KR102500254B1 - Composition of cathode materials for lithium-sulfur battery comprising mesoporous carbon-carbon wire structure and sulfur, producing method thereof and lithium-sulfur battery using it - Google Patents

Abstract

The present invention is a mesoporous carbon-carbon wire having a particle size of 80 to 800 nm, including a carbon structure containing mesopores having an average pore size of 3 to 5 nm and a carbon wire grown from the carbon structure including the mesopores. structure; It relates to a cathode material composition for a lithium-sulfur battery comprising sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure, a manufacturing method thereof, and a lithium-sulfur battery using the same. The cathode material composition for a lithium-sulfur battery of the present invention includes a spherical carbon nanostructure capable of preventing the elution of lithium polysulfide due to a high porosity and a high specific surface area with mesopores of various sizes, and mesoporous carbon particles. A mesoporous carbon-carbon wire structure composed of a carbon wire structure with high electrical conductivity capable of growing from a carbon wire structure with high electrical conductivity capable of interconnecting and supporting carbon particles and improving ion transport characteristics and electron transport characteristics is used, and the mesopores It contains a large amount of sulfur impregnated into the pores, which are empty spaces inside the carbon-carbon wire structure. If this is used as a cathode material, it can support a high content of sulfur in the cathode, so a lithium-sulfur battery with high energy density can be obtained. there is.

Description

Composition of cathode materials for lithium-sulfur battery comprising mesoporous carbon-carbon wire structure and sulfur, producing method thereof and lithium-sulfur battery using it}

The present invention relates to a cathode material composition for a lithium-sulfur battery comprising a mesoporous carbon-carbon wire structure and sulfur, and more particularly, to a mesoporous carbon-carbon wire structure prepared using mesoporous carbon impregnated with sulfur It relates to a cathode material composition for a lithium-sulfur battery, a method for preparing the same, and a lithium-sulfur battery using the same as a cathode material.

As the environment and energy resource depletion problems and the need for high energy and high efficiency of energy storage devices emerge, it is necessary to develop next-generation secondary battery technology that has higher energy density than current lithium secondary batteries, secures stability, and has excellent lifespan characteristics. .

Among several candidates for next-generation secondary batteries, sulfur batteries are systems that use low-cost sulfur as the main active material and can solve the problem of by-products from the petrochemical industry without the problem of resource limitations. Therefore, a very high energy density of 2,600 Wh/kg, which is about 7 times higher than that of a conventional lithium secondary battery (370 Wh/kg), is theoretically possible.

Recently, the energy density of electric vehicles and small-sized lithium ion batteries has rapidly improved and is approaching the theoretical limit energy density at the level of 300Wh/kg. Companies around the world are fiercely competing to develop next-generation batteries with high energy density of 350Wh/kg or more. In this situation, it is very urgent to secure technology for a sulfur battery system capable of realizing high energy density.

Despite many advantages, sulfur batteries are still difficult to commercialize, because it is difficult to implement a theoretically high energy density with current technology, and capacity degradation occurs rapidly as the lifespan progresses.

The reason why it is difficult to realize high energy density of a sulfur battery is that LiS or Li ₂ S, which is a reaction product of sulfur and lithium used as a cathode material, is an insulator with a very low conductivity of 5 × 10 ^-30 S / cm. This is because a large amount of conductive material is required to form a conductive path, and the amount of conductive agent and binder used is increased to use a large amount of sulfur, so there is a limit to increasing the energy density of the sulfur anode. am.

In addition, the reason why it is difficult to extend the lifespan of a sulfur battery is that polysulfide (PS) is eluted from the anode to the electrolyte during charging and discharging. When PS is eluted from a Li-S battery by PS elution, active material loss and capacity degradation occur due to continuous PS elution occurring at the anode, and self-discharge occurs due to the shuttle reaction of PS eluted in the electrolyte. occurs, and the eluted PS blocks the pores of the separator or forms a non-conductive Li ₂ S film on the surface of the Li metal cathode, thereby increasing the resistance of the entire system and degrading the lifespan.

