JP4624830B2 - Carbonaceous materials for electrode materials - Google Patents

Description

  The present invention relates to a carbonaceous material and a low-temperature calcined carbon powder suitable for use as raw materials for producing high-performance electrode materials such as activated carbon for electric double layer capacitors and negative electrode active materials for lithium secondary batteries, and electrodes for power storage devices. Regarding materials.

In recent years, new power storage devices such as electric double layer capacitors and lithium ion secondary batteries have been developed one after another. The power storage device has a higher capacity and / or higher output than conventional storage batteries and capacitors, and is widely used from portable electronic devices such as mobile phones and laptop computers to relatively large devices such as hybrid electric vehicles. Yes.

  The power storage device uses carbon materials such as activated carbon, graphite, and low-temperature calcined carbon as its electrode material, and the carbon material has physical properties such as conductivity, intercalation compound forming ability, chemical resistance, and the like. In terms of supply stability and cost efficiency, it is superior to electrode materials mainly composed of other elements. However, at the same time, since the characteristics of the carbon material greatly affect the performance of the power storage device, special attention must be paid to the method of manufacturing the carbon material.

  In the electric double layer capacitor, the capacitance depends on the specific surface area, pore distribution, crystallinity, purity and the like of the activated carbon particles constituting the electrode of the electric double layer capacitor. Therefore, in order to obtain an activated carbon suitable for an electric double layer capacitor, it is necessary to subject the carbonaceous material as a raw material to various treatments such as pulverization, carbonization, and activation.

The process for producing activated carbon using the above carbonaceous material as a raw material is generally as follows, although it varies slightly depending on the type of carbonaceous material used.
That is, the dried carbonaceous material is first pulverized into particles having a particle size of several mm or less. Next, the pulverized carbonaceous material is carbonized at a temperature range of 600 to 900 ° C. in an inert atmosphere. Next, the carbide is activated in a state where steam is introduced or potassium hydroxide is added and mixed. Further, the activation product is pickled or washed with dilute hydrochloric acid. Finally, impurities are removed by sieving to make activated carbon.

In the lithium secondary battery, the capacity depends on the physical properties of the active material constituting the positive electrode and the negative electrode. That is, as the negative electrode active material, mainly graphite-based and / or low-temperature calcined carbon-based carbon is used, and both of them have specific surface area, pore distribution, crystallinity, purity, etc. of the negative electrode active material particles. Greatly affects. Therefore, in order to obtain a negative electrode active material suitable for a lithium secondary battery, it is necessary to subject the carbonaceous material as a raw material to various treatments such as pulverization, carbonization, and graphitization.

The manufacturing process of the low-temperature-fired carbon-based negative electrode active material using the above-mentioned carbonaceous material as a raw material is generally as follows, although it varies slightly depending on the type of carbonaceous material used.
That is, the dried carbonaceous material is first pulverized into particles having a particle size of several mm or less. Next, the pulverized carbonaceous material is carbonized at a temperature range of 800 to 1,400 ° C. in an inert atmosphere. Further, the obtained carbide is pulverized to a predetermined average particle size. In this way, a low-temperature fired carbon-based negative electrode active material is obtained.

The graphite-based negative electrode active material is usually obtained by subjecting the carbide to the following treatment.
That is, if necessary, a graphitization catalyst such as boron oxide is added to and mixed with the carbide pulverized to the predetermined average particle diameter obtained above. An appropriate amount of caking material such as coal tar pitch is added to the mixture and mixed. The mixture is then graphitized at 2,800-3,000 ° C. under an argon atmosphere. Furthermore, the obtained graphitized material is crushed and adjusted to a predetermined average particle size. In this way, a graphite-based negative electrode active material is obtained.

