JP2011142021A - Silicon oxide for nonaqueous electrolyte secondary battery anode material, method of manufacturing silicon oxide for nonaqueous electrolyte secondary battery anode material, lithium ion secondary battery, and electrochemical capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing silicon oxide as an active material effective as an anode material for a nonaqueous electrolyte secondary battery with high initial charge and discharge efficiency and excellent cycle characteristics with high battery capacity and a low volume expansion rate maintained. <P>SOLUTION: In the method of manufacturing silicon oxide used as an anode material for a secondary battery using nonaqueous electrolyte, at least a raw material generating SiO gas is heated under existence of inert gas or under reduced pressure within a temperature range of 1,100 to 1,600°C to generate SiO gas, and reducing gas is supplied to the SiO gas generated for reaction, and then, a reactant obtained by the reaction is collected in the method of manufacturing the silicon oxide for a nonaqueous electrolyte secondary battery. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a silicon oxide that can be used as a negative electrode material for a non-aqueous electrolyte secondary battery that exhibits high initial charge / discharge efficiency and good cycle characteristics when used as a negative electrode active material for lithium ion secondary batteries and electrochemical capacitors. The present invention relates to a product, a manufacturing method thereof, and a lithium ion secondary battery and an electrochemical capacitor in which the product is used as a negative electrode material.

In recent years, with the remarkable development of portable electronic devices, communication devices, etc., there is a strong demand for non-aqueous electrolyte secondary batteries with high energy density from the viewpoints of economy and downsizing and weight reduction of devices.
Conventionally, as a measure for increasing the capacity of this type of non-aqueous electrolyte secondary battery, for example, negative electrode materials such as oxides such as B, Ti, V, Mn, Co, Fe, Ni, Cr, Nb, and Mo and composites thereof A method using an oxide (see Patent Documents 1 and 2, etc.), and a method in which M _100-x Si _x (x ≧ 50 at%, M = Ni, Fe, Co, Mn) that has been melt-quenched and cooled is applied as a negative electrode material (Patent Documents) 3), a method using an oxide of silicon as a negative electrode material (see Patent Document 4), a method using Si ₂ N ₂ O, Ge ₂ N ₂ O and Sn ₂ N ₂ O as a negative electrode material (Patent Document 5). Etc.) are known.

Among these, silicon oxide can be expressed as SiO _x (where x is slightly larger than the theoretical value 1 because of the oxide film), but in the analysis by X-ray diffraction, amorphous silicon of about several nm to several tens of nm is used. Is finely dispersed in silica.
For this reason, although the battery capacity is small compared to silicon, it is considered to be easy to use as a negative electrode active material because it is 5 to 6 times higher per weight than carbon and further has a small volume expansion.

  However, since silicon oxide has a large irreversible capacity and an initial efficiency as low as about 70%, when actually manufacturing a battery, the battery capacity of the positive electrode is excessively required, and the capacity is 5 to 6 times per active material. We could not expect an increase in battery capacity to meet the increase.

Thus, the practical problem of silicon oxide is that the initial efficiency is remarkably low, and means for solving this include, for example, a method of replenishing the irreversible capacity and a method of suppressing the irreversible capacity.
For example, it has been reported that a method of compensating for the irreversible capacity by doping Li metal in advance is effective. Specifically, there are a method of attaching a Li foil to the surface of the negative electrode active material in order to dope Li metal (see Patent Document 6 and the like), a method of performing Li deposition on the surface of the negative electrode active material (see Patent Document 7 and the like), and the like. It is disclosed.
However, it is difficult to obtain a Li thin body suitable for the initial efficiency of the silicon oxide negative electrode by attaching the Li foil, and the cost is high. Further, the vapor deposition using Li vapor has a problem that the manufacturing process is complicated and is not practical.

On the other hand, a method for increasing the initial efficiency by increasing the mass ratio of Si irrespective of Li doping is disclosed.
One is a method in which silicon powder is added to silicon oxide powder to reduce the mass ratio of silicon oxide (see Patent Document 8, etc.), and the other is by simultaneously generating and depositing silicon vapor in the production stage of silicon oxide. This is a method of obtaining a mixed solid of silicon and silicon oxide (see Patent Document 9).
However, silicon has both high initial efficiency and battery capacity compared to silicon oxide, but is an active material that exhibits a volume expansion coefficient of 400% during charging, and even when added to a mixture of silicon oxide and carbon material. The volume expansion coefficient of silicon oxide cannot be maintained. Therefore, as a result, it was necessary to add 20% by mass or more of a carbon material to suppress the battery capacity to 1000 mAh / g. On the other hand, in the method of obtaining a mixed solid by simultaneously generating vapors of silicon and silicon oxide, since the vapor pressure of silicon is low, a manufacturing process at a high temperature exceeding 2000 ° C. is required, and there is a serious problem in work. .

