TW202432458A - Manufacturing method for porous carbon support and porous carbon support manufactured by the same - Google Patents

Abstract

The present invention can provide a method for manufacturing a porous carbon support, the method comprising the steps of: (1) subjecting a petroleum-based raw material to pyrolysis and polycondensation to form pitch; (2) solidifying and pelletizing the pitch to obtain solid pitch pellets; (3) stabilizing the solid pitch pellets without pulverization; and (4) carbonizing the stabilized pitch pellets to obtain a carbonized product.

Description

Method for preparing porous carbon carrier and porous carbon carrier prepared thereby

The present invention relates to a method for preparing a porous carbon carrier and a porous carbon carrier prepared by the method.

Carbon materials refer to materials made from carbon, one of the most common resources on earth. Carbon materials are light, strong, and have excellent electrical and thermal conductivity. They are core materials widely used in hydrogen-powered vehicles, aviation, secondary batteries, high-end consumer products, and other fields.

Carbon materials can be made from a variety of raw materials such as coconut shells, polyacrylonitrile, rayon, asphalt, etc. Among them, it is difficult to control the molecular weight and composition of carbon materials made from solid raw materials such as coconut shells (Korean Publication Patent Application No. 10-2019-0093960).

On the other hand, asphalt, a viscoelastic solid polymer extracted from crude oil or plants, has the following advantages: high yield when converted into carbon materials, cheap raw material price, and the ability to reduce the energy required for heat treatment because its molecular structure is closer to graphite structure than other raw materials (U.S. Patents Nos. 4,242,196 and 4,340,464).

In particular, asphalt produced from pyrolysis fuel oil (PFO), naphtha cracking bottom oil (NCB), vacuum residue (VR), fluid catalytic cracking decant oil (FCC-DO), etc., which are obtained as by-products in the petroleum refining process, have high aromatic compound content and low impurity content such as sulfur and nitrogen. Therefore, asphalt produced from them has attracted much attention as a carbon material.

Conventionally, a porous carbon support is prepared by preparing a carbon precursor in the form of pellets from the above-mentioned asphalt, crushing it into a powder form, and then performing an activation process. However, the porous carbon support prepared as described above mainly includes micropores, so when chemical vapor deposition (CVD) or the like is performed in a subsequent process, there is a problem that it cannot be sufficiently deposited into deep pores.

Prior art documents Patent documents (Patent document 0001) Korean published patent application number 10-2019-0093960 (Patent document 0002) U.S. Patent No. 4242196 (Patent document 0003) U.S. Patent No. 4340464

Invent the problem you want to solve

One of the various objects of the present invention is to provide a method for preparing a porous carbon support having controlled pore characteristics and capable of being sufficiently deposited into deep pores during chemical vapor deposition, and a porous carbon support prepared by the preparation method.

One of the multiple objects of the present invention is to provide a method for preparing a porous carbon support capable of preparing a negative electrode material having a high charge and discharge capacity and a porous carbon support prepared by the preparation method.

One of the multiple objects of the present invention is to provide a method for preparing a porous carbon support capable of preparing a negative electrode material with improved cycle characteristics and a porous carbon support prepared by the preparation method.

One of the multiple objects of the present invention is to provide a method for preparing a porous carbon support capable of preparing a negative electrode material having excellent mechanical properties and a porous carbon support prepared by the preparation method.

Technical means to solve the problem

According to an embodiment of the present invention, the present invention can provide a method for preparing a porous carbon carrier, which comprises: step (1), synthesizing asphalt by thermally decomposing and condensing a petroleum-based raw material; step (2), solidifying and granulating the asphalt to obtain solid asphalt particles; step (3), stabilizing the solid asphalt particles without crushing; and step (4), carbonizing the stabilized asphalt particles to obtain a carbonized body.

At this time, the polycondensation temperature of the asphalt synthesis in the above step (1) may be in the range of 350°C or more and/or 500°C or less.

In addition, the asphalt synthesized in the above step (1) may have a softening point of 200°C or higher.

In one embodiment of the present invention, the thickness of the solid asphalt particles in step (3) of the method for preparing the porous carbon carrier according to the present invention can be greater than 1 mm.

In one example, step (3) of the method for preparing a porous carbon carrier according to the present invention may include heating the un-crushed solid asphalt particles to a temperature of 250° C. or above and/or 400° C. or below, and the heating may be performed by microwave or plasma.

On the other hand, the oxygen content of the asphalt particles stabilized in the above step (3) can be 10% by weight or more.

In addition, the distribution deviation of the oxygen content in the cross section of the asphalt particles stabilized in the above step (3) can be 30% or less.

In one embodiment, the method for preparing a porous carbon carrier according to the present invention may further include a step of depositing silicon after the above step (4).

At this time, the deposition may be performed at a temperature of 300° C. or higher and/or 600° C. or lower and in a silane (SiH ₄ ) gas atmosphere of 50 sccm or higher and/or 500 sccm or lower.

In addition, the content of the deposited silicon may be 10 wt % or more relative to the total weight of the porous carbon support.

Other embodiments of the present invention may provide a porous carbon carrier prepared by the above-mentioned preparation method.

Comparison with the efficacy of previous technologies

As one of the various effects of the present invention, a method for preparing a porous carbon support in which silicon is sufficiently deposited in the pores in the deep part by forming mesopores in the outer periphery and micropores in the deep part, and a porous carbon support prepared by the preparation method can be provided.

As one of the various effects of the present invention, a method for producing a porous carbon support capable of producing a negative electrode material having a high charge and discharge capacity and a porous carbon support produced by the production method can be provided.

As one of the various effects of the present invention, a method for preparing a porous carbon support capable of preparing a negative electrode material with improved cycle characteristics and a porous carbon support prepared by the preparation method can be provided.

As one of the various effects of the present invention, a method for preparing a porous carbon support capable of preparing a negative electrode material having excellent mechanical properties and a porous carbon support prepared by the preparation method can be provided.

However, the various advantages and effects of the present invention are not limited to the above contents and can be more easily understood through the process of describing the implementation mode of the present invention.