In order to control the elution of lithium polysulfide, an intermediate product generated during the charging and discharging reaction of a sulfur battery, into the electrolyte, the most promising method is to use conductive porous carbon with sufficient internal space to support sulfur. .

The requirements for the sulfur-supporting material include high porosity capable of supporting sulfur, high electrical conductivity enabling the movement of electrons generated by the electrochemical reaction of sulfur, and suppression of volume expansion due to the electrochemical reaction of sulfur. mechanical strength, distribution of pores of various sizes and high specific surface area that can prevent the elution of lithium polysulfide, an intermediate product. Therefore, these requirements The development of a carbon structure that can satisfy the demand is required.

In order to obtain a carbon-sulfur-polymer composite for high energy density sulfur batteries having a sulfur content of 70% or more in the cathode and a sulfur utilization rate of 1000 mAh/g or more, the movement of polysulfide in the cathode to the cathode is suppressed to reduce capacity loss and increase in resistance. It is necessary to develop a multifunctional separator coating technology that can provide protection for the stability of the cathode interface. It is essential to reduce the content of the electrolyte compared to sulfur, which is a reactant. To this end, it is necessary to devise and mass-produce an electrolyte system so that all components of the electrolyte can increase the solubility of polysulfide.

In addition, a sulfur-carbon-polymer composite that can increase the utilization rate of sulfur by suppressing the elution and diffusion of lithium polysulfide and increasing the electrical conductivity in the electrode by introducing a polymer with low density and excellent electrical conductivity to the sulfur-carbon structure impregnated with elemental sulfur. development is required.

Korean Patent Publication No. 10-2004-0037322 Korean Patent Publication No. 10-2021-0021655 Korean Patent Publication No. 10-2014-0122886 Korean Patent Publication No. 10-2019-0066839

In order to solve the above problems, the present invention is a mesoporous carbon produced by combining a carbon wire, which is easy to transfer electrons and can be produced relatively economically compared to carbon nanotubes, to a mesoporous carbon structure manufactured using a porous silica structure. -Anode for lithium-sulfur battery having high energy density as it can be manufactured at a relatively low cost and can support a high content of sulfur while compensating for the disadvantages of each of the conventional carbon particles and carbon wire by impregnating a large amount of sulfur into the carbon wire structure It is an object to provide a re-composition.

In order to achieve the above object, the present invention comprises the steps of preparing a porous silica structure; preparing a porous silica-carbon structure by coating a surface of the porous silica structure with a carbon-containing polymer material and heat-treating; preparing a porous silica-carbon-carbon wire structure by growing a carbon wire on the porous silica-carbon structure; preparing a mesoporous carbon-carbon wire structure by removing silica from the porous silica-carbon-carbon wire structure; and impregnating the mesoporous carbon-carbon wire structure with sulfur.

In the above manufacturing method, the porous silica structure is TEOS (Tetraethyl orthosilicate) 2 to 10% by weight, 20 to 35% by weight of ammonia water 2 to 15% by weight, distilled water 3 to 25% by weight, TEOS volume based on the total weight of the composition 0.14 to 0.5 times the volume of organosilane, and the remainder is preferably prepared using a composition containing a solvent selected from ethanol and methanol.

In the above manufacturing method, the porous silica structure is synthesized by mixing 20 to 35% by weight of ammonia water, distilled water, organosilane and TEOS in a solvent and stirring for 5 hours or more; removing the liquid phase, separating only the solid content, and drying at 90 to 110° C. for 12 hours or more; And it is preferably prepared by a method comprising the step of heat treatment at 500 ~ 600 ℃ for 4 ~ 6 hours.

In the above production method, the porous silica structure is preferably spherical with a particle size of 80 to 700 nm.

In the manufacturing method, the carbon-containing polymer is a thermoplastic resin selected from phenol resin, polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), and polystyrene (PS). , preferably a mixture of cellulose.

