Method for producing porous carbon material

Abstract

The present invention relates to a method for producing a porous carbon material with controlled particle size, which includes a step of pulverizing a porous carbon material using a centrifugal grinder and sieving it through a sieve with an opening size 2.8 to 4 times the particle size D of the target porous carbon material. 50 ​

Description

Technical Field

[0001] The present invention relates to a method for producing a porous carbon material. Specifically, it relates to a method for producing a porous carbon material with controlled particle size. More specifically, the present invention relates to a sulfur-carbon composite containing the porous carbon material and a lithium-sulfur battery containing the same.

[0002] This application claims priority based on Korean Patent Application Nos. 10-2022-0159965 filed on November 25, 2022, 10-2022-0183586 and 10-2022-0183771 filed on December 23, 2022, 10-2022-0185613 filed on December 27, 2022, 10-2023-0063394 filed on May 16, 2023, 10-2023-0070299 filed on May 31, 2023, 10-2023-0073163 filed on June 7, 2023, and 10-2023-0075765 filed on June 13, 2023, and the contents disclosed in the specifications and drawings of the applications are all incorporated into this application.

Background Art

[0003] In recent years, interest in energy storage technology has been increasing. As the application fields expand to include the energy of mobile phones, camcorders, notebook PCs, and even electric vehicles, research and development of electrochemical devices have been actively progressing.

[0004] Electrochemical devices are the most prominent fields in this regard, and among them, the development of rechargeable secondary batteries has become the focus of interest. Recently, in order to improve the capacity density and specific energy in the development of such batteries, it has led to research and development related to new electrode and battery designs.

[0005] Among the currently applicable secondary batteries, lithium secondary batteries developed in the early 1990s have attracted attention due to their higher operating voltage and much higher energy density compared to conventional batteries such as Ni-MH, Ni-Cd, and lead-sulfate batteries that use water-soluble electrolytes.

[0006] In particular, a lithium-sulfur battery is a secondary battery that uses a sulfur-based material having an S-S bond (sulfur-sulfur bond) as a positive electrode active material and lithium metal as a negative electrode active material. Sulfur, which is the main material of the positive electrode active material, has the advantages of being rich in resources, non-toxic, and having a low weight per atom. In addition, the theoretical discharge capacity of a lithium-sulfur battery is 1675 mAh / g-sulfur, and the theoretical energy density is 2,600 Wh / kg, which is much higher than the theoretical energy density of other battery systems currently under research (Ni-MH battery: 450 Wh / kg, Li-FeS battery: 480 Wh / kg, Li-MnO2 battery: 1,000 Wh / kg, Na-S battery: 800 Wh / kg). Therefore, it can be said that it is the most promising battery among the batteries developed so far.

[0007] During the discharge reaction of a lithium-sulfur battery, an oxidation reaction of lithium occurs at the negative electrode, and a reduction reaction of sulfur occurs at the positive electrode. Sulfur before discharge has a cyclic S8 structure. During the reduction reaction (discharge), the S-S bond breaks while the oxidation number of S decreases, and during the oxidation reaction (charging), the S-S bond is further formed while the oxidation number of S increases. Electrical energy is stored and generated using such an oxidation-reduction reaction. During such a reaction, sulfur is converted from cyclic S8 to linear-structured lithium polysulfide (Lithium polysulfide, Li2S x , 1 ≤ x ≤ 8) by a reduction reaction. When such lithium polysulfide is completely reduced, lithium sulfide (Lithium sulfide, Li2S) is finally generated. The discharge behavior of a lithium-sulfur battery is characterized by showing a discharge voltage stepwise, which is different from that of a lithium-ion battery, during the process of being reduced to each lithium polysulfide.

[0008] In order for the lithium-sulfur battery to have an energy density and a life characteristic at a commercially viable level, various techniques have been proposed to improve the electrochemical reactivity and safety of the sulfur-carbon composite, which is a positive electrode active material.

[0009] In order to improve the performance of such a lithium-sulfur battery, it is necessary to maximize the reactivity of the positive electrode active material. Since sulfur used as the positive electrode active material of the lithium-sulfur battery has no conductivity, a carbon material is used as a carrier to maximize the reactivity, and a sulfur-carbon composite in which the carbon material and sulfur are mixed is mainly used.

[0010] However, when a carbon material having a high specific surface area and high porosity is used as a carrier for sulfur in this way, the particle size of the carbon material has a great influence on the discharge capacity and energy density of the lithium-sulfur battery. Therefore, it is essential to adjust the particle size of the carbon material and it is necessary to have a narrow particle size distribution.

[0011] Conventionally, a step of pulverizing the carbon material has been performed to adjust the particle size of the carbon material, and there is a problem that small particle sizes and large particle sizes coexist due to the pulverization and the particle size distribution is wide.

[0012] Therefore, research on a method for controlling the particle size of a porous carbon material having a narrow particle size distribution is required.

Summary of the Invention

Problems to be Solved by the Invention

[0013] The present invention has been made in view of the above problems, and by performing a continuous process, a method for controlling the particle size of a porous carbon material with high productivity, a narrow particle size distribution, and capable of producing a target particle size D 50 is provided.