The following describes the embodiments of the present invention in combination with specific embodiments and drawings. However, the technology described in this specification is not limited to specific embodiments, and should be understood to include various modifications, equivalents and/or alternatives of the embodiments of this specification. In terms of the drawings, similar drawing marks can be used for similar components.

In the drawings, any content that is not necessary for describing the present disclosure will be omitted for clarity, and the thickness is exaggerated for the purpose of clearly showing layers and regions. Like reference numerals in the drawings refer to like elements, and thus their description will be omitted.

In this specification, expressions such as “having”, “can have”, “including” or “can include” refer to the existence of corresponding features (for example, constituent elements such as numbers, functions, actions or parts), and do not exclude the existence of additional features.

In this specification, expressions such as "A or B", "at least one of A or/and B", or "one or more of A or/and B" can include all possible combinations of the items listed together. For example, "A or B", "at least one of A and B", or "at least one of A or B" can all refer to the following situations: (1) at least one A is included; (2) at least one B is included; or (3) at least one A and at least one B are included.

Unless otherwise indicated, all numbers and expressions relating to amounts of ingredients, reaction conditions and the like used in the specification are to be understood as being modified by the term "about".

The present invention relates to a method for preparing a porous carbon carrier. The method for preparing a porous carbon carrier according to an embodiment of the present invention may include: step (1), synthesizing asphalt by thermally decomposing and condensing a petroleum-based raw material; step (2), solidifying and granulating the asphalt to obtain solid asphalt particles; step (3), stabilizing the solid asphalt particles without crushing; and step (4), carbonizing the stabilized asphalt particles to obtain a carbonized body.

In the following, each step of the present invention will be described in detail.

Step (1)

The step (1) of the method for preparing the porous carbon support according to the present invention may be a step of synthesizing asphalt by thermally decomposing and condensing a petroleum-based raw material.

In an embodiment of the present invention, the petroleum-based feedstock may include at least one selected from pyrolyzed fuel oil (PFO), naphtha cracking bottom oil (NCB), ethylene cracker bottom oil (EBO), vacuum residue (VR), deasphalted oil (DAO), atmospheric residue (AR), fluid catalytic cracking decant oil (FCC-DO), residue catalytic cracking decant oil (RFCC-DO) and heavy aromatic oil. In a preferred embodiment of the present invention, the petroleum-based feedstock may include pyrolyzed fuel oil.

In an embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be performed at a temperature of 350°C or more and/or 500°C or less. The thermal decomposition and polycondensation temperature may be 350°C or more, 360°C or more, 370°C or more, 380°C or more, 390°C or more, 400°C or more, 410°C or more, 420°C or more, or 430°C or more, and may be 500°C or less, 490°C or less, 480°C or less, or 470°C or less, but are not limited thereto. When the thermal decomposition and polycondensation temperature satisfies the above range, asphalt containing a large amount of relatively low molecular weight components can be prepared. Furthermore, in the activation process to be described below, the relatively low molecular weight components are first vaporized, so that mesopores can be fully formed in the carbon support. If the thermal decomposition and polycondensation temperature of the petroleum-based raw materials is too low, it is difficult to prepare asphalt that is solid at room temperature. If the above temperature is too high, the asphalt contains a large amount of components with relatively high molecular weight, so it may not be possible to prepare a carbon support with mesopores.

In the embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out in the atmosphere of an oxidizing gas, an inert gas or a mixed gas thereof. In a preferred embodiment of the present invention, the oxidizing gas can be oxygen, ozone or a combination thereof, the inert gas can be nitrogen, helium, neon, argon or a combination thereof, and the mixed gas can be air, but is not particularly limited thereto.

When an oxidizing gas is used in the thermal decomposition and polycondensation of a petroleum-based raw material, asphalt with a high softening point can be prepared, but it is difficult to perform thermal decomposition and polycondensation at a high temperature. When an inert gas is used in the thermal decomposition and polycondensation of a petroleum-based raw material, thermal decomposition and polycondensation can be performed at a high temperature, but it is difficult to prepare asphalt with a relatively high softening point. When a mixed gas of an oxidizing gas and an inert gas is used in the thermal decomposition and polycondensation of a petroleum-based raw material, asphalt with a relatively high softening point can be prepared by performing thermal decomposition and polycondensation at a relatively high temperature.

In an embodiment of the present invention, the gas may be supplied at a flow rate of 10 ml/min to 800 ml/min during the thermal decomposition and polycondensation of the petroleum-based raw material. In a preferred embodiment of the present invention, the gas may be supplied at a flow rate of 100 ml/min to 500 ml/min during the thermal decomposition and polycondensation of the petroleum-based raw material. If the flow rate of the gas is less than 10 ml/min, the yield of asphalt increases, but the low molecular weight components become excessive, which is disadvantageous for subsequent processes (e.g., stabilization). If the flow rate of the gas exceeds 800 ml/min, the yield of asphalt may decrease.

In the embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out for 1 hour to 10 hours. In the preferred embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out for 2 hours to 8 hours. In the more preferred embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out for 2 hours to 7 hours. If the thermal decomposition and polycondensation time of the petroleum-based raw material is less than 1 hour, it is difficult to prepare asphalt with a high softening point. If the thermal decomposition and polycondensation time of the petroleum-based raw material exceeds 10 hours, excessive quinoline insoluble components may be generated.

In the embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out under stirring. There is no particular limitation on the stirring conditions of the petroleum-based raw material, for example, a stirrer rotating at 10 rpm to 500 rpm can be used.

In the embodiment of the present invention, the softening point of the asphalt synthesized in step (1) may be above 200°C. The asphalt prepared in the above step (1) has a high softening point, and when used as a precursor for preparing a carbon support, it is easy to carry out a stabilization process, and a high yield can be obtained after carbonization and activation. The upper limit of the softening point of the above asphalt may be, for example, below 350°C, below 330°C, or below 300°C, but is not limited thereto.

In an embodiment of the present invention, the yield of the asphalt synthesized in step (1) may be 10% to 50% by weight. In another embodiment of the present invention, the yield of the asphalt may be 10% to 40% by weight. In yet another embodiment of the present invention, the yield of the asphalt may be 20% to 30% by weight.