Japanese Patent No. 3008228 Japanese Patent No. 3242751 Japanese Patent No. 3846661 Japanese Patent No. 2999741 Japanese Patent No. 3918311 Japanese Patent Laid-Open No. 11-086847 JP 2007-122992 A Japanese Patent No. 3982230 JP 2007-290919 A

As described above, even if the silicon-based active material is a single metal or an oxide thereof, each has a problem to be solved, which has been a problem in practical use.
Therefore, volume change associated with insertion and extraction of Li can be sufficiently suppressed, and it is possible to alleviate a decrease in conductivity due to pulverization due to particle cracking and peeling from the current collector, and mass production is possible. There has been a demand for a negative electrode active material that is advantageous in terms of cost and that can be applied to applications in which repeated cycle characteristics are particularly important, such as for mobile phones.

  The present invention has been made in view of the above-described problems, and maintains high battery capacity and low volume expansion coefficient of silicon oxide, and has high initial charge / discharge efficiency and excellent non-aqueous electrolyte secondary battery with excellent cycle characteristics. An object of the present invention is to provide a silicon oxide as an active material effective as a negative electrode material and a method for producing the same, and a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte secondary battery negative electrode using the silicon oxide. To do.

  In order to solve the above problems, in the present invention, a silicon oxide used for a negative electrode material for a secondary battery using a non-aqueous electrolyte, the silicon oxide having an oxygen content of 20 to 35 mass%, In addition, the present invention provides a silicon oxide for a negative electrode material for a non-aqueous electrolyte secondary battery, which is obtained by reacting SiO gas with a reducing gas.

As described above, the silicon oxide obtained by reacting the SiO gas and the reducing gas with an oxygen content of 20 to 35% by mass has a low oxygen content. Therefore, the non-aqueous electrolyte secondary battery, For example, when used as a negative electrode material for a lithium ion secondary battery, the reaction between oxygen and Li ions (irreversible formation of Li ₄ SiO ₄ ) is suppressed, and the first decrease in charge / discharge efficiency has been conventionally achieved. It will be suppressed in comparison. Therefore, it becomes a silicon oxide excellent in initial charge / discharge efficiency and cycle characteristics, and can be a negative electrode material having characteristics of silicon oxide such as high capacity and low volume expansion coefficient.
Further, since it is obtained by reacting SiO gas and reducing gas, the composition in silicon oxide is stable, and the composition is locally as in a mixture of silicon monoxide and silicon dioxide. There is no part that is not stable, and the cycle characteristics are excellent.

Here, the silicon oxide is preferably particles having an average particle diameter of 0.1 to 30 μm and a BET specific surface area of 0.5 to 30 m ² / g.
Thus, by making the average particle diameter of silicon oxide 0.1 μm or more, the bulk density can be prevented from becoming too small, and the charge / discharge capacity per unit volume can be prevented from decreasing. Further, when the average particle diameter is 30 μm or less, electrode formation is facilitated, and the possibility of peeling from the current collector (such as copper foil) can be minimized.
In addition, when the BET specific surface area of silicon oxide is 0.5 m ² / g or more, the surface activity can be increased, and the binding force of the binder during electrode production can be increased. Therefore, cycle characteristics when charging and discharging are repeated can be improved. And by setting it as 30 m < ² > / g or less, it can suppress that the amount of absorption of a solvent becomes large at the time of electrode preparation, and in order to maintain binding property, a large amount of binders are added, and the electroconductivity accompanying this is added. It is possible to prevent the possibility that the cycle characteristics are deteriorated due to the deterioration of the property.

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 at least, Comprising: The said negative electrode is a nonaqueous electrolyte secondary battery negative electrode as described in this invention Provided is a lithium ion secondary battery in which a silicon oxide for a material is used for a negative electrode material.
As described above, the silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material of the present invention has good battery characteristics (charge / discharge capacity, cycle characteristics) when used as a negative electrode for a non-aqueous electrolyte secondary battery. It is suitable for the negative electrode material for nonaqueous electrolyte secondary batteries. For this reason, the lithium ion secondary battery in which the silicon oxide for a nonaqueous electrolyte secondary battery negative electrode material of the present invention is used as a negative electrode material has excellent battery characteristics, particularly charge / discharge capacity and cycle characteristics.

The present invention is also an electrochemical capacitor comprising at least a positive electrode, a negative electrode, and a conductive electrolyte, wherein the silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material according to the present invention is formed on the negative electrode. Provided is an electrochemical capacitor used for a negative electrode material.
Thus, the electrochemical capacitor in which the silicon oxide for a negative electrode material of a non-aqueous electrolyte secondary battery of the present invention is used as a negative electrode material also has characteristics (charge / discharge capacity) as the above-described lithium ion secondary battery. And cycle characteristics).