Means for Solving the Problems

[0014] In order to achieve the above problems, According to one aspect of the present invention, there is provided a method for manufacturing a porous carbon material with controlled particle size of the following embodiments.

[0015] The method for manufacturing a porous carbon material with controlled particle size according to the first embodiment is as follows. (1) Crushing the porous carbon material using a centrifugal mill; (2) Sieving the crushed porous carbon material obtained in step (1) to obtain a porous carbon material with controlled particle size. The aperture of the sieve is 2.8 to 4 times the particle size D 50 of the porous carbon material with controlled particle size.

[0016] According to the second embodiment, in the first embodiment, Step (1) can be performed at an angular velocity of 30 to 125 Rad / s using the centrifugal mill.

[0017] According to the third embodiment, in the first or second embodiment, Step (2) can be performed with centrifugal force applied to the crushed porous carbon material.

[0018] According to the fourth embodiment, in any one of the first to third embodiments, After step (2), it may further include (3) collecting the porous carbon material that has passed through the sieve.

[0019] According to the fifth embodiment, in any one of the first to fourth embodiments, The centrifugal mill may include a plurality of rotating teeth.

[0020] According to the sixth embodiment, in any one of the first to fifth embodiments, Each of the plurality of rotating teeth has a triangular prism shape and may be arranged so as to face the rotation axis of the centrifugal mill.

[0021] According to the seventh embodiment, in any one of the first to sixth embodiments, the centrifugal grinder may include a cylindrical sieve arranged to surround the plurality of rotor teeth.

[0022] According to the eighth embodiment, in any one of the first to seventh embodiments, the shortest distance between the plurality of rotor teeth and the sieve may be 0.5 to 2 mm.

[0023] According to the ninth embodiment, in any one of the first to eighth embodiments, the porous carbon material may include one or more selected from the group consisting of carbon nanotubes, carbon black, carbon nanofibers, graphene, graphite, and activated carbon.

[0024] According to the tenth embodiment, in any one of the first to ninth embodiments, the porous carbon material with controlled particle size may have a BF (Broadness Factor) value of 7 or less according to the following formula 1.

[0025] <Formula 1> BF = (particle size D of the porous carbon material with controlled particle size 90 / particle size D of the porous carbon material with controlled particle size 10 ).

[0026] According to the eleventh embodiment, in any one of the first to tenth embodiments, the standard deviation of the particle size D 10 ~ D 50 of the porous carbon material with controlled particle size may be 1.5 μm or less.

[0027] According to the twelfth embodiment, in any one of the first to eleventh embodiments, the particle size D 50 of the porous carbon material with controlled particle size may be 100 μm or less.

[0028] According to the 13th embodiment, in any one of the 1st to 12th embodiments, The tap density of the porous carbon material before performing pulverization in the step (1) may be the same as or larger than the tap density of the porous carbon material with controlled particle size obtained in the step (2).

[0029] According to the 14th embodiment, in any one of the 1st to 13th embodiments, The step (1) and the step (2) may be performed simultaneously.

[0030] According to another aspect of the present invention, there are provided a porous carbon material, a sulfur-carbon composite, and a lithium-sulfur battery according to the following embodiments.

[0031] The porous material according to the 15th embodiment is manufactured by any one of the 1st to 14th embodiments and has an angular particle shape.

[0032] includes a porous carbon material manufactured by any one of the 1st to 14th embodiments and a sulfur-based material supported on at least a part of the surface of the porous carbon material.

[0033] The lithium-sulfur battery according to the 17th embodiment includes a positive electrode including the sulfur-carbon composite according to the 16th embodiment, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

Advantages of the Invention

[0034] The method for controlling the particle size of the porous carbon material of the present invention can manufacture a porous carbon material having a target particle size, can provide a porous carbon material having a narrow particle size distribution, and can continuously manufacture a porous carbon material with continuously controlled particle size by being performed in a continuous process, and has the effects of short process time, economic efficiency, and high productivity.

[0035] In addition, when sulfur S8 is supported as an active material of a lithium-sulfur battery using a porous carbon material with controlled particle size according to the present invention, it may have an advantage that the utilization rate of sulfur is increased and the electrochemical performance of the lithium-sulfur battery can be improved. However, the effects of the present invention are not limited thereto.

Brief Description of Drawings

[0036]

Figure 1

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Figure 6

Modes for Carrying Out the Invention

[0037] Hereinafter, the present invention will be described in more detail.

[0038] The terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. The inventors themselves must interpret them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that they can appropriately define the concept of the terms in order to explain the invention in the best way.

[0039] As used herein, the term "composite" means a substance in which two or more materials are combined to form physically and chemically different phases and exhibit a more effective function.

[0040] In the present invention, "particle size D 10 " means the size of particles at the 10% reference of the volume cumulative particle size distribution of the particles to be measured, and "particle size D 50 " means the size of particles at the 50% reference of the volume cumulative particle size distribution of the particles to be measured, and "particle size D 90 " means the size of particles at the 90% reference of the volume cumulative particle size distribution of the particles to be measured.

