KR100345297B1 - Method for producing particulate carbon - Google Patents

Abstract

The present invention relates to a method for producing a particulate carbon body, the object of which is to increase the degree of crystallinity by performing a secondary heat treatment of the main raw material composed of an isotropic pitch and a thermosetting resin at low temperature, thereby increasing the crystallinity of the narrow surface spacing of carbon An object of the present invention is to provide a method for producing particles in high yield.

In order to achieve the above object, the present invention provides a method for producing a particulate carbon body, comprising the steps of preparing a molten mixture by weight, using 60-90% isotropic pitch and 10-40% thermosetting resin; Adding a zirconium compound or a boron compound to the molten mixture so that the content of the final carbide becomes 500 ppm-1% and performing a first heat treatment at an inert atmosphere at 450-500 ° C; Performing a second heat treatment at 500-1000 ° C. to obtain a carbon body; And a step of grinding the obtained carbon body to have a particle size distribution of 1-35 μm.

Description

Method for producing particulate carbon

The present invention relates to a method for producing particulate carbon bodies used as carbon anode materials for lithium ion batteries, and more particularly, to a method for producing particulate carbon bodies with high yield using isotropic pitch and thermosetting resin as main raw materials. It is about.

Carbon materials for lithium ion batteries generally use particulate matter or spherical carbon particles (MCMB) obtained by pulverizing bulk carbon materials, and the content of carbon elements is 95% or more and should be chemically stable. In other words, the chemical instability of the carbon material has a high reactivity such as an organic compound or an electrolytic material because the carbon material is used as a negative electrode material for a lithium ion battery, which directly affects the characteristics of the product and thus makes it impossible to maintain a stable quality of the product. The chemical reactivity with and should be low.

In addition, the carbonaceous material for batteries has important properties such as particle size distribution, density, crystallinity, surface properties, etc. of the carbonaceous material as the above chemical properties, and these physical properties vary depending on the raw material and manufacturing conditions of the carbonaceous material. Is common. The carbon electrode material for a lithium ion battery has a smaller particle size and a better uniformity, but is not suitable when the particle size of the lithium ion battery is too small or too large.

Among the methods for manufacturing carbon anode materials known to date, a method for producing a carbon cathode material using a thermosetting resin as a raw material is made of thermosetting resin only in the form of particles (Japan, Japanese Patent Laid-Open No. 62-23431), and thermally cured to a predetermined size. There is a method of producing amorphous carbon particles by pulverizing and firing and graphitizing.

However, the above method can produce only amorphous carbon particles of a certain standard, so that even if the graphitization treatment at 2800 ° C., only the amorphous carbon having a crystallinity (d ₂ ) of the crystallite of the carbon material manufactured is 3.45 kPa or more. Therefore, there is a problem that the performance is not excellent compared to the high manufacturing cost.

Accordingly, the present inventors have repeatedly conducted research and experiments to solve the above problems, and propose the present invention based on the results. The present invention performs secondary heat treatment at a low temperature on a main raw material composed of an isotropic pitch and a thermosetting resin. By increasing the degree of crystallinity, it is intended to provide a method for producing carbon particles having a narrow range of crystallites in a high yield, an object thereof.

1 is a polarized light micrograph of the crystalline carbon body

2 is a scanning electron micrograph of the particulate carbon body

In order to achieve the above object, the present invention provides a method for producing a particulate carbon body, comprising the steps of preparing a molten mixture by weight, using 60-90% isotropic pitch and 10-40% thermosetting resin; Adding a zirconium compound or a boron compound to the molten mixture so that the content of the final carbide becomes 500 ppm-1% and performing a first heat treatment at an inert atmosphere at 450-500 ° C; Performing a second heat treatment at 500-1000 ° C. to obtain a carbon body; And pulverizing the obtained carbon body so as to have a particle size distribution of 1-35 μm.

Hereinafter, the present invention will be described in detail.

First, in the present invention, a melt mixture is prepared using 60-90% isotropic pitch and 10-40% thermosetting resin.

The isotropic pitch and the thermosetting resin may be used as a conventional one, but in the case of the isotropic pitch, it is more preferable to use a melting temperature higher than 110 ° C, such as coal tar pitch or petroleum heavy oil residue, and the thermosetting resin is a phenol resin. It is more advantageous to use inexpensive general purpose resins such as furan resins and polyimide resins.