In the manufacturing method, the thermoplastic resin and cellulose are preferably mixed in a weight ratio of 6:4 to 8:2.

In the above manufacturing method, the porous silica-carbon structure is prepared by dissolving a carbon-containing polymer of 0.2 to 0.5 times the weight of the porous silica structure in distilled water 2.5 to 3.5 times the weight of the porous silica structure; coating the porous silica structure with the carbon-containing polymer material by dissolving the carbon-containing polymer material and then introducing the porous silica structure and leaving it for at least 1 hour; evaporating and drying the porous silica structure coated with the carbon-containing polymer at 100 to 120° C. for 12 hours or more; Oxidizing the dried structure for 1 to 5 hours after heating the dried structure to 180 to 220 ° C at a heating rate of 1 ° C / min in an air atmosphere; raising the temperature of the oxidized structure to 800 to 1,000° C. at a heating rate of 5° C./min, followed by heat treatment for 5 to 25 hours to carbonize the carbon-containing polymer; And it is preferably prepared by a method comprising the step of naturally cooling to room temperature.

In the above manufacturing method, after the step of coating the porous silica structure with a carbon-containing polymer material, a step of aging at 75 to 85 ° C. for 3 hours or more may be further included.

In the manufacturing method, the porous silica-carbon-carbon wire structure comprises: mixing 4 to 5% by weight of magnesium (Mg) powder relative to the weight of the porous silica-carbon structure; heat-treating a powder in which magnesium is mixed in a porous silica-carbon structure at 600 to 700° C. for 5 to 7 hours in a nitrogen atmosphere; and pulverizing the heat-treated sample and passing through a 150 to 250 mesh sieve to obtain a porous silica-carbon-carbon wire structure.

In the above manufacturing method, the mesoporous carbon-carbon wire structure is obtained by putting 8 to 12 times the weight of distilled water of the solid content of the porous silica-carbon-carbon wire structure in a reaction container and slowly injecting hydrofluoric acid into the distilled water to obtain 15 to 25% by weight. Preparing a hydrofluoric acid solution of; Dissolving the silica material in the porous silica-carbon-carbon wire structure by slowly injecting the porous silica-carbon-carbon wire structure into the hydrofluoric acid solution, sealing it, and reacting for 12 hours or more; filtering to remove the solution and washing the solid content with distilled water 3 to 5 times; And it is preferably prepared by a method comprising the step of drying the separated solid content at 90 ~ 110 ℃ for 10 ~ 14 hours.

In the above production method, pulverizing elemental sulfur; mixing and pulverizing the pulverized sulfur and the mesoporous carbon-carbon wire structure in a weight ratio of 2 to 4:1; and heat treatment at 150 to 160° C. for 10 to 14 hours. Preferably, the mesoporous carbon-carbon wire structure is impregnated with sulfur.

In the manufacturing method, the mesoporous carbon-carbon wire structure preferably includes mesopores having an average pore size of 3 to 5 nm and a particle size of 80 to 800 nm.

In addition, the present invention includes a carbon structure containing mesopores having an average pore size of 3 to 5 nm, and a carbon wire grown from the carbon structure including the mesopores, and a mesopore carbon-carbon having a particle size of 80 to 800 nm. a wire structure; It provides a cathode material composition for a lithium-sulfur battery comprising sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure.

The lithium-sulfur battery cathode material composition is preferably prepared by the method of any one of claims 1 to 11.

In addition, the present invention includes a carbon structure containing mesopores having an average pore size of 3 to 5 nm, and a carbon wire grown from the carbon structure including the mesopores, and a mesopore carbon-carbon having a particle size of 80 to 800 nm. a wire structure; Provided is a lithium-sulfur battery comprising a cathode material composition for a lithium-sulfur battery including sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure as a cathode material.

In the lithium-sulfur battery, the lithium-sulfur battery cathode material composition is preferably prepared by the method of any one of claims 1 to 11.