[0041] The particle sizes D 10 , D 50 and D 90 can each be measured using the laser diffraction method. For example, the particle powder to be measured is dispersed in a dispersion medium, introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000), irradiated with ultrasonic waves of about 28 kHz at an output of 60 W, and after obtaining a volume cumulative distribution graph, it can be measured by determining the particle sizes corresponding to 10%, 50%, and 90% of the volume cumulative distribution. That is, for example, the average particle size D 50 represents the median or median diameter in the particle size distribution graph and indicates the size of particles at the 50% point in the cumulative distribution. The particle size indicates the diameter of the particle, and the diameter of the particle indicates the longest length within the particle.

[0042] The term "porosity" used in this specification means the ratio of the volume occupied by pores to the total volume in a certain structure, and the unit "vol%" is used, and it can be used interchangeably with terms such as void fraction and porosity. The porosity can be measured by the method of ISO 15901:2019 known in the art.

[0043] A method for producing a porous carbon material according to one aspect of the present invention is (1) a step of pulverizing the porous carbon material using a centrifugal pulverizer, and (2) a step of sieving the pulverized porous carbon material obtained in the step (1) to obtain a porous carbon material with controlled particle size.

[0044] The mesh opening of the sieve is 2.8 to 4 times the particle size D of the porous carbon material with controlled particle size. 50 It is 2.8 to 4 times that of D.

[0045] In one embodiment of the present invention, the mesh opening of the sieve can be 2.8 to 4 times the target particle size D. 50 It can be 2.8 to 4 times that of D.

[0046] The step (1) is a step of pulverizing the porous carbon material using a centrifugal grinder. In this specification, pulverizing using a centrifugal grinder may also be referred to as "centrifugal pulverization".

[0047] The porous carbon material contains non-uniform pores inside the particles (closed pores) and / or on the surface of the particles (open pores). At this time, the average diameter of the pores is, for example, in the range of 1 to 200 nm, and the porosity can be 10 to 90 vol% of the total volume of the porous carbon material. The average diameter of the pores can be measured by a known method such as the BET measurement method using gas adsorption or mercury intrusion porosimetry.

[0048] The form of the porous carbon material is not particularly limited, such as spherical, rod-shaped, needle-shaped, plate-shaped, tubular or bulk form, etc.

[0049] The type of the porous carbon material is not particularly limited as long as it has a porous structure or a high specific surface area. For example, it contains one or more selected from the group consisting of carbon nanotubes, carbon black, carbon nanofibers, graphene, graphite and activated carbon, and preferably may contain carbon nanotubes. The porous carbon material produced by the method according to one aspect of the present invention controls the particle size of the starting porous carbon material and / or the uniformity of the particle size distribution, and does not change the type of the porous carbon material during the manufacturing process.

[0050] The carbon nanotubes may include, but are not limited to, one or more selected from the group consisting of single-walled carbon nanotubes and multi-walled carbon nanotubes. The manufacturing method according to one aspect of the present invention does not induce chemical deformation of the porous carbon material during the pulverization process and / or the sieving process. Specifically, when using multi-walled carbon nanotubes as the starting material in the manufacturing method, the porous carbon nanotubes are not chemically deformed into single-walled carbon nanotubes or the like.

[0051] The carbon black may include, but is not limited to, one or more selected from the group consisting of Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black.

[0052] The carbon nanofibers may include, but are not limited to, one or more selected from the group consisting of graphite nanofibers, carbon nanofibers, and activated carbon fibers.

[0053] The graphite may include, but is not limited to, one or more selected from the group consisting of natural graphite, artificial graphite, and expanded graphite.

[0054] Conventionally, a ball mill or a blade has been used to pulverize a porous carbon material in order to adjust the particle size of the porous carbon material. However, in the conventional pulverization method, there is a problem that the particle size distribution is wide because the porous carbon material randomly contacts the ball or the blade and porous carbon having a large particle size and a porous carbon material having a small particle size coexist.

[0055] Also, referring to FIGS. 1 and 2, in the case of the porous carbon material obtained by centrifugal pulverization and then sieved to control the particle size as in the present invention, when the particle size is controlled, it is sieved, so that further wear on the particle surface or further pulverization of the particle size can be prevented. On the other hand, after pulverization by a ball mill or the like, if not sieved, the particles charged into the ball mill or the like may continue to be pulverized, or the surface may be worn and a large amount of fine powder may be generated, resulting in a problem that the tap density becomes high.

[0056] The present invention can perform the step of sieving the centrifugally pulverized porous carbon material, which is step (2) described later, after pulverizing the porous carbon material using a centrifugal pulverizer. Therefore, in order for the centrifugally pulverized porous carbon material to pass through the sieve, most of the porous carbon material charged into the centrifugal pulverizer needs to be pulverized by contacting the rotating tooth of the centrifugal pulverizer. When the particle size becomes small enough to pass through the sieve by centrifugal pulverization, it passes through without being further pulverized. Thus, the rotating tooth of the centrifugal pulverizer and the porous carbon material contact each other a minimum number of times, thereby resulting in a very low fine powder generation rate and a narrow particle size distribution. In the present invention, the fine powder may mean that the particle size is 7 μm or less. At this time, the particle size of the fine powder is the particle size D 10 may mean.