In the process for preparing a porous carbon support from a petroleum-based raw material according to an embodiment of the present invention, a step of pre-treating the petroleum-based raw material may be performed before the above step (1). By removing the low-boiling point components contained in the petroleum-based raw material through the pre-treatment step, asphalt with a higher softening point can be prepared.

In the embodiment of the present invention, the pretreatment step can be carried out at a temperature equal to or lower than the thermal decomposition and polycondensation temperature of the petroleum-based feedstock in step (1), but is not particularly limited to the above conditions. Specifically, the pretreatment step can be carried out at 250°C to 450°C, preferably 250°C to 400°C, and more preferably 300°C to 400°C.

In the embodiment of the present invention, the pretreatment step can be carried out for a time equal to or shorter than the thermal decomposition and polycondensation time of the petroleum-based feedstock in step (1), but is not particularly limited to the above conditions. Specifically, the pretreatment step can be carried out for 1 hour to 8 hours, preferably 1 hour to 6 hours, and more preferably 1 hour to 5 hours.

Step (2)

According to the method for preparing the porous carbon carrier of the present invention, step (2) may be a step of obtaining solid asphalt particles by solidifying and granulating asphalt.

The liquid asphalt obtained in step (1) is granulated into a desired size, for example, by extrusion and cooling to solidify, to obtain solid asphalt granules. The process of obtaining solid asphalt granules by extruding, cooling and solidifying liquid asphalt can be carried out using commercial equipment. For example, the Double belt coolers and flakers of IPCO can be used to perform the above process, but are not particularly limited to the above equipment.

The average particle size of the asphalt particles obtained in step (2) is 3 mm to 30 mm, preferably 5 mm to 25 mm. When the average particle size of the asphalt particles is within the above range, a porous carbon support can be prepared by stabilization, carbonization and activation as described below without the need to pulverize the asphalt particles separately. Therefore, the product yield can be improved by a simple process, and a porous carbon support with controlled pore characteristics can be provided.

Step (3)

The step (3) in the method for preparing the porous carbon support according to the present invention can be a step of stabilizing the solid asphalt particles without crushing them. Specifically, the above step can be a step of stabilizing the structure of asphalt by oxidizing the un-crushed solid asphalt particles once.

In the method for preparing a porous carbon carrier according to the present invention, the solid asphalt particles prepared in the above step (2) may not be crushed. In the past, a carbon precursor in the form of particles was prepared, crushed into a powder form, and then an activation process was performed to prepare a porous carbon carrier. This is because, when the particles are stabilized in an un-crushed state, oxygen does not penetrate into the interior of the particles, and therefore no reaction with oxygen occurs. As a result, the isotropy of the asphalt may not be maintained during the carbonization and activation process, and the interior of the particles may be coked during carbonization, making it difficult for the pores to develop smoothly. However, when the prepared particles are crushed, the process is somewhat complicated, and the yield is reduced during the crushing process. According to the method for preparing the porous carbon carrier of the present invention, the solid asphalt particles prepared in step (2) are stabilized without being crushed, thereby simplifying the process and improving the process efficiency.

In one embodiment of the present invention, the thickness of the solid asphalt particles stabilized in the above step (3) can be greater than 1 mm. For example, the thickness of the above asphalt particles can refer to the shortest length of the length of an imaginary line passing through the center of the asphalt particles. The thickness of the above solid asphalt particles can be greater than 1 mm, greater than 2 mm, or greater than 3 mm, and can be less than 10 mm, less than 9 mm, or less than 8 mm, but is not limited thereto. If the solid asphalt particles stabilized in step (3) are not crushed, the above thickness can be met, and by undergoing the stabilization step described below, a porous carbon carrier having excellent pore characteristics and which can be effectively used for various purposes can be prepared.

In one embodiment of the present invention, the stabilization of the asphalt particles can be performed at a temperature of 250°C or more and/or 400°C or less. The stabilization temperature of the asphalt particles can be 250°C or more, 260°C or more, 270°C or more, or 280°C or more, and can be 400°C or less, 390°C or less, 380°C or less, 370°C or less, 360°C or less, or 350°C or less, but is not limited thereto. When the stabilization temperature of the asphalt particles satisfies the above range, the carbon structure in the asphalt changes from thermoplastic to thermosetting, so that the structure can be stably maintained during the subsequent carbonization process.

At this time, the heating rate may be 0.5°C/min or more and/or 10°C/min or less. The heating rate may be 0.5°C/min or more, 1°C/min or more, or 2°C/min or more, and may be 10°C/min or less, 8°C/min or less, or 6°C/min or less, but is not limited thereto. If the heating rate is too slow, it may not be fully stabilized inside the particles. In addition, if the heating rate is too fast, the reaction time with oxygen is shortened, the temperature rises rapidly, and the asphalt cannot be crosslinked and melts.

In one example, the above-mentioned heating can be performed by microwaves and/or plasma. In the existing method for preparing porous carbon carriers, various methods are used to heat the particles in the stabilization step. As a heating method for the general stabilization step, for example, heating using an electric furnace can be cited, but in the case of this heating method, the heat transfer in the thickness direction is insufficient, so uniform heat treatment may not be achieved. As a result, there may be problems such as asphalt not being stabilized but melting, pores not being developed in the carbonization and activation processes, or structural stabilization of asphalt not being achieved. Therefore, in the existing preparation method, solid asphalt particles are crushed into powder and then stabilized. In contrast, the method for preparing a porous carbon support according to the present invention can heat the asphalt particles from the inside of the asphalt by heating the asphalt particles using microwaves and/or plasma, thereby achieving uniform heating. This promotes the diffusion of oxygen into the inside, and thus, even if the asphalt particles in an un-crushed state are not crushed and immediately stabilized, a porous carbon support having excellent pore characteristics can be prepared.

In the embodiment of the present invention, the stabilization of the asphalt particles can be carried out under a pressure of 0.1 bar to 10 bar, preferably 0.5 bar to 5 bar. When the asphalt particles are stabilized under the above pressure, the carbon structure inside the particles can be fully stabilized.

In the embodiment of the present invention, the stabilization of the asphalt particles can be carried out under the flow conditions of 0.1ml/min to 500ml/min, preferably 1ml/min to 300ml/min of an oxidizing gas, preferably air or oxygen. When the asphalt particles are stabilized under the above-mentioned oxidizing gas flow conditions, the structure of the carbon inside the particles can be fully stabilized.