The cathode material composition for a lithium-sulfur battery of the present invention includes a spherical carbon nanostructure capable of preventing dissolution of lithium polysulfide due to mesopores developed and having pores of various sizes, high porosity and high specific surface area, and mesoporous carbon A mesoporous carbon-carbon wire structure composed of a carbon wire structure with high electrical conductivity capable of growing from particles to interconnect and support the carbon particles and at the same time improving ion transport characteristics and electron transport characteristics is used, It contains a large amount of sulfur impregnated into the pores, which are empty spaces inside the empty carbon-carbon wire structure. If this is used as a cathode material, a lithium-sulfur battery with high energy density can be obtained because it can support a high content of sulfur in the cathode. can

1 is a SEM image of a porous silica structure.
2 is a SEM image of a porous silica-carbon structure.
3 is a SEM image of a mesoporous carbon structure.
4 is a SEM image of a mesoporous carbon-carbon wire structure.
5 is a SEM image confirming the silica core size of the porous silica structure according to the reaction time. The reaction times are (A) 1 hour, (B) 2 hours and (C) 5 hours.
6 is a SEM image confirming the silica core size of the porous silica structure according to the amount of the reaction catalyst. The amount of the reaction catalyst is (A) 2% by weight, (B) 5% by weight, (C) 9% by weight and (D) 15% by weight.
7 is an SEM image confirming the silica core size of the porous silica structure according to the amount of distilled water. The amount of distilled water is (A) 3% by weight, (B) 7% by weight, (C) 11% by weight, (D) 15% by weight and (E) 23% by weight.
8 is a SEM image confirming the silica core size of the porous silica structure according to the amount of TEOS. The amount of TEOS is (A) 2% by weight, (B) 6% by weight and (C) 10% by weight.
Figure 9 shows the results of confirming the change in the size of the silica core of the porous silica structure according to the reaction conditions.
10 shows nitrogen isotherms and pore distributions of porous silica structures according to silica core sizes.
Figure 11 shows the results of confirming the physical properties of the porous silica structure according to the size of the silica core.
12 is a SEM image of the result of confirming the core-shell structure of the porous silica structure according to the type of surfactant.
Figure 13 shows the nitrogen isotherm of the core-shell of the porous silica structure according to the type of surfactant.
14 shows the pore distribution of the core-shell of the porous silica structure according to the type of surfactant.
15 is a SEM image confirming the core-shell structure of the porous silica structure according to the ratio of organosilane.
16 shows the core-shell nitrogen isotherm and pore distribution of the porous silica structure according to the ratio of organosilane.
17 is an SEM image of the mesoporous carbon structure according to the organosilane ratio. The organosilane/TEOS volume ratio is (A) 0.125, (B) 0.375, and (C) 1.
18 is a nitrogen isotherm of a mesoporous carbon structure according to an organosilane ratio.
19 is a pore distribution curve of the mesoporous carbon structure according to the organosilane ratio.
20 is a result of confirming the physical properties of the mesoporous carbon structure according to the organosilane ratio.
21 is a nitrogen isotherm of a mesoporous carbon structure according to a carbon-containing-polymer ratio.
22 is a pore distribution curve of the mesoporous carbon structure according to the ratio of carbon-containing polymers.
23 compares the physical properties of mesoporous carbon structures according to the ratio of carbon-containing polymers.
24 is an SEM image confirming the structure of the mesoporous carbon structure according to the particle size. The particle sizes are (A) 80 nm, (B) 300 nm and (C) 500 nm.
25 is a result of confirming the nitrogen isotherm, pore distribution, and physical properties of the mesoporous carbon structure according to the particle size.
26 is a SEM image confirming the structure of the mesoporous carbon structure according to the heat treatment temperature. (A) shows the case where the organosilane/TEOS volume ratio is 0.125, (B) is 0.375, and (C) is 1.
27 is a result of confirming the nitrogen isotherm, pore distribution, and physical properties of the mesoporous carbon structure according to the heat treatment temperature.
28 is a result of confirming the nitrogen isotherm, pore distribution, and physical properties of the mesoporous carbon structure according to the heat treatment time.
29 is a result of confirming the particle size distribution of the mesoporous carbon structure according to the heat treatment time.
30 shows nitrogen isotherms and pore distribution curves of Example 1.
31 shows nitrogen isotherms and pore distribution curves of the heat-treated mesoporous carbon structure of Comparative Example 1 before sulfur impregnation.
32 shows nitrogen isotherms and pore distribution curves of the heat-treated mesoporous carbon structure of Comparative Example 2 before sulfur impregnation.
33 shows nitrogen isotherms and pore distribution curves of the heat-treated mesoporous carbon structure of Comparative Example 3 before sulfur impregnation.
34 is a SEM image confirming the structure of the mesoporous carbon-carbon wire structure of Example 1.
35 is a SEM image confirming the structure of the heat-treated mesoporous carbon structure of Comparative Example 1 before sulfur impregnation.
36 is an SEM image confirming the structure of the heat-treated mesoporous carbon structure of Comparative Example 2 before sulfur impregnation.
37 is a SEM image confirming the structure of the heat-treated mesoporous carbon structure of Comparative Example 3 before sulfur impregnation.
38 is a thermogravimetric analysis (TGA) result of the sulfur-carbon composites of Example 4 and Comparative Examples 1 to 3.
39 is an XRD analysis result of the sulfur-carbon composites of Example 4 and Comparative Examples 1 to 3.
40 is a battery performance evaluation graph for analyzing the lithium ion charge and discharge performance of Example 4 and Comparative Examples 1 to 3.
FIG. 41 shows the discharge performance for each cycle compared to the discharge performance of the initial one cycle according to the number of charge/discharge cycles from the battery performance evaluation graph of FIG. 40 .