[0057] Also, since the centrifugal pulverization pulverizes the porous carbon material so as to tear it, the shape of the centrifugally pulverized porous carbon material is not spherical, and the porous carbon material may have an angular particle shape. For example, the porous carbon material may have a particle shape having a prismoidal sphericity of a truncated pyramid.

[0058] Referring to FIG. 6, it is confirmed that the surface (left side) of the porous carbon material pulverized by a jet mill or the like is relatively flat, while the surface (right side) of the porous carbon material pulverized by a centrifugal pulverizer is relatively rough. It is confirmed that the porous carbon material on the right side has an angular particle shape due to its rough surface characteristics.

[0059] In an embodiment of the present invention, the step (1) may be performed by rotating at an angular velocity of 30 to 125 Rad / s using a centrifugal grinder for pulverization. Specifically, it may be rotated and pulverized at an angular velocity of 30 to 95 Rad / s. When the speed of centrifugal pulverization in the step (1) is the above-mentioned speed, it is advantageous in that while pulverizing the particle size of the porous carbon material to be small, it can be uniformly controlled and the tap density can be prevented from increasing.

[0060] In an embodiment of the present invention, the centrifugal grinder may include a plurality of rotor teeth, and may pulverize the porous carbon material while the rotor teeth rotate. Specifically, the centrifugal grinder may include, for example, 2 to 20, 4 to 18, 6 to 16, 8 to 14, 10 to 14, or 10 to 12 rotor teeth.

[0061] Also, in an embodiment of the present invention, each of the plurality of rotor teeth may have a triangular prism shape, and the plurality of rotor teeth may be arranged so as to face the rotation axis of the centrifugal grinder. Specifically, along the rotation axis of the centrifugal grinder, in a top view, it may be arranged such that the vertical cross-sections of the triangular prisms are in contact with each other at the center of the centrifugal grinder.

[0062] In an embodiment of the present invention, the plurality of rotor teeth may be made of, for example, stainless steel, titanium, or stainless steel material provided with a protective coating, but is not limited thereto.

[0063] In an embodiment of the present invention, in the step (1), a centrifugal grinder having rotor teeth may be used, and for example, a ZM200 device manufactured by Retsch may be used.

[0064] In an embodiment of the present invention, the centrifugal pulverization is performed at 6,000 to 23,000 rpm, and the particle size of the porous carbon material can be adjusted within this range. Specifically, the centrifugal pulverization may be performed at a speed of 6,000 to 23,000 rpm, specifically 6,000 to 18,000 rpm, using a ZM200 device manufactured by Retsch.

[0065] In one embodiment of the present invention, since the magnitude of the force applied can vary even at the same rpm depending on the size of the centrifugal grinder, the rpm can be adjusted to grind at an angular velocity of 30 to 125 Rad / s according to the following formula in consideration of the size of the centrifugal grinder.

[0066] Angular velocity = (RPM × Circumference) / 60 seconds In the above formula, "circumference" refers to the distance traveled during one rotation of one rotor tooth.

[0067] The step (2) is a step of sieving the porous carbon material centrifugally ground in the step (1).

[0068] In one embodiment of the present invention, the sieve may be provided in the centrifugal grinder and may be provided on the outer periphery of the centrifugal grinder. Specifically, the sieve may be provided so as to surround a plurality of rotor teeth in the centrifugal grinder.

[0069] In one embodiment of the present invention, the sieve is cylindrical and may be arranged so as to surround the plurality of rotor teeth. For example, in a top view of the centrifugal grinder, the shortest distance between the plurality of rotor teeth and the sieve may be 0.1 to 5 mm, 0.5 to 2 mm, or 0.7 mm to 1.2 mm, for example, 1 mm. The sieve may include a mesh having trapezoidal and / or circular holes.

[0070] In one embodiment of the present invention, when the rotor teeth rotate, the porous carbon material is ground, and the porous carbon material with the particle size controlled to the desired size passes immediately through a sieve located outside the peripheral portion where a series of rotor teeth are arranged while under centrifugal force, so that the particle size can be made smaller and / or the problem of surface damage can be solved. According to one aspect of the present invention, by performing the step (1) and the step (2) simultaneously, the particle size can be controlled to the desired size, and a porous carbon material having a narrow particle size distribution can be obtained.

[0071] Thus, in one embodiment of the present invention, it is desirable that the step (2) be performed with centrifugal force applied to the pulverized porous carbon material.

[0072] The step (2) may be a continuous process in which the porous carbon material centrifugally pulverized in step (1) moves to a sieve and is sieved, and steps (1) and (2) are performed simultaneously. That is, it is desirable that the step (2) not separately collect the porous carbon material centrifugally pulverized in the step (1) and put it into a sieve. Specifically, if the porous carbon material is centrifugally pulverized and has a particle size such that the centrifugally pulverized porous carbon material passes through a sieve, it can pass through the sieve and be sorted, and the centrifugal pulverization in step (1) and the sieving process in step (2) can be performed simultaneously. Since steps (1) and (2) are performed simultaneously, the process time is very short and the process efficiency is excellent.