As described above, in any production process of activated carbon for electric double layer capacitors and negative electrode active material for lithium secondary battery, production of low-temperature calcined carbon powder (hereinafter referred to as carbonized product) having a predetermined average particle size There is a process. That is, the carbonaceous material usually contains a functional group composed of a volatile component or other elements in addition to the carbon hexagonal network surface and / or carbon crystal necessary for the electrode material. However, the volatile components and functional groups composed of other elements may cause problems in the activation process for producing activated carbon or the graphitization process for obtaining graphite crystals. Therefore, in the manufacturing process of the carbonized product, it becomes possible to manufacture the electrode material without any trouble by removing the functional group composed of the volatile component and other elements or converting it into a carbon hexagonal network surface and / or a carbon crystal. . In addition, before and after the carbonized product manufacturing process, the carbonaceous material is pulverized to a predetermined average particle size for the electrode material, whereby the yield in the subsequent process can be increased. For these reasons, the manufacturing process of the carbonized product is required in the manufacturing process of the electrode material for the power storage device.

  However, in a conventional carbonized product manufacturing process, for example, in a process of pulverizing a dried carbonaceous material into particles having a particle size of several millimeters or less, iron from a pulverizer is mixed into the carbonized product, or carbon before and after carbonization. Manufacturing problems such as the generation of a large amount of fine powder in the process of pulverizing the material to a predetermined average particle size for the electrode material may occur.

If iron is mixed in the carbonized product, problems such as short circuit between electrodes and decomposition of the electrolytic solution occur, which is not preferable. Depending on the iron content, the carbonized product becomes a defective product.
In addition, fine powder in the electrode material, particularly fine powder having a particle diameter of less than 1 μm, is bulky and obstructs the production of a uniform electrode sheet, and must be removed from the carbonized product. As a result, the yield of the electrode material is reduced, and therefore generation of fine powder is undesirable.

  An effective solution has not yet been known with respect to the mixing of iron into the carbonized product and the generation of fine powder, which are the problems of the prior art.

  The present invention has been made in view of the above-described problems of the prior art, and can improve the purity and yield of the electrode material. The carbonaceous material for electrode material, the low-temperature-fired carbon powder (carbonized product), and the electricity storage using the same. It is an object to provide an electrode material for a device.

  The present inventors have performed a pulverization (hereinafter referred to as fine pulverization) step for obtaining a predetermined average particle diameter, and a pulverization (hereinafter referred to as coarse particle) for reducing the particle size of the carbonaceous material to be several mm or less before the fine pulverization step. Various processes (called pulverization) were studied. As a result, surprisingly, in the carbonaceous material after coarse pulverization, the iron content in the powder having a particle size of 0.05 mm or less is higher than that in the powder exceeding 0.05 mm, and the carbonaceous material after coarse pulverization It has been found that when fine pulverization is performed after removing powder having a diameter of 0.05 mm or less, generation of fine powder having a particle diameter of 1 μm or less is suppressed. In addition, it has been found that the iron content in the carbonaceous material after coarse pulverization is reduced by changing the material of the hammer of the pulverizer from carbon steel to austenitic steel.

Further, after coarse pulverization, the particle size distribution of the carbonaceous material is preferably classified by a sieve so that particles having a particle size of 2 mm or more are 0.1% by weight or less, and particles having a particle size of 0.05 mm or less are 0.1% by weight or less. Found that the material of the hammer of the pulverizer is austenitic steel, so that the iron content in the carbonized product can be greatly reduced and fine powder generated in the pulverization process can be suppressed.

That is, according to the first invention of the present invention, in a carbonaceous material made of coke obtained by heat treating petroleum-based and / or coal-based heavy oil, particles having a particle diameter of 2 mm or more in the coke are 0.1% by weight. A carbonaceous material for electrode material is provided that is roughly pulverized and classified so that particles having a particle size of 0.05 mm or less are 0.1 wt% or less.

  According to the second invention of the present invention, in the coarse pulverization of the carbonaceous material made of coke in the first invention, the carbonaceous material for electrode material using a pulverizer in which the pulverized portion of coke is made of austenitic steel is provided. Provided.

According to the third invention of the present invention, the carbonaceous material after the coarse pulverization and classification in the first invention is further pulverized to an average particle size of 1 μm to 30 μm and then at a temperature of 600 ° C. to 1,400 ° C. There is provided a low-temperature fired carbon powder (carbonized product) for electrode materials which is fired or pulverized to a mean particle size of 1 μm to 30 μm after firing at a temperature of 600 ° C. to 1,400 ° C.