In the embodiment of the present invention, the stabilization of the asphalt particles can be carried out for 1 to 10 hours, preferably 2 to 8 hours. When the asphalt particles are stabilized within the above time, the carbon structure inside the asphalt can be fully stabilized.

In one example, the oxygen content of the stabilized asphalt particles in step (3) of the method for preparing a porous carbon carrier according to the present invention can be 10 wt% or more relative to the total weight of the asphalt particles. The oxygen content of the stabilized asphalt particles can be a value measured using SEM-EDS. Relative to the total weight of the asphalt particles, the oxygen content of the asphalt particles can be 10 wt% or more, 12 wt% or more, 14 wt% or more, or 15 wt% or more, and can be 30 wt% or less, 28 wt% or less, 26 wt% or less, or 25 wt% or less, but is not limited thereto.

The above-mentioned asphalt particles can be stabilized by heating with microwaves and/or plasma. When the asphalt particles are heated with microwaves and/or plasma, uniform heat treatment can be achieved by heating from the inside of the particles, so the oxygen content of the stabilized asphalt particles can meet the above range. If the oxygen content of the stabilized asphalt particles is too low, melting or coking may occur due to the lack of oxygen that plays a crosslinking role in the carbonization process. In addition, if the oxygen content of the stabilized asphalt particles is too high, overreaction with oxygen may occur, resulting in a reduction in the yield in the carbonization process, and structural development may not be achieved smoothly.

In another example, in step (3) of the method for preparing a porous carbon carrier according to the present invention, the oxygen content distribution deviation in the cross section of the stabilized asphalt particles can be less than 30%. The oxygen content in the cross section of the stabilized asphalt particles can be a value measured by line profiling analysis using SEM-EDS, and the oxygen content distribution deviation (d) can refer to the percentage of the value (|(M-a)|/M)| obtained by dividing the difference (|(M-a)|) of the oxygen content (weight %) value (a) that differs most from the average value (M) of the oxygen content (weight %) measured in the cross section by the average value (M) after calculating the average value (M). The distribution deviation of the oxygen content in the cross section of the asphalt particles stabilized in the above step (3) may be 30% or less, 28% or less, 26% or less, 24% or less, 22% or less, or 20% or less. There is no particular restriction on the lower limit, but for example, it may be 0% or more, greater than 0%, 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, but is not limited thereto.

As described above, the asphalt particles in step (3) of the method for preparing a porous carbon carrier according to the present invention can be stabilized by heating with microwaves and/or plasma in an un-crushed state. When the un-crushed asphalt particles are heated in air using a general electric furnace, the distribution deviation of the oxygen content may increase due to the difference in heating rate between the center and the periphery of the asphalt particles. On the other hand, in the case of the method for preparing a porous carbon carrier according to the present invention, by stabilizing the un-crushed asphalt particles using microwaves and/or plasma, uniform heat treatment can be performed and a low oxygen content deviation can be achieved. If the distribution of oxygen content in the cross section of the asphalt particles stabilized in step (3) deviates too much, the structure of the particles and the pore structure formed thereby may develop unevenly due to the heterogeneity of the oxygen content.

The method of heating the un-crushed asphalt granules with microwaves and/or plasma in the above step (3) is not particularly limited, as long as the above asphalt granules can be sufficiently heated. For example, the asphalt granules can be heated with microwaves having a power in the range of 500 W to 1000 W, but the present invention is not limited thereto. In addition, the above heating can be performed using DC or RF plasma in a vacuum (less than 500 mtorr) or under normal pressure, but the present invention is not limited thereto.

Step (4)

Step (4) in the method for preparing the porous carbon support according to the present invention may be a step of obtaining a carbonized body by carbonizing the stabilized asphalt particles. By carbonizing the asphalt particles, other functional groups contained in the asphalt can be removed to obtain a carbonized body substantially composed of pure carbon.

In the embodiment of the present invention, the carbonization of asphalt can be carried out in an inert gas atmosphere. In the preferred embodiment of the present invention, the carbonization of asphalt can be carried out in a nitrogen or argon atmosphere, but is not particularly limited thereto.

In the embodiment of the present invention, the carbonization of asphalt can be performed at a temperature greater than 700° C. and less than or equal to 1,000° C., preferably at a temperature of 800° C. to 900° C. If the temperature during the carbonization of asphalt is lower than the above range, carbonization may not be fully achieved, and if the temperature during the carbonization of asphalt is higher than the above range, the carbonization yield may decrease.

In the embodiment of the present invention, the carbonization of asphalt can be carried out under the flow conditions of 0.1ml/min to 30ml/min, preferably 0.1ml/min to 10ml/min of oxidizing gas, preferably nitrogen. When the carbonization of asphalt is carried out under the above-mentioned inert gas flow conditions, the asphalt can be fully carbonized.

In the embodiment of the present invention, the carbonization of asphalt can be carried out for 0.5 hours to 5 hours, preferably 1 hour to 3 hours. When the carbonization of asphalt is carried out within the above time, the asphalt can be fully carbonized.

Step (5)

In step (5) of the method for preparing a porous carbon support according to the present invention, the porous carbon support can be obtained by activating the carbide. The porous carbon support can be obtained by activating the carbide (carbonized asphalt) to form pores in asphalt.

In an embodiment of the present invention, the activation of the carbide can be performed in an oxidizing gas atmosphere. In a preferred embodiment of the present invention, the activation of the carbide can be performed in a water vapor atmosphere, but is not particularly limited thereto.

In an embodiment of the present invention, activation of the carbide may be performed at a temperature greater than 700° C. and less than or equal to 1,000° C., preferably at a temperature of 800° C. to 900° C. When activation of the carbide is performed at the above temperature, a porous carbon support having sufficiently formed micropores and mesopores may be obtained.

In the embodiment of the present invention, the activation of the carbonized body can be carried out at a pressure of 0.1 bar to 10 bar, preferably 0.1 bar to 5 bar. When the activation of the carbonized body is carried out at the above pressure, a porous carbon support having micropores and mesopores fully formed can be obtained.