  Furthermore, the present invention provides a method for producing a silicon oxide used for a negative electrode material for a secondary battery using a non-aqueous electrolyte, wherein at least a raw material that generates SiO gas is used in the presence of an inert gas or under reduced pressure. Then, heating is performed in a temperature range of 1,100 to 1,600 ° C. to generate SiO gas, and a reducing gas is supplied to the generated SiO gas to react, and the reaction product obtained by the reaction is recovered. A method for producing a silicon oxide for a negative electrode material for a non-aqueous electrolyte secondary battery is provided.

Thus, the reaction product (silicon oxide) is produced by reacting the reducing gas with the SiO gas generated by heating in the temperature range of 1,100 to 1,600 ° C. in the presence of an inert gas or under reduced pressure. The oxygen content in the silicon oxide particles represented by SiO _x having a high battery capacity and a low volume expansion coefficient can be reduced by recovering. That is, for example, when used as a negative electrode material of a lithium ion secondary battery, the generation of irreversible Li ₄ SiO ₄ is suppressed as compared with the conventional case, so that the first charge / discharge efficiency and the deterioration of cycle characteristics are suppressed as compared with the conventional case. The negative electrode material which consists of the made silicon oxide can be manufactured.
Therefore, for example, when used as a negative electrode material for a non-aqueous electrolyte secondary battery, it is possible to produce silicon oxide suitable for a negative electrode material having excellent initial charge / discharge efficiency and cycle characteristics. A non-aqueous electrolyte secondary battery having excellent properties can be obtained.

The reactant is preferably a silicon oxide having an oxygen content of 20 to 35% by mass.
Thus, if the reaction product is a silicon oxide having an oxygen content of 20 to 35% by mass, silicon oxide having excellent initial charge / discharge efficiency and cycle characteristics, high battery capacity, and low volume expansion coefficient. Thus, it is possible to produce a silicon oxide for a negative electrode of a non-aqueous electrolyte secondary battery that contributes to the production of a non-aqueous electrolyte secondary battery having higher capacity and excellent cycleability.

As the raw material, it is preferable to use either silicon oxide powder or a mixture of silicon dioxide powder and metal silicon powder.
Thus, if the raw material is either silicon oxide powder or a mixture of silicon dioxide powder and metal silicon powder, SiO gas can be generated efficiently. Therefore, by using such a powder or mixed powder as a raw material for generating SiO gas, a silicon oxide suitable for a negative electrode material for a non-aqueous electrolyte secondary battery with high productivity and high capacity and high cycle characteristics can be obtained. It can be manufactured and is useful for reducing manufacturing costs.

Further, the reducing gas contains hydrogen, carbon monoxide, a hydrocarbon gas represented by C _n H _4n (n = 1 to 3), any one of ammonia, or a mixed gas thereof. It is preferable to use it.
The above-described gases are all excellent in reducing power, and are suitable for reducing SiO gas. Further, almost no by-products are produced, which is advantageous in terms of cost.

As described above, the silicon oxide obtained in the present invention is used as a negative electrode material for a lithium ion secondary battery negative electrode material or an electrochemical capacitor, so that the initial charge / discharge efficiency is high and the high capacity / cycle characteristics are excellent. Lithium ion secondary batteries and electrochemical capacitors can be obtained.
Also, the silicon oxide production method can sufficiently withstand simple and industrial scale production, and an inexpensive non-aqueous electrolyte secondary battery can be obtained.

It is the figure which showed the outline of the horizontal tubular furnace used by manufacture of the silicon oxide for nonaqueous electrolyte secondary battery negative electrode materials of Example 1-4 and Comparative Example 1-2.

Hereinafter, the present invention will be described more specifically.
As described above, while maintaining a high battery capacity and low volume expansion coefficient of silicon oxide, an active material effective for a negative electrode of a non-aqueous electrolyte secondary battery having high initial charge / discharge efficiency and excellent cycle characteristics, and its production The development of the method was awaited.

  Therefore, the present inventors have reduced the initial charge / discharge efficiency, which is an active material that exceeds the battery capacity of the carbon material, suppresses the volume expansion change peculiar to the silicon-based negative electrode active material, and is a defect of silicon oxide. The silicon-based active material that improved the quality was studied earnestly.

As a result, when silicon oxide particles represented by SiO _x are used as the negative electrode active material, oxygen and Li ions in silicon oxide react to generate irreversible Li ₄ SiO _4. Turned out to be lower.
That is, it has been found that there is a high possibility that the above problem can be solved by reducing oxygen in silicon oxide.