Furthermore, according to the 4th invention of this invention, the electrode material for electrical storage apparatuses which consists of the low-temperature baking carbon powder (carbonized product) in 3rd invention is provided.
According to the fifth aspect of the present invention, there is provided an electrode material for a power storage device comprising a carbon powder obtained by further activating or graphitizing the low-temperature calcined carbon powder (carbonized product) in the third aspect.

  By using the coarsely pulverized carbonaceous material of the present invention, the iron content in the carbonized material used as the raw material of the electrode material for the power storage device is maintained at substantially the same value as the carbonaceous material before coarsely pulverized, and the production of the carbonized product is performed. It is possible to suppress the amount of fine powder generated in the fine pulverization process.

The carbonaceous material of the present invention is coke obtained by heat-treating petroleum heavy oil and / or coal heavy oil. Coke is usually obtained by heat treating petroleum heavy oil and / or coal heavy oil at 400 to 600 ° C. Industrially, a delayed coker is used for the heat treatment, and an amount of about several thousand tons per batch is produced. The coke taken out from the delayed coker has an indefinite size, so it is crushed with a roll crusher or the like to make a mass of several tens of centimeters. Also, the coke mass is dried if necessary.

The carbonaceous material (coke crushed material) obtained as described above is coarsely pulverized so that particles having a particle diameter of 2 mm or more are 0.1% by weight or less in order to improve the subsequent process passability. The pulverizer used for the coarse pulverization is preferably an impact or shear type pulverizer capable of obtaining a medium particle size, and examples thereof include a hammer mill, an attrition mill, a cutter mill, and a pin mill. The material for the pulverized portion when coarsely pulverizing the carbonaceous material is preferably austenitic steel. Examples of the austenitic steel include SUS304 and SUS310S. Carbon steel or cast iron as the material of the pulverized part when coarsely pulverizing carbonaceous material is easily rusted and easily worn or damaged during coarse pulverization of the coke mass, so that carbon steel or cast iron is mixed in the carbonaceous material. Therefore, it is not preferable.

Coarse pulverization conditions are adjusted so that the proportion of particles having a particle diameter of 2 mm or more contained in the coarsely pulverized carbonaceous material is 0.1% by weight or less. For example, it can be carried out by appropriately adjusting conditions such as the amount charged into the pulverizer and the pulverization time according to the carbonaceous material to be coarsely pulverized. If necessary, a preliminary test may be performed in advance to adjust the coarse pulverization conditions.

When the ratio of particles of 2 mm or more exceeds 0.1% by weight, clogging occurs in the connecting pipe from the feeder of the fine pulverizer to the nozzle of the fine pulverizer, which is not preferable in the fine pulverization process.
As the particle size distribution of the coarsely pulverized carbonaceous material, when the coarsely pulverized carbonaceous material is classified with a sieve of 60 mesh (aperture 250 μm), the coarse pulverization conditions are adjusted so that the sieve top is 50% by weight or more. It is particularly preferable. Under grinding conditions such that the sieve is less than 50% by weight, the particle size is 0.05 mm.
Since the number of particles less than the number relatively increases, the amount of fine powder separated in the fine powder classification operation shown below increases, and as a result, the yield in coarse pulverization decreases, which is not preferable.

The carbonaceous material coarsely pulverized as described above is classified so that the proportion of particles having a particle size of 0.05 mm or less is 0.1% by weight or less. 0.1% by weight of particles with particle size of 0.05mm or less in coarsely pulverized carbonaceous material
Examples of the classification method to be as follows include dry or wet classification using a sieve, airflow classification, and the like. In view of the processing speed, secondary contamination, etc., dry classification with a sieve is preferable.

  More specifically, it is desirable to classify the coarsely pulverized carbonaceous matter with a 270 mesh sieve (aperture 53 μm) and remove the under sieve. Classification with the above 60 mesh sieve (aperture 250 μm) can reduce the iron content in the carbonaceous material on the sieve, but is not preferable because the recovery rate of the coarsely pulverized carbonaceous material is reduced. On the other hand, classification with a sieve of 400 mesh (aperture 38 μm) is not preferable because fine powder containing a relatively large amount of iron cannot be sufficiently separated.