In the embodiment of the present invention, the activation of the carbonized body can be carried out under the flow conditions of 0.1 ml/min to 100 ml/min, preferably 0.1 ml/min to 50 ml/min of the oxidizing gas, preferably water vapor. When the activation of the carbonized body is carried out under the above-mentioned oxidizing gas flow conditions, a porous carbon support having fully formed micropores and mesopores can be obtained.

In the embodiment of the present invention, the activation of the carbonized body can be carried out for 0.5 hours to 5 hours, preferably 1 hour to 3 hours. If the activation of the carbonized body is carried out within the above time, a porous carbon support having fully formed micropores and mesopores can be obtained.

In the embodiment of the present invention, the above steps (4) and (5) can be performed in a heating furnace using microwaves and/or plasma. In the preferred embodiment of the present invention, the above steps (4) and (5) can be performed in a heating furnace using microwaves and/or plasma. The heating furnace using microwaves and/or plasma can increase the temperature of the particles themselves without increasing the temperature of other parts of the heating furnace for the asphalt particles.

In the embodiment of the present invention, the above steps (3) to (5) can be continuously performed in one device. In the preferred embodiment of the present invention, the above steps (3) to (5) can be continuously performed in a rotary kiln, but are not particularly limited to the above device. By continuously performing the stabilization, carbonization and activation of asphalt particles in one device, process optimization can be easily achieved.

In the embodiment of the present invention, the porous carbon carrier obtained in step (5) can be further crushed or pulverized and graded. The porous carbon carrier can be further micronized by crushing or pulverizing, and the particle size distribution of the porous carbon carrier can be uniform by grading. Among them, as the grading, dry grading, wet grading or grading using a sieve can be adopted. By crushing or pulverizing and grading, a porous carbon carrier powder with an average diameter of 1μm to 20μm can be obtained.

In one example of the present invention, the method for preparing a porous carbon support according to the present invention may further include a step of depositing silicon on the prepared porous carbon support.

At this time, the above deposition may be performed at a temperature of 300° C. or higher and/or 600° C. or lower and in a silane (SiH ₄ ) gas atmosphere of 150 sccm or higher and/or 500 sccm or lower. The above deposition may be performed by, for example, chemical vapor deposition (CVD) and performed under normal pressure conditions, but is not limited thereto. Through the above deposition, silicon may be deposited on the surface and inside the pores of the porous carbon support according to the present invention.

The present invention also relates to a porous carbon support. The porous carbon support according to the present invention can be prepared by the above method.

In one example of the present invention, the ratio of the mesopore volume relative to the total pore volume of the porous carbon carrier according to the present invention can be greater than 0.1. The pores of the porous carbon carrier can be divided into micropores with a diameter less than 2 nm, mesopores with a diameter of 2 nm to 50 nm, and macropores with a diameter greater than 50 nm according to their size. The above-mentioned porous carrier has been studied in the direction of increasing the ratio of micropores in order to increase the specific surface area or increasing the ratio of macropores in order to increase the amount of material supported in the pores. However, when there are many micropores, silicon is difficult to deposit inside the pores, resulting in a problem of reduced capacitance. In addition, when there are many macropores, silicon agglomeration may occur, generating stress during repeated charging and discharging processes, which may mechanically damage the negative electrode material.

On the other hand, in the case of mesopores, silicon can be sufficiently deposited deep in the pores when silicon is deposited. According to the porous carbon support of the present invention, by containing mesopores within a predetermined range, a sufficient amount of silicon can be deposited inside the pores of the porous support.

The ratio of the mesopore volume relative to the total pore volume of the porous carbon carrier may be 0.10 or more, 0.12 or more, 0.14 or more, or 0.15 or more, but is not limited thereto. The upper limit of the ratio of the mesopore volume relative to the total pore volume of the porous carbon carrier is not particularly limited, but may be, for example, 1.0 or less or less. When the ratio of the mesopore volume relative to the total pore volume of the porous carbon carrier satisfies the above range, the porous carbon carrier has excellent electrical properties and can also prevent excessive aggregation of silicon, thereby preventing damage caused by volume expansion of silicon.

In one embodiment of the present invention, the tap density of the porous carbon carrier according to the present invention can be less than 0.7g/ml. The tap density of the above-mentioned porous carbon carrier can be a value measured using PT-TD200 (German Pharma Test Company). Specifically, 40ml of the porous carbon carrier is loaded into a measuring cylinder, and the volume is observed once after vibrating 1000 times. Repeat the process of vibrating 1000 times after observation and observing the volume 3 times until the volume is no different from the previous volume, and the tap density can be calculated from the final volume. The tap density of the above-mentioned porous carbon carrier can be less than 0.70g/ml, less than 0.65g/ml, less than 0.60g/ml, less than 0.55g/ml, or can be more than 0.05g/ml or more than 0.1g/ml, but is not limited thereto. If the tap density of the porous carbon support is too low, it may be difficult to control the process during silane vapor deposition, resulting in a reduced yield. In addition, if the tap density of the porous carbon support is too high, it may be difficult to coat uniformly during silane vapor deposition.

In one embodiment of the present invention, the BET specific surface area of the porous carbon support according to the present invention may be in the range of 300 m ² /g or more and/or 3000 m ² /g or less. The BET specific surface area of the porous carbon support may be a value measured using ASAP 2420 (Micromeritics instrument (USA)). Specifically, the BET specific surface area of the porous carbon support may be calculated by BET equation and BJH equation using N2/77K isotherm adsorption results according to ISO9277 after analysis at 300°C for 5 hours. The BET specific surface area of the porous carbon support may be 300 ^m2 /g or more, 400 ^m2 /g or more, 500 ^m2 /g or more, and may be 3000 ^m2 /g or less, 2800 ^m2 /g or less, 2600 m2/g or less, or 2000 ^m2 /g or less ^. /g or less, but not limited thereto. If the BET specific surface area of the porous carbon support is too low, the ratio of macropores may increase, resulting in a decrease in the mechanical strength of the negative electrode material and insufficient effective pores. In addition, if the BET specific surface area of the porous carbon support is too high, the ratio of micropores may increase, and silicon may not be sufficiently deposited in the deep part of the porous carbon support.