Accordingly, as a result of further intensive studies on the method for reducing silicon oxide, the present inventors have found that silicon having a low oxygen content is relatively easily obtained by reducing the SiO gas with a reducing gas and recovering the reactant. It has been found that oxides can be produced efficiently.
Then, by using this silicon oxide as an active material for the negative electrode material, the initial charge / discharge efficiency can be improved, and the negative electrode for a non-aqueous electrolyte secondary battery of a high capacity and excellent cycle performance It has been found that a material can be obtained, and has led to the present invention.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
The silicon oxide used for the negative electrode material for a secondary battery using the nonaqueous electrolyte of the present invention is obtained by reacting SiO gas with a reducing gas, and the oxygen content thereof is 20 to 20%. 35% by mass. The oxygen content is more desirably 23 to 33% by mass, and further desirably 25 to 32% by mass.

When the oxygen content is less than 20% by mass, the initial efficiency and the battery capacity are improved when used as a negative electrode material for a non-aqueous electrolyte secondary battery, but the composition is close to that of silicon and the cycle characteristics are improved. There is a problem that it falls. On the other hand, if the amount is more than 35% by mass, there is a problem that the initial efficiency and the battery capacity cannot be improved. For this reason, oxygen content shall be 20-35 mass%.
And silicon oxide which is not obtained by reacting SiO gas and reducing gas (for example, silicon monoxide powder and silicon powder were mixed so that the total oxygen content was 20 to 35% by mass) A negative electrode material using silicon oxide is inferior in cycle characteristics when used as a secondary battery. Accordingly, the silicon oxide in the present invention is obtained by reacting SiO gas and reducing gas.

Thus, since the silicon oxide of the present invention has a low oxygen content, for example, when used as a negative electrode material for a lithium ion secondary battery, irreversible production of Li ₄ SiO ₄ was suppressed compared to the conventional case. It will be a thing. For this reason, the first decline in charge / discharge efficiency is suppressed as compared with the conventional case. In addition, because it is obtained by reacting SiO gas and reducing gas, the composition in the silicon oxide is locally stable, without being inferior in cycle characteristics, Is something that can be done.
That is, it is a silicon oxide excellent in initial charge / discharge efficiency and cycle characteristics, which also has the characteristics of silicon oxide such as high capacity and low volume expansion coefficient, and can be a high-quality negative electrode material.

  Here, the oxygen content of silicon oxide can be measured, for example, by a metal oxygen analysis method (inert gas melting furnace oxygen analysis method). As a specific example of the measuring apparatus, EMGA-920 manufactured by Horiba, Ltd. Etc.

The silicon oxide in the present invention has an oxygen content of 20 to 35% by mass, and the physical properties other than those obtained by reacting SiO gas and reducing gas are not particularly limited. However, the average particle size is preferably 0.1 to 30 μm, particularly preferably 0.2 to 20 μm. The BET specific surface area is preferably 0.5 to 30 m ² / g, particularly 1 to 20 m ² / g.
In addition, the average particle diameter in this invention is a particle diameter (median diameter) when a cumulative weight will be 50% in the particle size distribution measurement by a laser beam diffraction method.
Further, the BET specific surface area in the present invention is a value when measured by the BET one-point method evaluated by the N ₂ gas adsorption amount.

Thus, when the average particle diameter of the silicon oxide is 0.1 μm or more, the specific surface area is increased, and the proportion of silicon dioxide on the particle surface is increased, and the accompanying nonaqueous electrolyte secondary battery negative electrode material It can suppress that a battery capacity falls when using as. Moreover, it is prevented that a bulk density becomes small too much and it can also prevent that the charging / discharging capacity per unit volume falls. Furthermore, the manufacture and formation of the negative electrode are facilitated.
In addition, by setting the average particle size to 30 μm or less, it is possible to prevent the battery characteristics from being significantly deteriorated due to foreign matters when applied to the electrode. And electrode formation becomes easy and a possibility that it may peel from a collector (copper foil etc.) can be made as small as possible.

If the BET specific surface area is 0.5 m ² / g or more, the surface activity can be increased, and the binding force of the binder during electrode production is reduced, resulting in deterioration of battery characteristics, and charge / discharge. It is possible to reliably prevent a risk that the cycle characteristics are deteriorated when repeated.
Moreover, if it is 30 m < ² > / g or less, the ratio of the silicon dioxide of the particle | grain surface becomes large, and when it uses as a lithium ion secondary battery negative electrode material, it can suppress that a battery capacity falls, and also at the time of electrode preparation It is possible to prevent the solvent absorption amount and the binder consumption amount from increasing.