[0073] The sieve used in the step (2) can control the particle size of the porous carbon material by adjusting the mesh opening. The mesh opening of the sieve is the particle size D 50 (target D 50 ) may be 2.8 to 4 times (2.8 ≤ mesh opening / target D 50 ≤ 4), and by limiting the range of the mesh opening of the sieve as described above, the target particle size D of the porous carbon material 50 can be obtained, and a porous carbon material with a narrow particle size distribution can be obtained.

[0074] In one embodiment of the present invention, the target particle size D of the porous carbon material 50 is, for example, the particle size D of the porous carbon material produced by one aspect of the present invention 50 and may be, for example, 10 μm to 100 μm, specifically 20 μm to 80 μm, 20 μm to 70 μm, or 20 μm to 66 μm.

[0075] Generally, when only the step of sieving the porous carbon material without performing centrifugal pulverization is performed, the particle size D of the sieved porous carbon material 50Becomes about 1 / 2 of the sieve opening, and the particle size D of the porous carbon material is less than 1 / 2 of the sieve opening 50 Is impossible to achieve. That is, the particle size D of the target porous carbon material 50 To obtain, the sieve opening must be at least about 2 times the particle size D of the target porous carbon material. If it is less than 2 times, the particle size D of the target porous carbon material 50 Cannot be obtained. 50

[0076] In the present invention, since the porous carbon material is centrifugally pulverized in the step (1) and the overall particle size of the porous carbon material becomes small, the minimum sieve opening is 2.8 times the particle size D of the target porous carbon material, and less than 2.8 times is impossible to achieve. Also, if it exceeds 4 times, the effect of controlling the particle size of the porous carbon material cannot be obtained. Further, the sieve opening may be 60 to 700 μm, preferably 70 to 500 μm, more preferably 70 to 200 μm. 50

[0077] In the step (2), the porous carbon material sieved has a ratio (Broadness Factor; BF) of D 10 To the particle size of D 90 Of the particle size distribution that can be 7 or less. For example, the particle size D of the porous carbon material sieved 90 Can be 1 to 7 with respect to the D 10 Particle size of the porous carbon material, specifically 1 to 6, or more than 1 and 6 times or less (1 <D 90 / D 10 ≦ 6). Specifically, the BF value can be 1 to 7, 1 to 6, 2 to 5, 3 to 5.5, 3.5 to 5.4 or 3.78 to 5.36.

[0078] <Formula 1> BF = (Particle size D of the porous carbon material with controlled particle size 90 / Particle size D of the porous carbon material with controlled particle size 10 )

[0079] ​​This may mean that the finally produced porous carbon material has a very narrow particle size distribution. If the particle size D 90 of the sieved porous carbon material 10 is less than 1 times, specifically 1 or less, with respect to the particle size D of the porous carbon material, it means that an excessive amount of fine powder with a small particle size was produced. If it exceeds 6 times, it means that an excessive amount of coarse powder with a large particle size was produced, and it may mean that the particle size distribution is very wide.

[0080] Also, the standard deviation of the particle size D 10 ~D 50 of the porous carbon material sieved in the step (2) can be 1.5 μm or less. That is, according to the method for controlling the particle size of the porous carbon material of the present invention, not only can the porous carbon material be obtained as the target particle size D 50 , but it can also have a very narrow particle size distribution.

[0081] In this specification, the standard deviation of the particle size of the above D 10 ~D 50 can indicate the standard deviation with respect to D 10 , D 20 , D 30 , D 40 and the particle size D 50 .

[0082] According to an embodiment of the present invention, the particle size D 50 of the sieved porous carbon material can be 100 μm or less, 90 μm or less, 80 μm or less, or 70 μm or less. In an embodiment of the present invention, the particle size D 50 of the sieved porous carbon material can be, for example, 10 μm or less, 15 μm or less, 18 μm or less, or 20 μm or less.

[0083] Also, the tap density ρ1 of the porous carbon material before performing centrifugal pulverization in the step (1) is the same as or greater than the tap density ρ2 of the porous carbon material sieved in the step (2), specifically, it can be 1 times or more (ρ1 / ρ2 ≧ 1). That is, the tap density of the porous carbon material does not increase in the steps (1) and (2), and from this, it can be understood that the method for controlling the particle size of the porous carbon material of the present invention is to control the particle size without applying pressure to the porous carbon material.

[0084] The tap density means the apparent density of the powder obtained by vibrating the container under certain conditions when charging the powder. In one embodiment of the present invention, the tap density can be measured after tapping the container containing the porous carbon material 1,000 times.

[0085] In one embodiment of the present invention, after the step (2), it may further include (3) a step of collecting the porous carbon material that has passed through the sieve.

[0086] Therefore, the method for controlling the particle size of the porous carbon material of the present invention adjusts the particle size D of the porous carbon material targeted for the mesh opening of the sieve 50 to 2.8 to 4 times, so that the target particle size D of the porous carbon material 50 can be obtained, and a porous carbon material with a very narrow particle size distribution can be obtained. Also, since it is a continuous process, the manufacturing time is very short, resulting in excellent process efficiency and productivity.

[0087] According to another aspect of the present invention, a porous carbon material whose particle size is controlled by the above method can be provided.

[0088] The porous carbon material produced by the above method is only controlled in particle size as described above and does not induce chemical deformation, so it contains a plurality of irregular pores on the surface and / or inside, and a sulfur-based material can be supported on the plurality of pores on the surface and / or inside.