By coarsely pulverizing and classifying as described above, a carbonaceous material in which particles having a particle size of 2 mm or more are 0.1 wt% or less and particles having a particle size of 0.05 mm or less is 0.1 wt% or less is obtained. The reason is not clear, but the iron content in the carbonaceous material powder having a particle size of 0.05 mm or less is higher than that in the carbonaceous material powder having a particle size of 0.05 mm or more, thus obtaining a carbonaceous material having a reduced iron content. be able to.

  The carbonaceous material coarsely pulverized and classified as described above is further finely pulverized and then baked, or baked and then finely pulverized to produce a low-temperature fired carbon powder for electrode materials. The conditions for firing and pulverization can be appropriately selected according to the intended use of the low-temperature fired carbon powder.

The method for pulverization is not particularly limited as long as it can be pulverized so that the average particle size of the carbon powder is 1 μm or more and 30 μm or less, and examples thereof include use of a jet mill, a cross flow mill, and a turbo mill.

  The carbonaceous material before or after pulverization is measured at a temperature of 600 ° C. or higher and 1,400 ° C. or lower, preferably 650 ° C. or higher and 1,300 ° C. or lower, in a furnace such as an atmospheric furnace, shuttle furnace, or rotary kiln. Firing (carbonization) for several hours. Further, it is desirable to perform the firing in an inert gas atmosphere such as nitrogen gas or argon gas.

A finely pulverized low-temperature calcined carbon powder is obtained as described above. The carbon powder uses a carbonaceous material that is coarsely pulverized and classified so that particles having a particle size of 0.05 mm or less are 0.1% by weight or less.
Generation of fine powder of less than μm is suppressed, and it can be preferably used as an electrode material.

  The low-temperature calcined carbon powder thus obtained can be further activated or graphitized depending on the purpose of use or the like, and used as an electrode material for a storage battery such as an electric double layer capacitor or a non-aqueous electrolyte secondary battery. For activation or graphitization, a known method can be appropriately used.

In addition, the measurement of the iron content in a carbonaceous material or a carbonized product was performed as follows.
That is, about 4 g of the sample was crushed in a menor mortar, classified with a 60 mesh sieve, and the under sieve was collected. The collected material was incinerated with concentrated sulfuric acid, and metal oxides in the incinerated material were quantitatively analyzed by ICP.

A mixed oil obtained by mixing atmospheric distillation residue oil and fluid catalytic cracking residue oil at a weight ratio of 50:50 is charged into a bench reactor having an internal volume of 20 m ³ and kept at a pressure of about 0.5 Mpa and a temperature of about 500 ° C. for 40 hours. As a result, 10 tons of coke mass was obtained. The obtained coke mass was crushed to a diameter of 10 cm or less with a roll crusher. The iron content in the crushed material was 44 ppm.

10 tons of the carbonaceous material (coke crushed material) was coarsely pulverized by a hammer mill made of SUS304 with a hammer diameter of 500 mm so that particles having a particle diameter of 2 mm or more were 0.1% by weight or less. The coarsely pulverized carbonaceous material was classified with a 60 mesh sieve, and the weight ratio on the sieve was 66% by weight. Further, about 10 tons of coarsely pulverized carbonaceous material was classified with a 270 mesh sieve. The weight ratio on the sieve was 92% by weight. The top of the sieve was collected and the bottom of the sieve was discarded.

About 9 tons of carbonaceous material roughly pulverized as described above, using a rotary kiln (heating method LPG flame, retort inner diameter 40 cm, heating zone 240 cm), fuselage outlet temperature 720 ° C., nitrogen flow rate 20 L / min, transport speed 30 kg / Carbonization was performed under the condition of hr. About 8 tons of the obtained carbide was pulverized using a jet mill (nozzle diameter: 2 mm) under the condition of a processing rate of 200 kg / hr so that the average particle size was 12 μm. Further, the finely pulverized product was classified with an airflow classifier (can body outer diameter 1 m, can body height 2 m) so that the fine powder having a particle size of less than 1 μm was less than 0.1 wt%.