  Next, although the manufacturing method of the silicon oxide for nonaqueous electrolyte secondary battery negative electrode materials of this invention is demonstrated in detail, of course, it is not limited to these.

First, a raw material that generates SiO gas is prepared.
The raw material for generating this SiO gas is not particularly limited as long as it generates SiO gas. However, silicon monoxide (SiO) or a mixture of silicon dioxide (SiO ₂ ) powder and powder for reducing it is used. Can be used. Specific examples of this reduced powder include metal silicon compounds, carbon-containing powders, and the like, in particular, those using metal silicon powder (1) increase reactivity, (2) increase yield, etc. It is effective in terms and is preferably used.
Thus, if either silicon oxide powder or a mixture of silicon dioxide powder and metal silicon powder is a raw material, it is possible to generate SiO gas with high efficiency because it can be highly reactive and yield can be increased. Can do. Therefore, the silicon oxide of the present invention can be produced with a high yield.

  In addition, when a mixture of metal silicon powder and silicon dioxide powder is used as a raw material, the mixing ratio is appropriately selected. It is desirable that 1 <metal silicon powder / silicon dioxide powder <1.1, particularly 1.01 ≦ metal silicon powder / silicon dioxide powder ≦ 1.08.

The prepared raw material is heated in the presence of an inert gas or under reduced pressure at a temperature of 1,100 to 1,600 ° C., preferably in a temperature range of 1,200 to 1,500 ° C. Is generated.
If the heating temperature is less than 1,100 ° C., the reaction hardly proceeds and the generation amount of SiO gas is reduced, so that the yield is remarkably reduced. On the other hand, when the temperature exceeds 1,600 ° C., the mixed raw material powder is melted, the reactivity is lowered, the amount of generated SiO gas is reduced, and the selection of the reaction furnace material becomes difficult. For this reason, heating temperature shall be in the range of 1,100-1600 degreeC.
In addition, if the inert gas atmosphere or its reduced pressure is not used, the generated SiO gas does not exist stably, resulting in problems that the reaction efficiency of silicon oxide decreases and the yield decreases. The raw material is heated in the presence of gas or under reduced pressure.

Then, a reducing gas is supplied and reacted with the generated SiO gas.
The amount of oxygen in the produced silicon oxide can be easily controlled by the flow rate and time of the reducing gas.
In this reduced gas supply, the atmosphere in the reactor for heating the raw material is an inert gas or under reduced pressure, but thermodynamically, the lower pressure is more reactive and the reaction at low temperature is possible. It becomes. For this reason, specifically, it is desirable to carry out at 1-200 Pa, especially 5-100 Pa.

Further, the reducing gas supplied to the SiO gas is not particularly limited as long as it fulfills the purpose of reducing the SiO gas, but is represented by hydrogen, carbon monoxide, C _n H _4n (n = 1 to 3). It can be a hydrocarbon gas, a gas of ammonia, or a mixed gas thereof. Further, it can be supplied in the form of a mixed gas of these reducing gases and an inert gas such as Ar or He gas.
The gas described above is excellent in reducing power and is suitable for reducing SiO gas. In particular, hydrogen gas does not produce by-products and is advantageous in terms of cost, so that it can be particularly preferably used.

Further, the silicon oxide obtained by the reaction may have an oxygen content of 20 to 35% by mass.
By setting the oxygen content to 20 to 35% by mass, the oxygen content in the obtained reaction product becomes small, and the irreversible reaction between oxygen and lithium in the silicon oxide is suppressed. That is, it is possible to obtain a negative electrode material made of silicon oxide in which the first reduction in charge / discharge efficiency is suppressed more than before, and to obtain a non-aqueous electrolyte secondary battery with higher capacity and excellent cycle characteristics. it can.

Thereafter, the silicon oxide of the present invention is obtained by recovering the reaction product obtained by the reaction.
The method for recovering the reaction product obtained by the reaction between the SiO gas and the reducing gas is not particularly limited. For example, the reaction product is deposited on a deposition substrate in a cooling zone, and sprayed in a cooling atmosphere. Methods and the like. In general, a method in which the above-described mixed gas is allowed to flow in a cooling zone and deposited on a deposition substrate is preferable.

In this case, the type (material) of the precipitation base to be deposited is not particularly limited, but refractory metals such as SUS, molybdenum, and tungsten are preferably used in terms of workability. Further, the precipitation temperature in the cooling zone is preferably 500 to 1000 ° C, particularly 700 to 950 ° C.
If the deposition temperature is 500 ° C. or higher, it is easy to suppress the BET specific surface area of the reaction product from increasing to 30 m ² / g or higher. Moreover, if it is 1000 degrees C or less, selection of the material of a precipitation base | substrate will be easy and will not raise an apparatus cost.
Here, the temperature of the deposition substrate can be appropriately controlled by heating with a heater, heat insulating performance (heat insulating material thickness), forced cooling, or the like.