[0089] In one embodiment of the present invention, the porous carbon material produced by the above method has an angular particle shape.

[0090] According to another aspect of the present invention, there can be provided a sulfur-carbon composite including the obtained porous carbon material and a sulfur-based material supported on at least a part of the surface of the porous carbon material.

[0091] In one embodiment of the present invention, the sulfur-based material can be supported on all or at least a part of the inner and outer surfaces of the pores of the porous carbon material.

[0092] In one embodiment of the present invention, the sulfur-based material can be used without particular limitation as long as it can provide sulfur (S8) as an active material of a lithium-sulfur battery. For example, the sulfur-based material includes one or more of sulfur (S8) and sulfur compounds.

[0093] In one embodiment of the present invention, the sulfur-based material is inorganic sulfur (S8), Li2S n (n≧1), a disulfide compound including one or more of 2,5-dimercapto-1,3,4-thiadiazole and 1,3,5-trithiocyanuic acid; an organic sulfur compound; and a carbon-sulfur polymer ((C2S x ) n , x = 2.5 to 50, n≧2); and can be one including one or more selected from the group consisting of.

[0094] In one embodiment of the present invention, in the sulfur-carbon composite, the sulfur-based material can be included by physical adsorption with the porous carbon material or by chemical bonds such as covalent bonds and van der Waals bonds between sulfur element S and carbon in the porous carbon material.

[0095] In one embodiment of the present invention, it is desirable that the content of the sulfur-based material is 60 wt% or more, or 70 wt% or more, based on 100 wt% of the sulfur-carbon composite. For example, in the sulfur-carbon composite, the content of the sulfur-based material is desirably 60 wt% - 99 wt%, 70 wt% - 99 wt%, 75 wt% - 90 wt%, 70 wt% - 85 wt%, 70 wt% - 80 wt%, or 70 wt% - 75 wt% based on 100 wt% of the sulfur-carbon composite.

[0096] In the sulfur-carbon composite according to the present invention, the sulfur-based material is located on at least one surface of the inner and outer surfaces of the pores of the carbon material. At this time, it may exist in a region of less than 100%, desirably 1% - 95%, more desirably 60% - 90% of the total inner and outer surfaces of the carbon material. When the sulfur is within the above range on the surface of the carbon material, the maximum effect can be achieved in terms of the electron transfer area and the wettability of the electrolyte. Specifically, since sulfur is thinly and uniformly impregnated on the surface of the carbon material in the above range region, the electron transfer contact area can be increased during the charge and discharge process. If the sulfur is located in the 100% region of the entire surface of the carbon material, the carbon material is completely covered with sulfur, the wettability of the electrolyte decreases, the contact with the conductive material contained in the electrode decreases, making it difficult for electrons to be transferred and unable to participate in the reaction.

[0097] The sulfur-carbon composite may be simply mixed and compounded with the sulfur and the carbon material, or may have a coating form or a supported form of a core-shell structure. The coating form of the core-shell structure is one in which either the sulfur material or the carbon material coats the other substance. For example, the surface of the carbon material may be surrounded by sulfur, or vice versa. The supported form may be a form in which the sulfur-based material is filled inside the carbon material, particularly inside the internal pores. The form of the sulfur-carbon composite can be used in any form as long as it satisfies the content ratio of the sulfur and the carbon material presented above, and is not limited in the present invention.

[0098] In one embodiment of the present invention, the sulfur-carbon composite can be used as a cathode active material and / or a cathode additive of a lithium-sulfur battery, but the use of the present invention is not limited thereto.

[0099] According to another aspect of the present invention, a lithium-sulfur battery including a cathode including the aforementioned sulfur-carbon composite, an anode, a separator interposed between the cathode and the anode, and an electrolyte can be provided.

[0100] At this time, the configurations of the cathode, anode, separator, and electrolyte can be used without particular limitation as long as they are those used in lithium-sulfur batteries, and are not particularly limited in the present invention.

[0101] According to one embodiment of the present invention, the cathode includes the aforementioned sulfur-carbon composite, so that the sulfur loading rate is high, and thus it can show the advantage of improving the electrochemical performance. However, the effects of the present invention are not limited thereto.

[0102] Hereinafter, desirable examples are presented to assist in understanding the present invention. However, it is obvious to those skilled in the art that the following examples only illustrate the present invention, and various modifications and corrections are possible within the scope of the present invention and the scope of the technical idea. Of course, such modifications and corrections are included in the appended claims.

[0103] <Manufacture of Porous Carbon Material> Comparative Example 1 Carbon nanotubes (MWCNT) that were not centrifugally milled were used, and the particle size control process was not carried out.

[0104] Comparative Example 2 The carbon nanotubes (MWCNT) prepared in Comparative Example 1 were milled by a jet mill.

[0105] Examples 1 to 5 and Comparative Example 3 Carbon nanotubes (MWCNT) were put into a centrifugal grinder (Retsch, ZM200) equipped with a sieve, and while the carbon nanotubes were being ground, the particle size was controlled so that the ground carbon nanotubes were sieved while centrifugal force was applied. The target D 50 of the particle size of the carbon nanotubes (target D 50 ) was obtained by adjusting the mesh size, rpm, and angular velocity of the sieve, and the conditions are shown in Table 1 below.