The obtained carbonized product was about 7 tons, and the iron content in the carbonized product was 61 ppm. The fine powder having a particle size of less than 1 μm separated by classification was 12% by weight based on the total amount of the finely pulverized product.

Fine pulverization / classification and carbonization were performed in the same manner as in Example 1 except that about 9 tons of coarsely pulverized carbonaceous material similar to Example 1 was used and the order of carbonization and fine pulverization was changed.
The fine powder having a particle size of less than 1 μm of the carbonaceous material after pulverization and classification was 9% by weight with respect to the total amount of the pulverized product. Further, about 8 tons of finely pulverized product after pulverization and classification was carbonized under the same conditions as in Example 1.

  The obtained carbonized product was about 7 tons, and the iron content in the carbonized product was 66 ppm.

  In Example 1, except that the operating conditions of the rotary kiln were a fuselage outlet temperature of 600 ° C. and a conveyance speed of 60 kg / hr, carbonized products were obtained by carrying out the pulverization, carbonization and fine pulverization / classification treatment in the same manner as in Example 1. Got.

The obtained carbonized product was about 8 tons, the iron content in the carbonized product was 61 ppm, and the fine powder having a particle size of less than 1 μm was 11% by weight based on the total amount of the finely pulverized product.

About 9 tons of coarsely pulverized carbonaceous material similar to that in Example 1 was placed in a rectangular crucible made of alumina (length: 20 cm,
About 4,600 pieces (2 kg per piece) were filled in. One lot of 500 filled rectangular crucibles was stored in a batch-type firing furnace (heating type LPG flame, inner dimensions 400 cm, 300 cm, 200 cm). Ten lots of carbonization were performed under the condition that the indicated value of the thermocouple installed in the center of the furnace was 1,000 ° C and the flow rate of nitrogen was 10 L / min. About 8 tons of the obtained carbide was pulverized using a jet mill (nozzle diameter: 2 mm) under the condition of a processing speed of 100 kg / hr so that the average particle diameter was 15 μm. Further, the finely pulverized product was classified with an airflow classifier (can body outer diameter 1 m, can body height 2 m) so that the fine powder having a particle size of less than 1 μm was less than 0.1 wt%.

The obtained carbonized product was about 7 tons, the iron content in the carbonized product was 56 ppm, and the fine powder having a particle size of less than 1 μm was 15% by weight based on the total amount of the finely pulverized product.

Fine pulverization / classification and carbonization were performed in the same manner as in Example 4 except that the order was changed using about 9 tons of roughly pulverized carbonaceous material similar to that in Example 4.
The fine powder having a particle size of less than 1 μm of the carbonaceous material after pulverization and classification was 9% by weight with respect to the total amount of the pulverized product. Further, the finely pulverized product after pulverization and classification was carbonized under the same conditions as in Example 4.

  The obtained carbonized product was about 7 tons, and the iron content in the carbonized product was 58 ppm.

In Example 4, a carbonized product was obtained by carbonization, pulverization and classification in the same manner as in Example 4 except that the indicated value of the thermocouple of the batch-type firing furnace was 1,400 ° C.
The obtained carbonized product was about 6 tons, the iron content in the carbonized product was 56 ppm, and the fine powder having a particle size of less than 1 μm was 20% by weight based on the total amount of the finely pulverized product.

A coal tar pitch having a quinoline soluble content of 100% by weight was charged into a bench reactor having an internal volume of 20 m ³ and kept at a pressure of about 0.5 MPa and a temperature of about 500 ° C. for 40 hours to obtain 10 tons of coke mass. The obtained coke mass was crushed to a diameter of 10 cm or less with a roll crusher. The iron content in the crushed material was 547 ppm.

About 7 tons of carbonized product was obtained by subjecting 10 tons of the carbonaceous material (coke lump of coke) to ground grinding, carbonization and fine grinding / classification in the same manner as in Example 1.
The iron content in the carbonized product was 618 ppm, and the fine powder having a particle size of less than 1 μm was 13% by weight based on the total amount of the finely pulverized product.