  Moreover, the silicon oxide for a nonaqueous electrolyte secondary battery negative electrode material deposited on the deposition substrate can be appropriately pulverized by a known means as necessary to obtain a desired particle size.

Moreover, in order to provide electroconductivity, carbon vapor deposition can be performed by a chemical vapor deposition process or mechanical alloying with respect to the obtained silicon oxide for nonaqueous electrolyte secondary battery negative electrode materials.
When carbon coating is performed, the carbon coating amount is preferably 1 to 50% by mass, particularly 1 to 20% by mass, based on the total weight of the silicon oxide coated with carbon.

  This carbon vapor deposition is a reactor for vapor deposition of hydrocarbon compound gas and / or vapor in a temperature range of 600 to 1,200 ° C., more preferably in a temperature range of 800 to 1,100 ° C. under normal pressure or reduced pressure. It can introduce | transduce in and can perform by performing a known thermal chemical vapor deposition process etc. Alternatively, silicon composite particles in which a silicon carbide layer is formed at the silicon-carbon layer interface may be used.

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, Examples thereof include monocyclic to tricyclic aromatic hydrocarbons such as ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, and mixtures 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.

And a lithium ion secondary battery can be manufactured using the negative electrode material for nonaqueous electrolyte secondary batteries which consists of a silicon oxide obtained by this invention.
In this case, the obtained lithium ion secondary battery is characterized in that it uses a negative electrode material in which the silicon oxide of the present invention is used. 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 , chalcogen compounds, and the like are used.
As the electrolyte, for example, a non-aqueous solution containing a lithium salt such as lithium perchlorate is used. As the non-aqueous solvent, propylene carbonate, ethylene carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran or the like or 2 More than one type is used in combination. Various other non-aqueous electrolytes and solid electrolytes can also be used.

In addition, when producing a negative electrode using the negative electrode material for secondary batteries which consists of the said silicon oxide, electrically conductive agents, such as graphite, can be added to a negative electrode material.
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 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.

  In addition, when obtaining an electrochemical capacitor, the electrochemical capacitor is characterized in that the silicon oxide active material of the present invention is used for an electrode, and other materials such as an electrolyte and a separator and a capacitor shape are not limited. .

  For example, as the electrolyte, a non-aqueous solution containing a lithium salt such as lithium hexafluorophosphate, lithium perchlorate, lithium borofluoride, lithium hexafluoroarsenate, etc. is used, and propylene carbonate, ethylene carbonate, A single substance such as dimethyl carbonate, diethyl carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran or a combination of two or more kinds may be used. 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
Silicon oxide was produced using a horizontal tubular furnace as shown in FIG.
Specifically, 50 g of an equimolar mixture of metal silicon powder having an average particle diameter of 5 μm and fumed silica powder (BET specific surface area: 200 m ² / g) as raw material 2 was prepared, and reaction tube 6 made of alumina with an inner diameter of 80 mm. It was charged in.

Next, while the inside of the reaction tube 6 was evacuated by the vacuum pump 7 and depressurized to 20 Pa or less, the temperature was raised to 1400 ° C. by the heater 1 at a temperature rising rate of 300 ° C./hour.
Then, after reaching 1400 ° C., H ₂ gas was allowed to flow into the reaction tube 6 at a flow rate of 1 NL / min via the flow meter 4 and the gas introduction tube 5 (the furnace pressure increased to 70 Pa). After this operation state was continued for 3 hours, the inflow of H ₂ gas and the heater heating were stopped and cooled to room temperature.

After cooling, when the deposit deposited on the deposition substrate 3 was collected, the deposit was a black lump and the collected amount was 38 g.
Next, 30 g of this precipitate was dry pulverized in a 2 L alumina ball mill to produce silicon oxide.
And the average particle diameter and BET specific surface area of the obtained silicon oxide were evaluated. The results are shown in Table 1.

[Battery evaluation]
Next, after the obtained powder (silicon oxide) was treated by the following method, the battery was evaluated as a negative electrode active material.
First, 45 wt% of artificial graphite (average particle diameter 10 μm) and 10 wt% of polyimide were added to the treated powder obtained above, and N-methylpyrrolidone was further added to form a slurry.
The slurry was coated on a copper foil having a thickness of 12 [mu] m, after 1 hour drying at 80 ° C., the electrode was pressure-molded by a roller press, after the electrode was 1 hour vacuum drying at 350 ° C., punched into 2 cm ^2, a negative electrode It was.