[0106] Comparative Example 4 The carbon nanotubes (MWCNT) were sieved to control the particle size. The target D 50 of the particle size of the carbon nanotubes (target D 50 ) was obtained by adjusting the mesh size of the sieve, and the conditions are shown in Table 1 below.

[0107] Comparative Example 5 Carbon nanotubes (MWCNT) were obtained in the same manner as in Example 1, except that the particle size was controlled by putting them into a centrifugal grinder (Netzsch, CSM80) not equipped with a sieve.

[0108]

Table 1

[0109] Experimental Example 1. Measurement of the particle size of carbon nanotubes with controlled particle size The particle sizes of the centrifugally ground carbon nanotubes of Examples 1 to 5 and Comparative Examples 3 and 5, the carbon nanotubes of Comparative Example 1, the carbon nanotubes ground by a jet mill of Comparative Example 2, and the carbon nanotubes sieved in Comparative Example 4 were measured using a dry particle size measuring device (Microtrac), and the results are shown in Tables 2 and 3 and Figure 4 below.

[0110] On the other hand, by using different centrifugal grinders, the size of the centrifugal grinder changes, and the magnitude of the applied force changes. Therefore, in order to apply the same level of force (maintaining the angular velocity), the larger the size of the centrifugal grinder, the smaller the rpm number was adjusted.

[0111]

Table 2

[0112]

Table 3

[0113] From the results in Table 2 and Table 3 above, for the carbon nanotubes with the sieve aperture set to 2.8 to 4 times the particle size D of the target carbon nanotubes, 50 particle sizes identical or similar to the target D 50 were obtained. Also, the particle size D 90 of the carbon nanotubes showed results of more than 1 to 6 times that of D 10 , and the standard deviation of D 10 to D 50 of the carbon nanotubes showed results of 1.5 μm or less.

[0114] From this result, according to the method for controlling the particle size of the porous carbon material of the present invention, the target particle size D 50 of the porous carbon material can be obtained, and since it has a very narrow particle size distribution, it can be seen that the particle size is uniformly controlled.

[0115] On the other hand, for the carbon nanotubes in Comparative Example 1 where no grinding was performed, the particle size D 90 was 9.64 times that of D 10 , showing a very high result. Also, the standard deviation of D 10 to D 50 of the carbon nanotubes was also 10 μm, showing a very high result. Therefore, it was confirmed that the particle size control of the carbon nanotubes was not properly carried out, and carbon nanotubes with a very non-uniform particle size were produced.

[0116] In Comparative Example 2, jet mill pulverization was performed instead of centrifugal pulverization, and the standard deviation of D 10 ~D 50 of the carbon nanotubes was 0.72 μm, showing a low result. However, since the pulverization was not performed uniformly, the particle size D 90 of the carbon nanotubes was 10.37 times that of D 10 . That is, D 10 ~D 50 showed a relatively narrow particle size distribution, but since D 90 was present in a much larger amount than D 10 , it can be seen that the overall particle size distribution was wide and the carbon nanotubes were not uniformly pulverized.

[0117] On the other hand, in Comparative Example 3, the carbon nanotubes were centrifugally pulverized and sieved to control the particle size of the carbon nanotubes. The aperture of the sieve was 6.94 times the target particle size D 50 of the carbon nanotubes. As a result, the target particle size D 50 was obtained, but the particle size D 90 of the carbon nanotubes was 9.3 times that of D 10 , and the standard deviation of D 10 ~D 50 of the carbon nanotubes was 3.6 μm. It can be seen that the carbon nanotubes in Comparative Example 3 had a wide particle size distribution and non-uniform particle sizes. From this, it can be confirmed that if the aperture of the sieve is 2.8 to 4 times the target particle size D 50 of the carbon nanotubes, not only can the target particle size D 50 of the carbon nanotubes be obtained, but also a very narrow particle size distribution can be obtained and the particle sizes can be uniformly controlled.

[0118] In addition, in Comparative Example 4, the carbon nanotubes were not centrifugally pulverized, and only the sieving process was performed. Generally, when only the sieving process is performed, D 50 of the sieved carbon nanotubes is about 1 / 2 of the aperture of the sieve. In Comparative Example 4, the aperture of the sieve was the target particle size D50 is 2.14 times that of, the particle size D of the target carbon nanotubes 50 was obtained. However, since centrifugal grinding was not performed, the particle size D 90 is 6.5 times that of D 10 , and the standard deviation of D 10 ~D 50 is 1.57 μm, and it was found that the carbon nanotubes of Comparative Example 4 had a wide particle size distribution and non-uniform particle sizes, showing a low yield.

[0119] Also, Comparative Example 5 shows the D of the carbon material obtained when only centrifugal grinding was performed without sieving 10 ~D 50 has a large standard deviation, and since D 10 the particle size D with respect to the particle size 90 is large, it can be seen that the particle size deviation is large.

[0120] Therefore, when centrifugal grinding and sieving are simultaneously performed on the porous carbon material, and at this time, the mesh opening of the sieve is set to 2.8 to 4 times the particle size D of the target porous carbon material 50 it can be seen that a porous carbon material with a narrow particle size distribution can be obtained.

