JP2003192327A - Method of and device for producing metallic element- doped silicon oxide powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic element-doped silicon oxide powder in which a lithium ion secondary battery having a high capacity and excellent in both initial charge/discharge efficiency and cycle characteristic can be obtained by the use thereof as a negative electrode active material for the above secondary battery. <P>SOLUTION: This metallic element-doped silicon oxide powder is produced by heating a raw material powder mixture containing silicon dioxide powder in the presence of an inert gas or under a reduced pressure within a temperature range of 1,100-1,600°C, generating gaseous silicon oxide, heating the metals or metal compounds except silicon, or the mixture thereof to generate their vaporized gases, and depositing the mixture of the gaseous silicon oxide and vaporized metallic gases on the surface of a substrate cooled to 100-500°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a metal element-doped silicon oxide powder having various functionalities and an apparatus for producing the same, and particularly to a metal element-doped silicon oxide suitable for a negative electrode material for a lithium ion secondary battery. The present invention relates to a powder manufacturing method and a manufacturing apparatus thereof.

[0002]

2. Description of the Related Art In recent years, with the remarkable development of portable electronic devices, communication devices, etc., a high energy density secondary battery has been 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 of using an oxide such as V, Si, B, Zr, Sn or a composite oxide thereof as a negative electrode material (Japanese Patent Laid-Open No. 5-17)
No. 4818, Japanese Unexamined Patent Publication No. 6-60867, etc.), a method of applying a melt-quenched metal oxide as a negative electrode material (Japanese Unexamined Patent Publication No. 10-294112), a method of using silicon oxide as a negative electrode material (Japanese Patent No. 2997741) Gazette), a method of using Si ₂ N ₂ O and Ge ₂ N ₂ O as a negative electrode material (JP-A-1
No. 1-102705) and the like are known.

[0003]

However, in the above conventional method, although the charge / discharge capacity and the energy density are increased, the cycle property is insufficient and the required characteristics of the market are still insufficient. However, it is not always satisfactory, and further improvement in energy density has been desired.

Among them, the method of using silicon oxide as the negative electrode material (Japanese Patent No. 2997741) gives a lithium ion secondary battery having a very high capacity, but the cycle performance is insufficient.

The present invention has been made in view of the above circumstances, and is a metal element-doped oxidation suitable as a negative electrode material for a lithium ion secondary battery, which has a high capacity, does not cause cycle deterioration, and has a small irreversible capacity during initial charge / discharge. An object of the present invention is to provide a silicon powder manufacturing method and a manufacturing apparatus thereof.

[0006]

Means for Solving the Problems and Modes for Carrying Out the Invention The inventors of the present invention have made extensive studies to achieve the above-mentioned object, and have made various studies on silicon oxide, which is considered to have a particularly high capacity. As a result, silicon oxide was atomically dispersed and doped with another metal element, and by using this metal element-doped silicon oxide powder as a negative electrode material, there was no cycle deterioration while maintaining a high capacity, and the initial charging was performed. The present invention has been completed by finding that a lithium ion secondary battery having a small irreversible capacity during discharge can be manufactured.

Therefore, according to the present invention, (1) a mixed raw material powder containing a silicon dioxide powder is heated in the temperature range of 1100 to 1600 ° C. in the presence of an inert gas or under reduced pressure to generate a silicon oxide gas, while other than silicon. The metal or metal compound or mixture thereof is heated to generate a metal vapor gas, and a mixed gas of the silicon oxide gas and the metal vapor gas is deposited on a substrate surface cooled to 100 to 500 ° C. And (2) a reaction chamber A in which a mixed raw material containing silicon dioxide powder is reacted to generate a silicon oxide gas, and a metal or metal compound other than silicon or a mixture thereof. A reaction chamber B that is heated to generate a metal vapor gas, and a gas transfer line that connects the reaction chamber A and the reaction chamber B and mixes and transfers the two types of gas described above; Providing an apparatus for manufacturing a metal element doped silicon oxide having a a feed has been mixed gas deposition chamber to deposit the cooled substrate surface.

The present invention will be described in more detail below.

In the method for producing a metal element-doped silicon oxide powder of the present invention, a mixture of silicon dioxide powder and a powder for reducing the same is used as a raw material for generating silicon oxide gas. Specific reduction powders include metallic silicon compounds,
Carbon-containing powders and the like can be mentioned. Particularly, powders using metallic silicon powder are effective in terms of enhancing reactivity and yield and are preferably used.