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

The prepared lithium ion secondary battery for evaluation was allowed to stand at room temperature overnight, and then charged with a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.) until the voltage of the test cell reached 0 V / 0.5 mA / After charging with a constant current of cm ² and reaching 0V, charging was performed by decreasing the current so that the cell voltage was kept 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.
Moreover, the above charge / discharge test was repeated, the charge / discharge test of 50 cycles of the evaluation lithium ion secondary battery was performed, and the discharge capacity after 50 cycles was evaluated. The evaluation results of the battery evaluation are also shown in Table 1.

(Example 2)
A silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material was produced in the same manner as in Example 1 except that the flow rate of H ₂ gas was 1.5 NL / min. Physical properties and batteries were produced in the same manner as in Example 1. The characteristics were evaluated. The evaluation results are shown in Table 1.

(Example 3)
A silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material was produced in the same manner as in Example 1 except that the flow rate of H ₂ gas was set to 0.3 NL / min. Physical properties and batteries were produced in the same manner as in Example 1. The characteristics were evaluated. The evaluation results are shown in Table 1.

Example 4
A silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material was produced in the same manner as in Example 1 except that CO gas was flowed at 1.0 NL / min as the reducing gas. Battery characteristics were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 1)
A silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material was produced in the same manner as in Example 1 except that no reducing gas was supplied, and physical properties and battery characteristics were evaluated in the same manner as in Example 1. It was. The evaluation results are shown in Table 1.

(Comparative Example 2)
A silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material was produced in the same manner as in Example 1 except that the flow rate of H ₂ gas was set to 2.0 NL / min. Physical properties and batteries were produced in the same manner as in Example 1. The characteristics were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 3)
A negative electrode material using a silicon oxide in which SiO powder having an average particle diameter of 5 μm and Si powder was mixed at a ratio of SiO / Si = 2/1 was produced, and physical properties and battery characteristics were evaluated in the same manner as in Example 1. Went. The evaluation results are shown in Table 1.

As shown in Table 1, the non-aqueous electrolyte secondary battery negative electrode material silicon oxide obtained by the production method of Example 1 has an average particle diameter of 5.3 μm, a BET specific surface area of 8.3 m ² / g, The powder had an oxygen content of 28.6% by mass. The silicon oxide of Example 2 was a powder having an average particle size of 5.2 μm, a BET specific surface area of 9.7 m ² / g, and an oxygen content of 22.1% by mass. The silicon oxide of Example 3 was a powder having an average particle size of 5.3 μm, a BET specific surface area of 6.5 m ² / g, and an oxygen content of 33.8% by mass. Furthermore, the silicon oxide of Example 4 was a powder having an average particle size of 5.3 μm, a BET specific surface area of 8.7 m ² / g, and an oxygen content of 26.7%.
In contrast, the silicon oxide of Comparative Example 1 was a powder having an average particle size of 5.3 μm, a BET specific surface area of 6.3 m ² / g, and an oxygen content of 35.8 mass%. The silicon oxide of Comparative Example 2 was a powder having an average particle size of 5.3 μm, a BET specific surface area of 10.6 m ² / g, and an oxygen content of 18.5% by mass. The silicon oxide of Comparative Example 3 was a powder having an average particle size of 5.1 μm, a BET specific surface area of 5.3 m ² / g, and an oxygen content of 24.8% by mass.

As shown in Table 1, the lithium ion secondary battery using the negative electrode material using the silicon oxide of Example 1 as the negative electrode has an initial charge capacity of 1430 mAh / g, an initial discharge capacity of 1180 mAh / g, and an initial charge. A lithium ion secondary battery with a discharge capacity of 82.5%, a discharge capacity of 1150 mAh / g at the 50th cycle and a cycle retention of 97% after the 50th cycle, a high capacity and excellent initial charge / discharge efficiency and cycle performance. It was confirmed that there was.
Further, the lithium ion secondary battery using the silicon oxide of Example 2 has an initial charge capacity of 1510 mAh / g, an initial discharge capacity of 1280 mAh / g, an initial charge / discharge efficiency of 84.8%, and a discharge capacity of 1210 mAh at the 50th cycle. / G, the cycle retention after 50 cycles was 95%, which was high capacity as in Example 1, and excellent in initial charge / discharge efficiency and cycleability.
A lithium ion secondary battery using the silicon oxide of Example 3 has an initial charge capacity of 1350 mAh / g, an initial discharge capacity of 1080 mAh / g, an initial charge / discharge efficiency of 80.0%, and a 50th cycle discharge capacity of 1060 mAh. / G, the cycle retention after 50 cycles was 98%, and as in Examples 1 and 2, the capacity was high and the initial charge / discharge efficiency and cycleability were excellent.
The lithium ion secondary battery using the silicon oxide of Example 4 has an initial charge capacity of 1440 mAh / g, an initial discharge capacity of 1200 mAh / g, an initial charge and discharge efficiency of 83.3%, and a discharge capacity of 1150 mAh / g at the 50th cycle. As in Example 1-3, the cycle retention after 50 cycles was 96%, and the capacity was high, and the initial charge / discharge efficiency and cycleability were excellent.