The present invention comprises the steps of preparing a porous silica structure; preparing a porous silica-carbon structure by coating a surface of the porous silica structure with a carbon-containing polymer material and heat-treating; preparing a porous silica-carbon-carbon wire structure by growing a carbon wire on the porous silica-carbon structure; preparing a mesoporous carbon-carbon wire structure by removing silica from the porous silica-carbon-carbon wire structure; and impregnating the mesoporous carbon-carbon wire structure with sulfur.

In addition, the present invention includes a carbon structure containing mesopores having an average pore size of 3 to 5 nm, and a carbon wire grown from the carbon structure including the mesopores, and a mesopore carbon-carbon having a particle size of 80 to 800 nm. a wire structure; It relates to a cathode material composition for a lithium-sulfur battery comprising sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure.

In addition, the present invention includes a carbon structure containing mesopores having an average pore size of 3 to 5 nm, and a carbon wire grown from the carbon structure including the mesopores, and a mesopore carbon-carbon having a particle size of 80 to 800 nm. a wire structure; It relates to a lithium-sulfur battery characterized in that a cathode material composition for a lithium-sulfur battery including sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure is used as a cathode material.

Hereinafter, the present invention will be described in detail.

1. Preparation of porous silica structure

The porous silica structure is prepared by a sol-gel reaction using a composition in which a silica (SiO ₂ ) raw material, a solvent, a catalyst, distilled water for hydrolysis, and a surfactant are mixed.

As a silica raw material, TEOS (Tetraethyl orthosilicate) is used. TEOS is preferably used in an amount of 2 to 10% by weight based on the total weight of the composition.

Ethanol or methanol is used as a solvent providing a space for silica synthesis.

Ammonia water, hydrochloric acid, nitric acid or sulfuric acid is used as a catalyst for silica synthesis. It is more preferable to use aqueous ammonia. As the ammonia water, it is preferable to use ammonia water with a concentration of 20 to 35% by weight, more preferably to use ammonia water with a concentration of 25 to 30% by weight, and particularly preferably to use ammonia water with a concentration of 28% by weight.