In this case, the ratio of silicon dioxide to the powder for reducing it is appropriately selected, but SiO _x (x = 0.9)
.About.1.6, especially 1.0 to 1.2).

In the present invention, the above mixed raw material powder is added to the reaction chamber A.
Within 1100 to 1600 ° C, preferably 1200
It is heated and maintained at a temperature of up to 1500 ° C. to generate silicon oxide gas. If the reaction temperature is lower than 1100 ° C, the reaction is difficult to proceed and the productivity is lowered. If the reaction temperature is higher than 1600 ° C, the mixed raw material powder is melted to lower the reactivity.
It may be difficult to select the furnace material.

On the other hand, as the metal element to be doped into silicon oxide, a metal or metal compound other than the above-mentioned mixed powder (other than silicon) or a mixture thereof is heated and held in the reaction chamber B,
Generates metal gas. In this case, the heating temperature is determined by the vapor pressure of the metal to be doped into silicon oxide and the preset metal doping amount. For example, when it is desired to dope silicon oxide in the same amount, the heating temperature is almost the same as that of silicon oxide gas. The temperature should be set to Here, in the case of doping a metal element in which the vapor pressure of the metal element is close to the vapor pressure of silicon oxide, the silicon oxide gas generating raw material and the metal element generating raw material may be mixed and performed simultaneously in one reaction chamber. it can.

In this case, the atmosphere in the furnace is an inert gas or under reduced pressure, but thermodynamically under reduced pressure has higher reactivity and a low temperature reaction is possible, so it is desirable to carry out under reduced pressure. .

Further, considering that the above-mentioned metal to be doped into silicon oxide can impart conductivity, and can control a crystal structure (spinel structure) suitable for doping and dedoping of lithium ions. , Al, B, C
One or more of a, K, Na, Li, Ge, Mg, Co and Sn are preferably used.

The amount of the metal to be doped into the silicon oxide is not particularly limited and may be appropriately selected depending on the purpose and application. Generally, the total amount (weight) of the silicon oxide powder after the doping is the same. 3 to 70% by weight, preferably 5 to
It can be about 50% by weight. If the doping amount of this metal is less than 3%, the effect may not be effectively exhibited, and if it is more than 70% by weight, Si
The content of O is reduced and the charge / discharge capacity is reduced, and as a result, the capacity of SiO may not be fully exhibited.

The two kinds of gases produced in the reaction chambers A and B are mixed in the gas transfer line, and this mixed gas is supplied to the deposition chamber through the gas transfer line.

In this case, the conveying line has a temperature of more than 1000 ° C. and 1300 ° C. or less, more preferably 1100 to 1200.
It is desirable to heat and hold at ℃. Here, the purpose of heating the carrier pipe is to prevent deposition of silicon oxide vapor on the inner wall of the carrier pipe, and when the temperature of the carrier pipe is 1000 ° C. or less, a mixed gas containing silicon oxide gas is deposited and adheres to the inner wall of the carrier pipe. However, there is a risk that operation will be hindered and stable continuous operation may not be possible. On the contrary, even if it is heated to a temperature of more than 1300 ° C., no further effect is seen, and the power cost is increased.

A substrate cooled by a cooling medium is placed in the deposition chamber, and the mixed gas introduced into the deposition chamber is brought into contact with and cooled by the cooling substrate to contain silicon oxide on the substrate. The product precipitates. Here, it is necessary to control the temperature of the substrate surface to 100 to 500 ° C.
When the surface temperature of the substrate is lower than 100 ° C., the BET specific surface area of the product becomes larger than 300 m ² / g, and the ratio of inactive silicon dioxide due to surface oxidation becomes large. When used as a negative electrode material for a lithium ion secondary battery. , I can't get a high capacity battery. On the contrary, when the temperature of the substrate surface is higher than 500 ° C., the BET specific surface area becomes less than 3 m ² / g, the activity is lowered, and a high capacity battery cannot be obtained. The cause of the change in the BET specific surface area depending on the surface temperature of the substrate is not clear, but the activity of the precipitate surface is increased by increasing the temperature of the substrate surface.
It is presumed that the T specific surface area decreases. The temperature of the substrate surface is controlled by the combination of the temperature in the deposition chamber (heated by the deposition chamber heater), the type of refrigerant, and the flow rate. The type of refrigerant is not particularly limited,
Liquids such as water and heat medium, and gases such as air and nitrogen are used depending on the purpose. The type of the base is not particularly limited, but a refractory metal such as SUS, molybdenum, or tungsten is preferably used in terms of workability.