In contrast, a lithium ion secondary battery using the silicon oxide of Comparative Example 1 has an initial charge capacity of 1310 mAh / g, an initial discharge capacity of 1000 mAh / g, an initial charge / discharge efficiency of 76.3%, and a 50th cycle discharge. Since the capacity is 980 mAh / g, the cycle retention after 50 cycles is 98%, and the cycle performance is better than when the silicon oxide of Example 1-4 is used, the oxygen content is large. It was confirmed that the lithium ion secondary battery was clearly inferior in initial charge / discharge efficiency.
Moreover, the lithium ion secondary battery using the silicon oxide of Comparative Example 2 has an initial charge capacity of 1560 mAh / g, an initial discharge capacity of 1370 mAh / g, an initial charge / discharge efficiency of 87.8%, and a discharge capacity of 1180 mAh at the 50th cycle. / G, the cycle retention after 50 cycles is 86%, and the oxygen content is too small compared to the case of using the silicon oxide of Example 1-4. It was confirmed to be a secondary battery.
The lithium ion secondary battery using the silicon oxide of Comparative Example 3 has an initial charge capacity of 1500 mAh / g, an initial discharge capacity of 1290 mAh / g, an initial charge / discharge efficiency of 86.0%, and a 50th cycle discharge capacity of 760 mAh. / G, the cycle retention after 50 cycles is 59% and the oxygen content is similar to that of Example 1-4, but compared with the case of using the silicon oxide of Example 1-4. As a result, it was confirmed that the lithium ion secondary battery was clearly inferior in cycle performance. This is because the silicon oxide of Comparative Example 3 is not manufactured by reacting SiO gas and reducing gas as in Example 1-4, but is a mixture of SiO powder and Si powder. is there. This is considered to be because in Comparative Example 3, there are locations where the composition is not locally stable.

  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 ... Heater, 2 ... Raw material, 3 ... Precipitation base, 4 ... Flowmeter, 5 ... Gas introduction pipe, 6 ... Reaction pipe, 7 ... Vacuum pump.

Claims (8)

A silicon oxide used for a negative electrode material for a secondary battery using a non-aqueous electrolyte,
The silicon oxide has an oxygen content of 20 to 35% by mass, and is obtained by reacting SiO gas with a reducing gas. For non-aqueous electrolyte secondary battery negative electrode material Silicon oxide. The non-aqueous electrolyte secondary battery negative electrode according to claim 1, wherein the silicon oxide is a particle having an average particle diameter of 0.1 to 30 μm and a BET specific surface area of 0.5 to 30 m ² / g. Silicon oxide for materials. A lithium ion secondary battery comprising at least a positive electrode, a negative electrode, and a lithium ion conductive non-aqueous electrolyte,
A lithium ion secondary battery, wherein the negative electrode material is a silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material according to claim 1 or 2. An electrochemical capacitor comprising at least a positive electrode, a negative electrode, and a conductive electrolyte,
An electrochemical capacitor, wherein the negative electrode material is the non-aqueous electrolyte secondary battery negative electrode material silicon oxide according to claim 1 or 2 used as a negative electrode material. A method for producing a silicon oxide used in a negative electrode material for a secondary battery using a non-aqueous electrolyte,
At least a raw material that generates SiO gas is heated in the temperature range of 1,100 to 1,600 ° C. in the presence of an inert gas or under reduced pressure to generate SiO gas,
A reducing gas is supplied to the generated SiO gas for reaction,
A method for producing a silicon oxide for a negative electrode of a non-aqueous electrolyte secondary battery, wherein a reaction product obtained by the reaction is recovered.   The method for producing a silicon oxide for a negative electrode material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the reactant is a silicon oxide having an oxygen content of 20 to 35 mass%.   The silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material according to claim 5 or 6, wherein the raw material is either silicon oxide powder or a mixture of silicon dioxide powder and metal silicon powder. Manufacturing method. The reducing gas includes any one of hydrogen, carbon monoxide, hydrocarbon gas represented by C _n H _4n (n = 1 to 3), ammonia, or a mixed gas thereof. The method for producing a silicon oxide for a non-aqueous electrolyte secondary battery negative electrode material according to any one of claims 5 to 7, wherein:

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