In one embodiment of the present invention, the diameter of the porous carbon carrier according to the present invention may be less than 20 μm. The above diameter may refer to the D50 diameter, and may be a value measured using a MICROTRAC S3500 device. Specifically, it may refer to an average value obtained by dispersing the porous carbon carrier in ethanol and performing three particle size analyses. The diameter of the above porous carbon carrier may be less than 20 μm, less than 18 μm, less than 16 μm, less than 14 μm, or less than 12 μm, and may be more than 1 μm, more than 2 μm, more than 3 μm, more than 4 μm, or more than 5 μm, but is not limited thereto. If the diameter of the porous carbon carrier is too small, the interior may be quickly filled with silicon during coating, and then additional coating is performed on the surface, resulting in a thicker surface coating. In this case, degradation may be accelerated during charge and discharge, and agglomeration between materials with small particle sizes may occur when manufacturing electrodes, and the agglomerated parts may deteriorate significantly. In addition, if the diameter of the porous carbon carrier is too large, it may be difficult for silane gas to diffuse into the interior of the porous carbon carrier, making it difficult to form a uniform silicon coating inside the carrier. In addition, if the diameter of the porous carbon carrier is too large, it may be difficult to evenly coat the slurry on the current collector when manufacturing electrodes, so the capacity uniformity may be reduced.

In one example, the porous carbon carrier according to the present invention may include macropores having a diameter exceeding 50 nm. At this time, the ratio of the macropore volume relative to the total pore volume of the above-mentioned porous carbon carrier may be 0.4 or less. The ratio of the macropore volume relative to the total pore volume of the above-mentioned porous carbon carrier may be 0.40 or less, 0.38 or less, 0.36 or less, 0.34 or less, 0.32 or less or 0.30 or less, but is not limited thereto. There is no particular restriction on the lower limit of the ratio of the macropore volume relative to the total pore volume of the above-mentioned porous carbon carrier, but for example, it may be greater than 0 or greater than 0. If the macropore ratio of the porous carbon carrier is too high, the mechanical strength of the negative electrode material made of the above-mentioned porous carbon carrier may be reduced. In addition, localized silicon aggregation may occur inside the negative electrode material, which may cause stress due to volume expansion during repeated charge and discharge, leading to damage to the negative electrode material.

In one example, silicon can be arranged on the surface and inside the pores of the porous carbon support according to the present invention. The above silicon can be formed by vapor deposition as described above. Since the porous carbon support according to the present invention has the above structure, the negative electrode material made of the porous carbon support according to the present invention can have a high capacitance while minimizing the effect caused by the volume expansion of silicon.

In another example, the content of the deposited silicon may be greater than 10 wt % relative to the total weight of the particles. The content of the deposited silicon may be a value obtained by energy dispersive spectrometer (EDS) analysis. The content of the deposited silicon may be greater than 10 wt %, greater than 15 wt %, greater than 20 wt %, greater than 25 wt % or greater than 30 wt %, but is not limited thereto. In addition, the content of the deposited silicon may be less than 60 wt %, less than 58 wt %, less than 56 wt %, less than 54 wt %, less than 52 wt % or less than 50 wt %, but is not limited thereto. If the content of the deposited silicon is too low, the capacitance may decrease. In addition, if the silicon content is too high, it will not be able to solve the problem caused by the volume expansion of silicon during charging and discharging, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

The present invention also relates to a battery negative electrode material comprising the porous carbon carrier. The battery negative electrode material comprising the porous carbon carrier according to the present invention can have high capacity, excellent cycle characteristics and improved mechanical strength.

There is no particular limitation on the manufacturing method of the above-mentioned battery negative electrode material, and a conventional manufacturing method of a battery negative electrode material can be used. For example, the above-mentioned battery negative electrode material can be manufactured by mixing a porous carbon carrier, an active material, a conductive material, and a binder, and coating/drying/rolling the mixture on a component such as an electrode current collector, but is not limited thereto.

The present invention also relates to a battery comprising the above-mentioned battery negative electrode material. The battery comprising the battery negative electrode material according to the present invention can be a lithium ion battery or a full solid-state battery, but is not limited thereto.

Specifically, the lithium ion battery may include a positive electrode, a negative electrode, a separator and an electrolyte. In this case, the negative electrode may include the battery negative electrode material. The positive electrode may be made of a material that can be used for a lithium ion battery, for example, it may include at least one positive electrode active material selected from doped or undoped lithium nickel oxide, lithium cobalt oxide, lithium cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide and lithium nickel cobalt aluminum oxide and a positive electrode current collector selected from aluminum, stainless steel, nickel, titanium, platinum or an alloy thereof, but is not limited thereto. In addition, the separator may be a conventional separator that can be used for a lithium ion battery. For example, the diaphragm may include at least one selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE), but is not limited thereto.

The negative electrode of the lithium ion battery may include the negative electrode material of the battery. The negative electrode may include a negative electrode current collector and a negative electrode material of the battery. The negative electrode current collector may include at least one selected from aluminum, stainless steel, nickel, titanium, platinum or an alloy thereof, but is not limited thereto.

The electrolyte of the lithium ion battery may include an organic liquid electrolyte, an inorganic liquid electrolyte, a polymer electrolyte or a molten inorganic electrolyte that can be used in a lithium ion battery, but is not limited thereto.

Specifically, the all-solid battery may include a positive electrode, a negative electrode and a solid electrolyte, and may further include a separator as required, but is not limited thereto. The positive electrode may include the positive electrode active material, and may include a positive electrode current collector as required, but is not limited thereto.

The negative electrode may include the battery negative electrode material according to the present invention. The negative electrode may have a single-layer structure including the battery negative electrode material, or may further include a negative electrode current collector as needed, but is not limited thereto.

The solid electrolyte may be any solid electrolyte that can be used in a fully solid battery. For example, the solid electrolyte may be at least one selected from the group consisting of garnet, Nasicon, LISICON, perovskite, and LiPON, but is not limited thereto.

Hereinafter, preferred embodiments are proposed to help understand the present invention. However, the following embodiments are provided to make it easier to understand the present invention, and the content of the present invention is not limited to the following embodiments.