Distilled water is used for the hydrolysis reaction. Distilled water is preferably used in an amount of 3 to 25% by weight based on the total weight of the composition.

Surfactant is used for pore expansion. As the surfactant, organosilane {C ₁₈ -TMS (Trimethoxy(octadecyl)silane}, CTAB (Cetyltrimethylammoniumbromide), CTAC (Cetyltrimethylammoniumchloride), Divinylbenzene, Cellulose, Phenol resin, Polyvinyl Alcohol (Polyvinylalcohol) can be used, etc. It is particularly preferable to use organosilane, and the volume ratio of organosilane/TEOS is preferably used in an amount of 0.14 to 0.5, and an amount of 0.3 to 0.4 is used. It is more preferable to use, and it is particularly preferable to use an amount that becomes 0.375.

A porous silica structure is synthesized by mixing ammonia water, organosilane, and TEOS with ethanol or methanol as a solvent and reacting with stirring for 5 hours or more. It is more preferable to react for 5 to 7 hours to synthesize, and it is particularly preferable to react for 5 hours.

The synthesized silica structure is dried at 90 ~ 110 ℃ for 12 hours or more by removing the liquid phase and separating only the solid content. It is more preferable to dry at 100°C for 12 to 14 hours. It is preferable to remove the liquid phase using a centrifugal separator.

The dried silica structure is heat-treated at 500 to 600° C. for 4 to 6 hours to remove organic substances present therein to obtain a porous silica structure.

The porous silica structure is a spherical material with a particle size (diameter) of 80 to 700 nm and is used as a template for manufacturing mesoporous carbon-carbon wire negative electrode materials. The particle size of the porous silica structure is preferably 80 to 100 nm, and particularly preferably 80 nm, because pores formed between small particles affect physical properties.

2. Preparation of porous silica-carbon structure

A porous silica-carbon structure is prepared by coating the porous silica structure with a carbon-containing polymer material and heat-treating.

The carbon-containing polymer material to be coated on the silica surface is a thermoplastic resin selected from phenol resin, PVA (polyvinyl alcohol), PAN (polyacrylonitrile), PE (polyethylene), PP (polypropylene), PVC (polyvinylchloride) and PS (polystyrene) , mixed with cellulose. It is more preferable to use a mixture of a phenol resin and cellulose.

The thermoplastic resin and cellulose are preferably mixed in a weight ratio of 6:4 to 8:2, and more preferably mixed in a weight ratio of 7:3.

In distilled water 2.5 to 3.5 times the weight of the porous silica structure, 0.2 to 0.5 times the weight of the porous silica structure is dissolved in the carbon-containing polymer material. It is more preferable to use 0.2 to 0.3 times the weight of the porous silica structure of the carbon-containing polymer material, and it is particularly preferable to use 0.23 times the weight of the carbon-containing polymer material.

After the carbon-containing polymer material is dissolved in distilled water, the porous silica structure is added while stirring, and left for 1 hour or more, more preferably 1 to 3 hours, so that the porous silica structure is coated with the carbon-containing polymer material.

It is more preferable to further include a process of aging at 75 to 85° C. for 3 hours or more, more preferably 3 to 5 hours after coating the porous silica structure with the carbon-containing polymer.

The carbon-containing polymer-coated porous silica structure is evaporated and dried at 100 to 120° C. for 12 hours or more, more preferably 12 to 14 hours.

The dried structure is oxidized by raising the temperature to 180 to 220 ° C, more preferably to 200 ° C at a heating rate of 1 ° C / min in an air atmosphere in order to increase the crosslinking of the carbon-containing polymer, and then maintaining it for 1 to 5 hours. do.

The oxidized structure is carbonized by heat treatment. It is preferable to carbonize by charging nitrogen into a sintering furnace in which nitrogen is purged. The structure is heated to 800 to 1,000° C., more preferably to 900° C. at a heating rate of 5° C./min, and then heat-treated for 5 to 25 hours to carbonize the carbon-containing polymer material. It is more preferable to heat-treat for 20 to 25 hours.