The isotropic pitch not only forms a digraphitizable carbon similar to the graphite structure by heat treatment, but is also known to exhibit characteristics similar to that of natural graphite by the graphitization treatment, but there is a problem that a high temperature treatment of 2800 ° C or more is required. In addition, the pitch is not only used as a raw material for producing a crystalline carbon body, but the spherical carbon body (MCMB) prepared therefrom is well known as having a very excellent characteristics as a negative electrode material of a lithium ion battery, but the manufacturing process If difficult, the manufacturing cost is expensive.

The thermosetting resin is not only commonly used for preparing amorphous carbon bodies but is also known to be easy to manufacture and has excellent characteristics as a negative electrode material of a lithium ion battery. However, the thermosetting resin has a problem of rapidly deteriorating with repeated charge and discharge. have.

However, the mixed material of the isotropic pitch and the thermosetting resin has an advantage that the chemical composition and characteristics can be expressed in various ways from amorphous to crystalline according to the mixing ratio.

If the amount of the thermosetting resin is less than 10wt%, its addition effect is insignificant, and if it exceeds 40wt%, it is difficult to obtain a carbon body having an anisotropic structure. Therefore, in order to control the crystal structure of the final carbon body, it is preferable to use the thermosetting resin in the range of 10-40 wt% and the isotropic pitch in the range of 60-90 wt% to obtain a molten mixture.

Next, in the present invention, the zirconium compound or the boron compound is added to the molten mixture so that the content of the final carbide is 500 ppm-1% or less, and the first heat treatment is performed at an inert atmosphere of 450-500 ° C.

In the primary heat treatment, a zirconium compound or a boron compound is added to improve electrical characteristics of the low temperature heat treated carbon body. At this time, the zirconium compound or the boron compound is not particularly limited, but in order to obtain more excellent physical properties, it is preferable to use alkoxides.

The zirconium compound or the boron compound is added so that the content of the final carbide to obtain the content is less than 500ppm-1%, if less than 500ppm the addition effect is insignificant, if more than 1% to act as impurities to reduce the adverse effect Because it can.

The zirconium compound or the boron compound-added mixture is preferably subjected to a primary heat treatment to a temperature at which the isotropic pitch, which is the raw material used, can be solidified, and the temperature is about 450-500 ° C. in numerical value. When the primary heat treatment is less than 450 ℃ takes a long time to carbonize to produce a carbon element of more than 90wt% carbon element, when the temperature is above 500 ℃ overlap with the second heat treatment after the process Since there is a region to be produced, the manufacturing cost is increased.

This primary heat treatment is preferably carried out by heating up to 450-500 ° C. at a rate of 3 ° C./min or less, which has the advantage of being able to perform continuous operations leading to secondary heat treatment while giving sufficient time for reaction. Because.

Next, in this invention, a carbon body is obtained by performing secondary heat processing at 500-1000 degreeC, and the obtained carbon body is grind | pulverized.

The secondary heat treatment overlaps with the primary heat treatment at less than 500 ° C., meaning no secondary heat treatment. When the secondary heat treatment is over 1000 ° C., the second heat treatment consumes too much energy and takes too much time to raise the temperature. Accordingly, the secondary heat treatment is preferably 500-1000 ° C, most preferably about 750 ° C.

In the preferred example of the secondary heat treatment, it is more preferable that the temperature of the second heat treatment is increased to a temperature of 5 ° C./min or more to improve the development of the anisotropic structure. In addition, the secondary heat treatment is preferably performed so that the content of carbon atoms is 94% or more.

It is preferable that the obtained carbon body controls the particle size according to a desired use. For example, in order to use as a negative electrode material for a lithium ion battery, it is desirable to have a particle size distribution of 1-35 μm, because when the powder particles are smaller than 1 μm or larger than 35 μm, the characteristics of the electrode material are deteriorated. In order to use the pulverized granular carbon body as a negative electrode material for a lithium ion battery, it is preferable to control so that the interplanar spacing of crystallites may be larger than 3.354 kV and smaller than 3.65 kPa.