The metal element-doped silicon oxide deposited on the substrate is collected by an appropriate means such as scraping. Further, the recovered silicon oxide powder can be crushed by an appropriate means to obtain a desired particle size, if necessary.

As the apparatus used in the above method, for example, the apparatus shown in FIG. 1 can be used. Here, in FIG. 1, reference numeral 1 is a reaction furnace A, and a muffle A2 is arranged in the reaction furnace A1. A reaction chamber A3 is formed in the muffle A2, and a raw material container A5 for containing the mixed raw material powder 4 containing silicon dioxide powder is arranged in the reaction chamber A3. Further, a heater 6 is arranged so as to surround the muffle A2, and the mixed raw material 4 is heated by the heater 6 to generate a silicon oxide gas. In addition, 7 is a heat insulating material.

On the other hand, 8 is a reaction furnace B, and similarly to the above, a muffle B9 is arranged in this reaction furnace B8, and the inside of this muffle B9 is a reaction chamber B10, and inside this reaction chamber B10. A raw material container B12 for containing a powder 11 of another metal or a metal compound or a mixture thereof is arranged. Further, a heater 13 is arranged so as to surround the muffle B9, and the powder 13 is provided by the heater 13.
Is heated to generate metal element gas. In addition, 14 is a heat insulating material.

Further, 15 is both reaction chambers A3 and B1.
The heater 16 is embedded in a transfer line which communicates with 0 and in which the silicon oxide gas and the metal element gas generated in the reaction chambers A3 and B10 flow in and are mixed. The transfer line 15 communicates with the deposition chamber 17 of the deposition tank 18 in which the deposition chamber 17 is further formed, and each of the reaction chambers A
2 and the two kinds of gas generated in B10 are mixed in the transfer line 15 and passed through the transfer line 15 and the deposition tank 18
It is introduced into the deposition chamber 17 inside. A heater 19 and a substrate 20 are provided in the deposition chamber 17. A cooling passage is formed in the base body 20, and the base body 20 is cooled by the coolant supplied from the coolant introducing pipe 21 to the coolant passage, and the mixed gas containing the silicon oxide comes into contact with the cooling base body 20 and is cooled. By being
A metal element-doped silicon oxide powder is deposited on the substrate 20. Reference numeral 22 is a refrigerant discharge pipe. Further, a thermocouple 23 is embedded in the cooling base 20, and the surface temperature of the cooling base 20 can be measured. Reference numeral 24 denotes a vacuum pump. By operating this vacuum pump 24, the deposition chamber 17, the transfer line 15, and the reaction chambers A3 and B10 are depressurized.

Next, the metal element-doped silicon oxide obtained in the present invention can be used as a negative electrode material to manufacture a lithium ion secondary battery.

In this case, the obtained lithium ion secondary battery is characterized by using the above-mentioned negative electrode active material, and other materials such as the positive electrode, the negative electrode, the electrolyte and the separator and the battery shape are not limited. For example, as the positive electrode active material, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , V ₂ O ₆ , M
Oxides of transition metals such as nO ₂ , TiS ₂ and MoS ₂ and chalcogen compounds are used. As the electrolyte, for example, a non-aqueous solution containing a lithium salt such as lithium perchlorate is used, and as the non-aqueous solvent, propylene carbonate, ethylene carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran or the like alone or in two kinds. The above is used in combination. In addition, various other non-aqueous electrolytes and solid electrolytes can also be used.

The metal element-doped silicon oxide of the present invention may be added with a conductive agent such as graphite, and in this case, the kind of the conductive agent is not particularly limited, and decomposition or deterioration of the constructed battery is prevented. Any electron-conducting material that does not cause it may be used. Specifically, Al, Ti, Fe, Ni, C
metal powder or metal fiber such as u, Zn, Ag, Sn, Si,
Or natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor grown carbon fiber, pitch-based carbon fiber, P
Graphite such as AN-based carbon fibers and various resin fired bodies can be used.

[0026]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, wt% means% by weight.