After carbonization, it is naturally cooled to room temperature to prepare a porous silica-carbon structure in which carbon-containing polymers are carbonized.

3. Preparation of porous silica-carbon-carbon wire structure

A porous silica-carbon-carbon wire structure is prepared by growing a carbon wire on the porous silica-carbon structure.

First, 4 to 5% by weight of magnesium (Mg) powder relative to the weight of the porous silica-carbon structure is mixed with the porous silica-carbon structure. Magnesium serves as a catalyst for growth in a wire form by thermal decomposition of carbon materials in a porous silica-carbon structure. Magnesium reduces silica and at the same time is oxidized and converted into MgOx. The local high heat generated at this time melts and rearranges the carbon material, transforming the carbon into a wire form.

The powder mixed with magnesium in the porous silica-carbon structure is heat treated at 600 to 700 ° C for 5 to 7 hours in a nitrogen atmosphere.

The heat-treated sample is pulverized and passed through a sieve of 150 to 250 mesh to obtain a porous silica-carbon-carbon wire structure. It is more preferable to use a 200 mesh sieve.

4. Preparation of mesoporous carbon-carbon wire structure

A mesoporous carbon-carbon wire structure is prepared by removing silica from the porous silica-carbon-carbon wire structure.

As a material for removing silica, hydrofluoric acid (HF) or a strong alkali such as sodium hydroxide (NaOH), potassium hydroxide (KOH), or calcium hydroxide {Ca(OH) ₂ } is used. It is more preferable to use hydrofluoric acid.

Distilled water weighing 8 to 12 times the weight of the solid content of the porous silica-carbon-carbon wire structure is placed in a reaction container, and a substance for removing silica is slowly injected into the distilled water to prepare a hydrofluoric acid solution or a strong alkali solution at a concentration of 15 to 25% by weight. . It is more preferred to prepare a 20% by weight solution.

After slowly injecting the porous silica-carbon-carbon wire structure into the prepared solution, sealing it, and reacting for 12 hours or more, more preferably 12 to 14 hours, to dissolve the silica material in the porous silica-carbon-carbon wire structure. The reaction is preferably carried out while vibrating with a vibrating stirrer.

When the stirring is completed, the solution is removed by filtration, and the solid content is washed 3 to 5 times with distilled water. The separated solid content is dried at 90 to 110 ° C. for 10 to 14 hours to prepare a mesoporous carbon-carbon wire structure.

The mesoporous carbon-carbon wire structure preferably includes mesopores having an average pore size of 3 to 5 nm and a particle size of 80 to 800 nm. It is more preferable that the particle size is 80-500 nm.

5. Preparation of cathode material composition for lithium-sulfur battery

A cathode material composition for a lithium-sulfur battery is prepared by impregnating the mesoporous carbon-carbon wire structure with sulfur.

As sulfur, elemental sulfur is pulverized and used. As a method of pulverizing elemental sulfur, a known method can be used. One example of a method for grinding sulfur is grinding elemental sulfur for 4 to 6 minutes using a mixer with a zirconia ball.

The pulverized sulfur and the mesoporous carbon-carbon wire structure are mixed in a weight ratio of 2 to 4:1 and pulverized. The mixture of sulfur and the mesoporous carbon-carbon wire structure is preferably pulverized by grinding in a mortar for 4 to 6 minutes.

The mixture of the pulverized sulfur and the mesoporous carbon-carbon wire structure is heat-treated at 150 to 160° C. for 10 to 14 hours to impregnate sulfur into the mesoporous carbon-carbon wire structure.

A cathode material composition for a lithium-sulfur battery in which sulfur is impregnated into pores in a mesoporous carbon-carbon wire structure is obtained.

A composition for a cathode material of a lithium-sulfur battery in which a mesoporous carbon-carbon wire structure is impregnated with sulfur is used as a cathode material in a lithium-sulfur battery.