Preparation Example 1: Preparation of porous carbon support

300 g of petroleum residue oil (YNCC, HTC PFO (pyrolysis fuel oil)) was placed in a reactor equipped with a stirrer, and thermal decomposition and polycondensation were performed at 450°C for 3 hours while nitrogen was supplied at a flow rate of 100 ml/min. At this time, the stirrer was rotated at a speed of 200 rpm to mix the reactants. The polymerized asphalt was solidified and granulated to obtain solid asphalt granules with a thickness of 3.0 mm.

The solid asphalt particles obtained above were placed in a rotary kiln using a plasma with a power of 200 W and stabilized, carbonized and activated in sequence. The conditions for stabilization, carbonization and activation are shown in Table 1 below.

The activated carbonized body after the activation was pulverized using a pulverizer (Netsch Company, Air Jet Mill) to prepare a porous carbon support.

Table 1 Steps condition Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Stabilization Temperature (℃) 320 320 320 320 Time (hours) 2 2 2 2 Atmosphere Air Air Air Air Heat source Plasma (200W) Microwave (800W) Electric heating Electric heating Carbonization Temperature (℃) 900 900 900 900 Time (hours) 1 1 1 1 Atmosphere Nitrogen Nitrogen Nitrogen Nitrogen activation Temperature (℃) 900 900 900 900 Time (hours) 3 3 3 3 Water vapor flow rate (ml/min) 10 10 10 10

Preparation Example 2

A porous carbon support was prepared in the same manner as in Preparation Example 1, except that the thickness of the asphalt particles was changed as shown in Table 2 below and microwaves with a power of 800 W were used instead of plasma for heating in the stabilization step.

Preparation Example 3

A porous carbon support was prepared in the same manner as in Preparation Example 1, except that the thickness of the asphalt particles was changed as shown in Table 2 below and a general electric furnace was used instead of plasma for heating in the stabilization step.

Preparation Example 4

A porous carbon support was prepared in the same manner as in Preparation Example 1, except that the prepared solid asphalt particles were crushed to obtain a powder having a thickness of 200 μm and then heated in a general electric furnace instead of plasma in the stabilization step.

Table 2 Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 thickness 3.0mm 2.1mm 2.0mm 200μm

Table 3 below shows the results of measuring the physical properties of the prepared porous carbon carrier. The specific surface area of the porous carbon carrier was measured using Belsorp mini II according to ASTM D4820-93. The tap density of the carbon carrier was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. The average particle size of the carbon carrier was measured using a particle size analyzer (Horiba, laser particle size analyzer, LA-960V2) according to ASTM E112. The oxygen content and internal deviation were measured by spectral profile analysis using SEM-EDS on the cut surface of the asphalt immediately after stabilization.

Table 3 Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Average particle size (μm) 10.22 7.20 10.45 9.21 Specific surface area (m ² /g) 1285.9 944.2 254.6 1240.9 Total pore volume (cm ³ /g) 0.50 0.40 0.13 0.43 Tap density (g/ml) 0.41 0.52 0.61 0.59 Micropores (%) 42.1 72.9 53.3 72.8 Mesopore (%) 51.6 24.1 45.4 25.1 Average oxygen content (weight %) 17.3 15.6 4.7 18.8 Maximum deviation of oxygen content (weight %) 2.5 2.2 2.0 1.4 Oxygen content distribution deviation (%) 14.5 14.1 42.6 7.4

FIG1 is a SEM image of a cross section of asphalt just after stabilization in Preparation Example 1, and FIG2 is a SEM image of a cross section of asphalt just after stabilization in Preparation Example 3. As shown in FIG1 and FIG2, the oxygen content is measured by performing a spectral profile analysis along a line passing through the center of the cross section of the asphalt.

In Table 3 above, the maximum deviation of the oxygen content (a) is the value of the oxygen content that differs most from the average oxygen content (M), for example, in the case of Preparation Example 1, the oxygen content in the cross section of the porous carbon support may be in the range of 17.3±2.5, that is, in the range of 14.8 to 19.8. In this case, the distribution deviation of the oxygen content may refer to a percentage of (|(14.8-17.3)|/17.3).

Example 1: Preparation of carbon-silicon composite particles

Carbon-silicon composite particles were prepared using the porous carbon support prepared in Preparation Example 1. 15 g to 20 g of the porous carbon support powder of Preparation Example 1 was added to a rotary kiln, and silane (SiH ₄ ) gas was injected to coat the porous carbon support.

The silane gas coating was carried out under normal pressure, at a temperature of 475°C and a flow rate of 300 sccm for 1 hour.

Embodiment 2

Carbon-silicon composite particles were prepared in the same manner as in Example 1, except that the porous carbon support prepared in Preparation Example 2 was used.

Comparison Example 1

Carbon-silicon composite particles were prepared in the same manner as in Example 1, except that the porous carbon support prepared in Preparation Example 3 was used.

Comparative Example 1

Carbon-silicon composite particles were prepared in the same manner as in Example 1, except that the porous carbon support prepared in Preparation Example 4 was used.

Table 4 Embodiment 1 Embodiment 2 Comparative Example 1 Physical properties of carbon support after coating Average particle size (μm) 10.6 11.0 16.7 Specific surface area (m ² /g) 33.4 1.27 1.28 Tap density (g/ml) 0.61 0.60 0.63 Silicon content (wt%) 33.9 39.7 32.0

Table 4 above shows the physical properties measured after silicon was deposited on the porous carbon support in Examples 1 and 2 and Comparative Example 1. In Comparative Example 1, the specific surface area was too low, and it seemed that no pores were formed toward the inside, so silicon could not be coated inside the pores. Referring to Table 4, it can be seen that the silicon content of Examples 1 and 2 and Comparative Example 1 exceeded 30% by weight. From the above results, it can be confirmed that by using the method for preparing a porous carbon support according to the present invention, composite particles with a sufficient amount of silicon deposited can be prepared even without pulverizing solid asphalt particles.

Experimental example: Electrochemical evaluation of secondary batteries

Semi-button batteries were fabricated using the prepared carbon-silicon composite particles.