Example 1 Using the manufacturing apparatus shown in FIG. 1,
A Ti-doped silicon oxide powder was produced. The silicon oxide gas generating raw material is silicon dioxide powder (BET specific surface area = about 200 m
² / g) powder and metallic silicon powder (BET specific surface area = about 3 m ²
/ G) was mixed in an equimolar ratio using a stirring mixer, and 200 g was charged in a reaction furnace A1 having an effective volume of 15 L in the reaction chamber A3. On the other hand, Ti is used as a Ti gas generating raw material, and the effective volume of the reaction chamber B10 is 1
200 g was charged in a 5 L reactor B8. Next, using a vacuum pump 24, after decompressing the inside of the furnace to 0.1 Torr or less, the heater 6 and the heater 13 are heated, the reaction furnace A is 1350 ° C. (SiO vapor pressure 3 Torr), and the reaction furnace B is 2100 ° C. ( The Ti vapor pressure was kept at 3 Torr) by heating. On the other hand, the transfer line 15 was set to 1100 ° C.
8 is heated and held at 850 ° C.
L / min was introduced to cool the SUS substrate 20. The surface temperature of the substrate 20 at this time was measured by the thermocouple 23 and was about 180 ° C. After this operation was performed for 5 hours, it was cooled to room temperature and observed. As a result, formation of 210 g of a black material was found on the substrate 20. As a result of analyzing this black material, it was Ti-doped silicon oxide having a BET specific surface area of 35 m ² / g and a Ti content of 43 wt%.

Next, 100 g of this intermediate was pulverized with a ball mill made of 2 L alumina, using 1000 g of φ5 mm alumina balls as a medium and 500 g of hexane as a solution.
Wet grinding was performed under the rotation condition of 1 rpm. T after crushing
The i-doped silicon oxide powder has an average particle size of 7.3 μm, BE
T specific surface area = 40.2 m ² / g, Ti content = 42.5
It was a powder of wt%.

Battery Evaluation Next, battery evaluation was carried out by using the obtained Ti-doped silicon oxide powder as a negative electrode active material by the following method.

First, artificial graphite (average particle diameter 5 μm) was added to the obtained Ti-doped silicon oxide powder at a carbon ratio of 40 wt.
% To make a mixture. Polyvinylidene fluoride was added to this mixture in an amount of 10 wt% and N-methylpyrrolidone was further added to form a slurry. The slurry was applied to a copper foil having a thickness of 20 μm and dried at 120 ° C. for 1 hour.
The electrode is pressure-molded by a roller press, and finally 2
It was punched out to 0 mm and used as 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 phosphorus hexafluoride was used as a non-aqueous electrolyte in 1 / of ethylene carbonate and 1,2-dimethoxyethane. A lithium ion secondary battery for evaluation was prepared using a nonaqueous electrolyte solution dissolved in a 1 (volume ratio) mixed solution at a concentration of 1 mol / L and using a polyethylene microporous film having a thickness of 30 μm as a separator.

The produced lithium ion secondary battery was left overnight at room temperature and then, using a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.), a constant current of 1 mA was applied until the voltage of the test cell reached 0V. After reaching 0 V, the current was reduced so as to keep the cell voltage at 0 V, and then charging was performed. Then, the charging was terminated when the current value fell below 20 μA. The discharge was performed at a constant current of 1 mA, the discharge was terminated when the cell voltage exceeded 1.8 V, and the discharge capacity was obtained.

The above charge / discharge test was repeated to perform a charge / discharge test after 10 cycles of the evaluation lithium ion secondary battery. As a result, initial charge capacity: 920 mAh / g, initial discharge capacity: 850 mAh / g, efficiency during initial charge / discharge:
92.4%, discharge capacity at 10th cycle: 780 mAh
/ G, cycle retention rate after 10 cycles: High capacity of 91.7%, and it was confirmed that the lithium ion secondary battery was excellent in initial charge / discharge efficiency and cycleability.

[Example 2] Li-doped silicon oxide was produced in the same manner as in Example 1. L as a Li gas generating raw material
Using i, 200 g of Li powder was put in a polyethylene bag in the glove box, and charged into the reaction furnace B while maintaining a sealed state. Reactor B is 770 ° C. (Li
The vapor pressure was kept at 3 Torr). Others are the same as in the first embodiment. As a result, a black material 22 is formed on the surface of the substrate 20.
It was possible to produce 0 g of product. As a result of analyzing this black material, it was found that the Li-doped silicon oxide had a BET specific surface area of 28 m ² / g and a Li content of 51 wt%. Next, pulverization was performed in the same manner as in Example 1 to obtain an average particle size of 7.1 μm.
m, BET specific surface area = 37.5 m ² / g of powder was obtained.