[0121] Experimental Example 2. Comparative evaluation of the tap density before and after particle size control A plurality of aggregates formed by entanglement of multi-walled carbon nanotubes (Cnano, MWCNT, tap density 0.14 g / cm 3 , uniformity of particle shape 1.52) were prepared. Then, the aggregates were ground at 18,000 rpm using a grinder (Retsch, ZM-200), and then sieved through a sieve with a mesh opening of 80 μm to prepare a porous carbon material with a modified particle shape.

[0122] The modified porous carbon material had a tap density of 0.07 g / cm when tapped 1,000 times 3It was measured as such, and the uniformity of the particle shape was measured to be 1.07. At this time, the tap density was measured using TAP-2S (manufactured by LOGAN) in accordance with ASTM B527-06. The uniformity of the particle shape indicates the ratio of the diameter of the circumscribed circle to the diameter of the inscribed circle of the particle, and was calculated as the average value of the ratio values of the diameter of the circumscribed circle / diameter of the inscribed circle of five arbitrarily selected particles.

[0123] From this, it was confirmed that the porous carbon material produced by the method for producing a porous carbon material according to an embodiment of the present invention can uniformly modify the particle shape without increasing the tap density before and after particle size control.

[0124] Experimental Example 3. Comparative evaluation of surface characteristics by particle size control method The SEM images of the porous carbon material produced in Comparative Example 2 and the porous carbon material produced in Example 1 are shown in FIG. 6.

[0125] The SEM image on the left shows the porous carbon material of Comparative Example 2, and the SEM image on the right shows the porous carbon material of Example 1.

[0126] Referring to FIG. 6, it was confirmed that the surface of the porous carbon material pulverized by a jet mill is relatively flat, while the porous carbon material pulverized by a centrifugal mill has a relatively rough surface and an angular particle shape.

[0127] From this, it can be seen that the surface characteristics of the porous carbon material with controlled particle size according to one aspect of the present invention have the characteristics of a low tap density and excellent particle shape uniformity.

Claims

1. (1) a step of pulverizing a porous carbon material using a centrifugal pulverizer; (2) a step of sieving the pulverized porous carbon material obtained in the step (1) to obtain a porous carbon material with a controlled particle size, The aperture of the sieve is 2.8 to 4 times the particle size D of the porous carbon material with the controlled particle size. ５０ A method for producing a porous carbon material.

2. The method for producing a porous carbon material according to claim 1, wherein the step (1) is performed at an angular velocity of 30 to 125 Rad / s using the centrifugal pulverizer.

3. The method for producing a porous carbon material according to claim 1, wherein the step (2) is performed with a centrifugal force applied to the pulverized porous carbon material.

4. The method for producing a porous carbon material according to claim 1, further comprising, after the step (2), (3) a step of collecting the porous carbon material that has passed through the sieve.

5. The method for producing a porous carbon material according to claim 1, wherein the centrifugal pulverizer includes a plurality of rotor teeth.

6. The method for producing a porous carbon material according to claim 5, wherein each of the plurality of rotor teeth has a triangular prism shape and is arranged so as to face the rotation axis of the centrifugal pulverizer.

7. The method for producing a porous carbon material according to claim 5, wherein the centrifugal pulverizer includes a cylindrical sieve disposed so as to surround the plurality of rotor teeth.

8. The method for producing a porous carbon material according to claim 7, wherein the shortest distance between the plurality of rotor teeth and the sieve is 0.5 to 2 mm.

9. The method for producing a porous carbon material according to claim 1, wherein the porous carbon material includes one or more selected from the group consisting of carbon nanotubes, carbon black, carbon nanofibers, graphene, graphite, and activated carbon.

10. The method for producing a porous carbon material according to claim 1, wherein the porous carbon material with a controlled particle size has a BF (Broadness Factor) value of 7 or less according to the following formula 1: <Formula 1> BF = (particle diameter D of the porous carbon material with controlled particle diameter ９０ / particle diameter D of the porous carbon material with controlled particle diameter １０ ).

11. The particle size D of the porous carbon material with controlled particle size １０ to D ５０ The manufacturing method of the porous carbon material according to any one of claims 1 to 10, wherein the standard deviation is 1.5 μm or less.

12. The particle size D of the porous carbon material with controlled particle size ５０ is 100 μm or less. The method for producing a porous carbon material according to claim 1.

13. The method for producing a porous carbon material according to claim 1, wherein the tap density of the porous carbon material before pulverization in the step (1) is the same as or greater than the tap density of the porous carbon material with a controlled particle size obtained in the step (2).

14. The method for producing a porous carbon material according to claim 1, wherein the step (1) and the step (2) are performed simultaneously.

15. A porous carbon material produced by the production method according to any one of claims 1 to 14 and having an angular particle shape.

16. A porous carbon material produced by the production method according to any one of claims 1 to 14, and A sulfur-carbon composite comprising a sulfur-based material supported on at least a part of the surface of the porous carbon material.

17. A lithium-sulfur battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, the positive electrode and the negative electrode each containing the sulfur-carbon composite according to claim 16.

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