The carbon-silicon composite particles of the embodiment and the comparative example: the conductive material: the binder were mixed at a ratio of 8:1:1 to prepare a slurry. At this time, super-P was used as the conductive material, and a mixture of styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) at a weight ratio of 5:5 was used as the binder.

The slurry was uniformly coated on a copper foil and first dried in an oven at 80°C for about 1 hour. After the primary drying, it was rolled and then secondary dried in a vacuum oven at 120°C for about 6 hours and 30 minutes to produce a negative plate.

A semi-button cell was manufactured using the above-prepared negative electrode plate and a lithium foil as a counter electrode. A porous polyethylene film was used as a separator and a CR2032 semi-button cell was manufactured under the conditions shown in Table 5 below.

As an electrolyte, 10 wt% of fluoro-ethylene carbonate (FEC), 0.2 wt% of lithium tetrafluoroborate (LiBF 4 ), 0.5 wt% of vinylene carbonate (VC) and 1 wt% of propane sultone (PS) additive were dissolved in a solution of 1.3 M LiPF6 in a solvent of 3: ₅ :2 by volume.

Table 5 Composition (AM:CM:BM) 8:1:1 Area capacity (mAh/cm ² ) 1 Electrolyte 1.3 M LiPF ₆ EC/EMC/DMC 3:5:2, FEC 10%, LiBF ₄ 0.2%, 0.5% VC, 1% PS Cut-off voltage (V) Formation: 0.005-1.5V, Cycle Test: 0.005-1.2V C ratio (C) Formation: 0.1-0.1, 0.01C cutoff at 0.005V (CV)

In Table 5 above, AM, CM and BM represent active material (porous carbon support with silane deposited), conductor (Super P carbon black) and binder (styrene-butadiene rubber/carboxymethyl cellulose 5:5), respectively; EC, EMC, DMC, FEC, VC, PS represent ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, fluoroethylene carbonate, vinylene carbonate, propane sultone, respectively.

Electrochemical analysis of the manufactured semi-button cells was performed under the following conditions.

Cut-off voltage (V): 0.005–1.5 V (forming), 0.005–1.2 V (cycling)

Formation rate of C (C): 0.1C for lithiumation, 0.1C for delithiation

Cyclic C rate (C): 0.5C for lithiumation, 0.5C for lithium removal

Table 6 Charging capacity (mAh/g) Discharge capacity (mAh/g) ICE (%) Embodiment 1 2110 1916 90.8 Embodiment 2 2050 1873 91.4 Comparative Example 1 2128 1922 90.3

As shown in the graph shown in FIG3 , the above-mentioned charge and discharge capacity characteristics are measured by taking the capacity in the state where charging is completed as the charge capacity and taking the capacity in the state where discharging starts as the discharge capacity. The above-mentioned ICE is the value of the discharge capacity divided by the charge capacity. Referring to Table 6 above, the semi-button batteries manufactured using Examples 1 and 2 and the semi-button batteries manufactured using Comparative Example 1 have almost the same level of performance in terms of the measurement results of charge capacity, discharge capacity and ICE. Examples 1 and 2 use a porous carbon carrier that is stabilized without crushing the solid asphalt particles in step (3), while Comparative Example 1 uses a porous carbon carrier that is stabilized after crushing the solid asphalt particles using an existing preparation method. In view of the above, by using the method for preparing a porous carbon support according to the present invention, a porous carbon support having excellent pore characteristics can be prepared even without performing a separate pulverization process on solid asphalt particles. Thus, the process efficiency can be greatly improved by the method for preparing a porous carbon support according to the present invention.

Although the embodiments of the present invention have been described in detail above, the present invention is limited by the scope of the patent application, and is not limited to the above embodiments and drawings. Therefore, within the scope of the technical concept of the present invention described in the patent application, a person skilled in the art can perform various substitutions, deformations and changes, and this belongs to the scope of the present invention.

without

FIG1 is a SEM image of a cross section of asphalt just after stabilization in Preparation Example 1. FIG2 is a SEM image of a cross section of asphalt just after stabilization in Preparation Example 3. FIG3 is a graph showing the results of electrochemical evaluation of semi-button cells made using the porous carbon carriers of Example 1 and Comparative Example 1, respectively.

Claims (12)

A method for preparing a porous carbon carrier comprises: Step (1), synthesizing asphalt by thermally decomposing and condensing a petroleum-based raw material; Step (2), solidifying and granulating the asphalt to obtain solid asphalt particles; Step (3), stabilizing the solid asphalt particles without crushing; and Step (4), carbonizing the stabilized asphalt particles to obtain a carbonized body. The method for preparing a porous carbon carrier as described in claim 1, wherein the condensation temperature of the asphalt synthesis in the above step (1) is in the range of above 350°C and/or below 500°C. A method for preparing a porous carbon carrier as described in claim 1, wherein the softening point of the asphalt synthesized in the above step (1) is above 200°C. A method for preparing a porous carbon carrier as described in claim 1, wherein the thickness of the solid asphalt particles in the step (3) is greater than 1 mm. The method for preparing a porous carbon carrier as described in claim 1, wherein the above-mentioned step (3) includes the step of heating the un-crushed solid asphalt particles to a temperature of 250°C or above and/or 400°C or below, and the above-mentioned heating is performed by microwave or plasma. A method for preparing a porous carbon carrier as described in claim 1, wherein the oxygen content of the asphalt particles stabilized in the above step (3) is greater than 10% by weight. A method for preparing a porous carbon carrier as described in claim 1, wherein the distribution deviation of the oxygen content in the cross section of the asphalt particles stabilized in the above step (3) is less than 30%. A method for preparing a porous carbon carrier as described in claim 1, wherein the step of depositing silicon is further included after step (4). The method for preparing a porous carbon support as claimed in claim 8, wherein the deposition is performed at a temperature of 300° C. or higher and/or 600° C. or lower and in a silane (SiH ₄ ) gas atmosphere of 50 sccm or higher and/or 500 sccm or lower. A method for preparing a porous carbon carrier as described in claim 8, wherein the content of the deposited silicon is greater than 10 wt % relative to the total weight of the porous carbon carrier. A porous carbon support, wherein the porous carbon support is prepared by the preparation method as described in any one of claims 1 to 10. A battery negative electrode material includes the porous carbon carrier as described in claim 11.