When the carbon body is manufactured according to the above-described manufacturing method, a particulate carbon body having excellent physical properties can be obtained in high yield without undergoing graphitization treatment performed at a high temperature.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

The coal tar pitch, which is a solid isotropic pitch, and the phenol resin, which is a solid thermosetting resin, were mixed in the ratio as shown in Table 1 below. Then, the mixture was heated and melted and stirred to uniformly mix in the molten phase, and the mixture was zirconium alkoxide and boron. The first heat treatment was carried out in an inert atmosphere up to 500 ° C with or without the addition of alkoxide and silicon alkoxide to the final carbide content of about 0.5%. The first heat treatment product was heated to 750 ° C. at a temperature increase rate of 5 ° C. per minute, followed by a second heat treatment to maintain carbide for a predetermined time to produce carbide. The obtained carbide was ground using a rotary mill, and after completion of the milling, classified into 25 μm or less using a vibratory classifier to prepare particulate carbon bodies.

The prepared carbonaceous particles were examined using a polarizing microscope and a scanning electron microscope, and the results are shown in Table 1 by investigating physicochemical and electrical properties. In this case, microscopic observation pictures of the particulate carbon bodies corresponding to Inventive Example 2 in Table 1 are shown in FIGS. 1 and 2, where FIG. 1 is a polarized light micrograph of the crystalline carbon bodies, and FIG. 2 is a scanning electron microscope of the particulate carbon bodies. It is a photograph.

Pitch (wt%) Resin (wt%) Primary heat treatment condition (℃ -hr) Secondary heat treatment condition (℃ -hr) additive Specific surface area (㎡ / g) Plane clearance yield(%) Inventive Example 1 70 30 500-2 750-1 B alkoxide 8.00 3.503 94.6 Inventive Example 2 70 30 500-2 750-1 Zr alkoxide 7.22 3.437 95.4 Comparative Example 1 70 30 500-2 750-1 Si alkoxide 2.51 3.576 95.2 Comparative Example 2 40 60 500-2 750-1 - 4.85 3.659 95.3 Comparative Example 3 50 50 500-2 750-1 - 5.49 3.590 95.9 Comparative Example 4 70 30 500-2 750-1 - 4.13 3.586 96.0

By analyzing Table 1 and FIGS. 1 and 2, the following analysis results were obtained.

That is, the carbon body (Comparative Example 1-4) prepared at 750 ° C. with a pitch content of less than 60 wt% or without addition of B alkoxide or Zr alkoxide showed a relatively high value of 3.576-3.659 mm in surface clearance. Rather, the specific surface area was also very low, less than six. This shows that the manufacturing conditions are inadequate as values that do not satisfy the required characteristics as the negative electrode material.

On the contrary, the carbon body prepared by heat treatment at 750 ° C. after addition of B alkoxide or Zr alkoxide using an isotropic pitch of 60 wt% or more (Invention Example 1-2) was fixed even though the heat treatment was performed at low temperature compared with the conventional one. Carbon content (FC), specific surface area and surface gap satisfy well the required characteristics as a negative electrode material of a lithium ion battery.

According to the present invention as described above, it is possible to control the characteristics of the particulate carbon body according to the mixing ratio of the isotropic pitch and the thermosetting resin, which is a raw material to be used and the addition of additives, and to produce carbon particles having excellent properties in high yield. can do.

Claims (3)

In the method of manufacturing a particulate carbon body, Preparing a melt mixture by weight, using 60-90% isotropic pitch and 10-40% thermosetting resin; Adding a zirconium compound or a boron compound to the molten mixture so that the content of the final carbide becomes 500 ppm-1% and performing a first heat treatment at an inert atmosphere at 450-500 ° C; Performing a second heat treatment at 500-1000 ° C. to obtain a carbon body; And Pulverizing the obtained carbon body so as to have a particle size distribution of 1-35 μm; The method of claim 1, The isotropic pitch is coal tar pitch or petroleum heavy oil residue, the melting method of the particulate carbon body characterized in that the melting temperature is higher than 110 ℃ The method of claim 1, The thermosetting resin is a manufacturing method of the particulate carbon body, characterized in that selected from phenol resin, furan resin, polyimide resin