced using an apparatus as shown in FIG. The reaction rate at this time was 92.9%.

The obtained precipitate was pulverized with a raikai machine and then subjected to elemental analysis with an ICP emission spectroscopic analyzer.
As a result, the Ga content was 1% by mass (10000 ppm).

This precipitate was pulverized with a ball mill for 5 hours to obtain a Ga-doped silicon oxide powder having an average particle size of 4.7 μm and a BET specific surface area of 4.8 m ² / g.

This powder was subjected to a carbon coating treatment in the same manner as in Example 1 to obtain a black conductive powder having an average particle diameter of 5.0 μm and a carbon coating amount of 5 mass% with respect to the powder.
As a result of analyzing this powder with an X-ray diffractometer in the same manner as in Example 1, the particle diameter of the silicon crystals was 5 nm.

  And the evaluation lithium ion secondary battery was produced on the conditions similar to Example 1, and the same evaluation was performed. The results are shown in Table 1.

(Example 3)
2 kg of polycrystalline Si for semiconductor production and 60 g of metal Sn powder of the same grade as those used in Example 1 were charged in a crucible and heated and melted at 1450 ° C. for 3 hours in an Ar atmosphere using a high-temperature atmosphere furnace.
After cooling, it was taken out from the crucible, coarsely crushed with a jaw crusher, and then pulverized with a ball mill to obtain an alloy powder having an average particle size of 5.1 μm.
Using this alloy powder, silicon oxide was produced using an apparatus as shown in FIG. The reaction rate at this time was 94.0%.

The obtained precipitate was pulverized with a raikai machine and then subjected to elemental analysis with an ICP emission spectroscopic analyzer.
As a result, the Sn content was 4000 ppm.

This precipitate was pulverized with a ball mill for 5 hours to obtain a Sn-containing powder having an average particle diameter of 5.0 μm and a BET specific surface area of 5.1 m ² / g.

This powder was subjected to a carbon coating treatment in the same manner as in Example 1 to obtain a black conductive powder having an average particle diameter of 5.0 μm and a carbon coating amount of 5 mass% with respect to the powder.
As a result of analyzing this powder with an X-ray diffractometer in the same manner as in Example 1, the particle diameter of the silicon crystals was 5 nm.

  And the evaluation lithium ion secondary battery was produced on the conditions similar to Example 1, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 1)
Using a powder as shown in FIG. 1 in the same manner as in Example 1 using a powder having an average particle size of 5 μm obtained by pulverizing 2 kg of polycrystalline Si for semiconductor production of the same grade as that used in Example 1 with a ball mill. Silicon oxide was produced. The reaction rate at this time was 95.5%.

  The precipitate was pulverized by a raikai machine and then subjected to elemental analysis using an ICP emission spectroscopic analyzer. As a result, the content of elements other than silicon and oxygen was less than 10 ppm.

This was pulverized with a ball mill for 5 hours to obtain a powder having an average particle diameter of 5.0 μm and a BET specific surface area of 5.1 m ² / g.

This powder was subjected to a carbon coating treatment in the same manner as in Example 1 to obtain a black conductive powder having an average particle diameter of 5.0 μm and a carbon coating amount of 5 mass% with respect to the powder.
As a result of analyzing this powder with an X-ray diffractometer in the same manner as in Example 1, the particle diameter of the silicon crystals was 5 nm.

  And the evaluation lithium ion secondary battery was produced on the conditions similar to Example 1, and the same evaluation was performed. The results are shown in Table 1.

(Comparative Example 2)
Polycrystalline Si for semiconductor production of the same grade as used in Example 1 was pulverized with a ball mill to give an average particle size of 5 μm, 30 g of metal Mn powder, 0.9 g of silicon dioxide powder (BET specific surface area of 200 m ² / g) 100 g of pure water was added to 64 g and kneaded and dried.
This kneaded and dried powder was charged into a crucible, and silicon oxide was produced using an apparatus as shown in FIG. At the time of collecting the precipitate, a metallic substance was deposited at a place different from silicon oxide, and the reaction rate was as low as 57.4%.

The precipitate was pulverized with a lykai machine and then pulverized with a ball mill for 5 hours to obtain a black conductive powder having an average particle diameter of 5.1 μm and a BET specific surface area of 5.2 m ² / g.
As a result of elemental analysis using an ICP emission spectroscopic analyzer, this powder was found to have a Mn content of 35 ppm.

  And the evaluation lithium ion secondary battery was produced on the conditions similar to Example 1, and the same evaluation was performed. The results are shown in Table 1.

As shown in Table 1, it was confirmed that the powder of Example 1 was a lithium ion secondary battery with a capacity retention rate of 88% after 200 cycles and excellent cycle characteristics. Moreover, the ratio of 1.0c / 0.2c was 90%, and it was confirmed that the rate characteristics were excellent.
In addition, the powder of Example 2 also had a capacity retention rate of 83% after 200 cycles and a ratio of 1.0c / 0.2c of 87%, and it was confirmed that the rate characteristics were excellent as in Example 1. It was.
The powder of Example 3 also had a capacity retention rate of 86% after 200 cycles and a ratio of 1.0c / 0.2c of 89%, and it was confirmed that the rate characteristics were excellent as in Examples 1 and 2. It was.

On the other hand, as shown in Table 1, it was found that the powder of Comparative Example 1 had a capacity retention rate of 73% after 200 cycles, which was clearly inferior to that of Example 1-3 and inferior in cycle characteristics. It was. Further, the ratio of 1.0c / 0.2c was 82%, and it was found that the rate characteristics were inferior.
And it turned out that the powder of the comparative example 2 is inferior in cycle characteristics compared with Example 1-3 like the powder of the comparative example 1 with the capacity | capacitance maintenance factor 75% after 200 cycles. The ratio of 1.0c / 0.2c was 83%, indicating that the rate characteristics were inferior.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  DESCRIPTION OF SYMBOLS 1 ... Furnace core tube, 2 ... Heater, 3 ... Thermal insulation material, 4 ... Sample container, 5 ... Raw material, 6 ... Precipitation base, 7 ... Vacuum pump, 8 ... Pressure gauge.

Claims (3)

A method for producing a negative electrode material for a secondary battery using a non-aqueous electrolyte,
At least the silicon raw material contains elements other than silicon and oxygen,
Using silicon raw materials containing elements other than silicon and oxygen, silicon oxide represented by the general formula SiO _x (x = 0.5 to 1.6), Si having a structure in which silicon is dispersed in silicon dioxide Any of a silicon composite having a / O molar ratio of 1 / 0.5 to 1.6 and a mixture of the silicon oxide and the silicon composite is contained at a concentration of 50 to 100,000 ppm of elements other than the silicon and oxygen. A method for producing a negative electrode material for a nonaqueous electrolyte secondary battery, wherein the negative electrode material is produced so as to be contained.   Elements other than silicon and oxygen are La, V, Co, Mn, Ga, Ge, Sn, B, Al, Fe, Mg, Pb, Ag, As, Bi, Br, Cr, Hg, S, Te, P. The method for producing a negative electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein at least one of Nb and Nb is used.   Furthermore, the surface is coat | covered with a carbon film by carrying out chemical vapor deposition in organic substance gas, The manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries of Claim 1 or Claim 2 characterized by the above-mentioned.

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