10 tons of the carbonaceous material (coke crushed material) of Example 7 was subjected to ground pulverization, fine pulverization / classification and carbonization in the same manner as in Example 2 to obtain about 7 ton of a carbonized product.
The iron content in the carbonized product was 618 ppm, and the fine powder having a particle size of less than 1 μm was 10% by weight based on the total amount of the finely pulverized product.
[Comparative Example 1]

A carbonized product was obtained by performing the same treatment as in Example 1 except that the coarsely pulverized carbonaceous material of Example 1 was not classified.
The obtained carbonized product was about 7 tons, the iron content in the carbonized product was 484 ppm, and the fine powder having a particle size of less than 1 μm was 22% by weight based on the total amount of the finely pulverized product.
[Comparative Example 2]

A carbonized product was obtained by performing the same treatment as in Example 1 except that the carbonaceous material of Example 1 was not coarsely pulverized.
At that time, the nozzles were frequently clogged in the fine pulverization step, so that coarse particles had to be removed. As a result, the yield of fine grinding was only 30% by weight. The obtained carbonized product was about 2 tons, the iron content in the carbonized product was 50 ppm, and the fine powder having a particle size of less than 1 μm was 12% by weight based on the total amount of the finely pulverized product.
[Comparative Example 3]

A carbonized product was obtained by performing the same treatment as in Example 2 except that the coarsely pulverized carbonaceous material of Example 1 was not classified.
The obtained carbonized product was about 7 tons, the iron content in the carbonized product was 568 ppm, and the fine powder having a particle size of less than 1 μm was 20% by weight based on the total amount of the finely pulverized product.
[Comparative Example 4]

A carbonized product was obtained by performing the same treatment as in Example 4 except that the coarsely pulverized carbonaceous material of Example 1 was not classified.
The obtained carbonized product was about 6 tons, the iron content in the carbonized product was 245 ppm, and the fine powder having a particle size of less than 1 μm was 26% by weight based on the total amount of the finely pulverized product.
[Comparative Example 5]

A carbonized product was obtained by performing the same treatment as in Example 5 except that the coarsely pulverized carbonaceous material of Example 1 was not classified.
The obtained carbonized product was about 7 tons, the iron content in the carbonized product was 225 ppm, and the fine powder having a particle size of less than 1 μm was 22% by weight based on the total amount of the finely pulverized product.
[Comparative Example 6]

A carbonized product was obtained by performing the same treatment as in Example 6 except that the coarsely pulverized carbonaceous material of Example 1 was not classified.
The obtained carbonized product was about 5 tons, the iron content in the carbonized product was 317 ppm, and the fine powder having a particle size of less than 1 μm was 32% by weight based on the total amount of the finely pulverized product.

  The carbonaceous material for electrode material and low-temperature fired carbon powder (carbonized product) comprising coke according to the present invention have a low iron content and a small amount of fine powder generated during production. It can be suitably used as an electrode material for power storage devices such as activated carbon for multilayer capacitors.

Claims (3)

Carbonaceous material made of coke obtained by heat treatment of petroleum-based and / or coal-based heavy oil, using a pulverizer whose hammer is made of austenitic steel, a particle size of 2 mm or more in the coke Coarsely pulverized so that the particles of 0.1% by weight or less, and classified so that particles with a particle size of 0.05mm or less is 0.1% by weight or less,
Furthermore, after pulverizing to an average particle size of 1 μm to 30 μm and then firing at a temperature of 600 ° C. to 1,400 ° C., or firing at a temperature of 600 ° C. to 1,400 ° C., then pulverizing to an average particle size of 1 μm to 30 μm A method for producing a low-temperature calcined carbon powder for an electrode material. An electrode material for a power storage device comprising the low-temperature calcined carbon powder obtained by the production method according to claim 1 . An electrode material for a power storage device, comprising a carbon powder obtained by further activating or graphitizing the low-temperature fired carbon powder obtained by the production method according to claim 1 .