Using the obtained Li-doped silicon oxide powder as a negative electrode material, battery evaluation was carried out in the same manner as in Example 1, and as a result,
Initial charge capacity: 780 mAh / g, Initial discharge capacity: 75
0 mAh / g, efficiency at first charge / discharge: 96.2%, 10
It was confirmed that the lithium-ion secondary battery was excellent in cycle performance with the discharge capacity at the cycle cycle: 730 mAh / g and the cycle retention rate after 10 cycles: 97.3%.

Comparative Example A silicon oxide powder not doped with a metal element was produced in the same manner as in Example 1 except that the reaction furnace B was not charged with a metal or a metal compound and the reaction furnace B was not heated. As a result, 120 g of silicon oxide having a purity of 99.5% could be manufactured. Next, pulverization was performed in the same manner as in Example 1 to obtain an average particle size of 8.1 μm and a BET specific surface area = 35.2 m ² /
A high-purity silicon oxide powder containing no g of a metal element was obtained.

Using the obtained silicon oxide powder as a negative electrode material, battery evaluation was performed in the same manner as in Example 1. As a result, initial charge capacity: 900 mAh / g, initial discharge capacity: 650 mAh /
g, efficiency at first charge / discharge: 72.2%, discharge capacity at 10th cycle: 500 mAh / g, cycle retention rate after 10 cycles: 76.9%, which is a high capacity, but clearly compared to the examples. The secondary battery was inferior in cycleability.

[0038]

By using the metal element-doped silicon oxide of the present invention as a negative electrode active material for a lithium ion secondary battery, it is possible to obtain a lithium ion secondary battery having high capacity and excellent initial charge / discharge efficiency and cycle characteristics. it can.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a manufacturing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 Reactor A 2 muffle A 3 Reaction chamber A 4 Mixed raw material powder 5 Raw material container A 6 heater 7 insulation 8 Reactor B 9 Muffle B 10 Reaction chamber B 11 Metal powder 12 Raw material container B 13 heater 14 Insulation 15 Transport line 16 heater 17 Deposition chamber 18 deposition tank 19 heater 20 base 21 Refrigerant introduction pipe 22 Refrigerant discharge pipe 23 thermocouple 24 vacuum pump

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mikio Aramata             2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu             Gakuin Co., Ltd. Gunma Office (72) Inventor Kazuma Umai             2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu             Gakuin Co., Ltd. Gunma Office (72) Inventor Satoru Miyawaki             2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu             Gakuin Co., Ltd. Gunma Office F term (reference) 4G072 AA24 AA38 BB05 GG03 HH14                       LL03 MM01 RR11 UU30                 5H029 AJ02 AJ03 AJ05 AL02 AL11                       AM03 AM04 AM05 AM07 CJ02                       CJ08 CJ15 CJ28 CJ30 DJ16                       HJ14                 5H050 AA02 AA07 AA08 BA16 CB02                       CB11 FA17 GA02 GA10 GA16                       GA27 GA29 HA14

Claims (3)

[Claims] 1. A mixed raw material powder containing silicon dioxide powder is heated to 1100 to 1600 ° C. in the presence of an inert gas or under reduced pressure.
While heating in the temperature range of 1 to generate silicon oxide gas,
A metal other than silicon, a metal compound, or a mixture thereof is heated to generate a metal vapor gas, and a mixed gas of the silicon oxide gas and the metal vapor gas is deposited on a substrate surface cooled to 100 to 500 ° C. A method for producing a silicon oxide powder doped with a metal element. 2. The metal is Al, B, Ca, K, Na,
The method for producing a metal element-doped silicon oxide powder according to claim 1, which is one or more selected from Li, Ge, Mg, Co and Sn. 3. A reaction chamber A for reacting a mixed raw material containing silicon dioxide powder to generate a silicon oxide gas, and a reaction chamber for heating a metal or metal compound other than silicon or a mixture thereof to generate a metal vapor gas. B, a metal transport line for connecting the reaction chamber A and the reaction chamber B, a gas transport line for mixing and transporting the above-mentioned two kinds of gas, and a deposition chamber for depositing the transported mixed gas on the cooled substrate surface Silicon oxide manufacturing equipment.