When the positive electrode material composition impregnated with sulfur is used for the mesoporous carbon-carbon wire structure of the present invention, a carbon structure containing mesopores having an average pore size of 3 to 5 nm and a carbon wire grown from the carbon structure including the mesopores A mesoporous carbon-carbon wire structure including a particle size of 80 to 800 nm; A lithium-sulfur battery may be obtained by using a cathode material composition for a lithium-sulfur battery including sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure as a cathode material.

Such a lithium-sulfur battery has a high energy density because a high content of sulfur is supported in the pores inside the mesoporous carbon-carbon wire structure.

The present invention will be described in detail through the following examples. These examples are illustrative of the present invention, but the scope of the present invention is not limited thereto.

<Example 1>

Preparation of mesoporous carbon-carbon wire structure

(1) Preparation of porous silica structure

2 ml of 28 wt% ammonia water, 80 ml of distilled water, 15 ml of organosilane, and 60 ml of TEOS were added in a reactor carrying 1000 g of ethanol, and stirred for 5 hours or more to synthesize a porous silica structure.

After removing the liquid phase of the synthesized silica structure using a centrifuge, the solid content was dried in a drying oven at 100° C. for 12 hours or more.

The dried silica structure was placed in a sintering furnace and heat-treated at 550° C. for 5 hours to remove organic substances present therein, thereby obtaining a porous silica structure.

A SEM image of the porous silica structure having an average diameter of 500 nm prepared as described above is shown in FIG. 1 .

(2) Preparation of porous silica-carbon structure

A porous silica-carbon structure was prepared by coating the prepared porous silica structure with a carbon-containing polymer material.

As the carbon-containing polymer material to be coated on the silica surface, a mixture of phenolic resin and cellulose in a weight ratio of 7:3 was used.

A carbon-containing polymer in an amount of 0.23 times the weight of the porous silica structure was dissolved in distilled water three times the weight of the porous silica structure.

After dissolving the carbon-containing polymer material, the porous silica structure was introduced while stirring, and the surface of the porous silica structure was uniformly coated with the carbon-containing polymer material by aging at 80° C. for 3 hours or more.

The carbon-containing polymer-coated porous silica structure was evaporated and dried at 100 to 120° C. for more than 12 hours.

The dried structure was heated up to 200° C. at a heating rate of 1° C./min in an air atmosphere in order to increase the crosslinking of the carbon-containing polymer material, and then oxidized for 1 hour.

The oxidized structure was charged into a firing furnace in which nitrogen was purged, heated up to 900° C. at a heating rate of 5° C./min, and carbonized by heat treatment for 5 hours.

After carbonization, it was naturally cooled to room temperature to obtain a porous silica-carbon structure in which carbon-containing polymers were carbonized.

An SEM image of the porous silica-carbon structure having an average diameter of 500 nm prepared as described above is shown in FIG. 2 .

(3) Preparation of porous silica-carbon-carbon wire structure

A silica-carbon-carbon wire structure was prepared by growing a carbon wire on the porous silica-carbon structure.

First, 4.5% by weight of magnesium (Mg) powder relative to the weight of the porous silica-carbon structure was mixed. The magnesium-mixed powder was charged into a sintering furnace and heat treated at 650° C. for 6 hours in a nitrogen atmosphere.

The heat-treated sample was pulverized and sieved using a 200 mesh sieve to obtain a porous silica-carbon-carbon wire structure, which is a powder passing through the mesh.

(4) Preparation of porous carbon-carbon wire structure

A porous carbon-carbon wire structure was prepared from the prepared porous silica-carbon-carbon wire structure.

Porous silica-carbon-carbon wire structure After preparing distilled water 10 times the weight of the solid content in the reaction vessel, hydrofluoric acid (Sigma-aldrich, HF 48wt% in H ₂ O, ≥99.99% trace metals basis) was slowly injected into the distilled water to obtain 20 A hydrofluoric acid solution of weight % was prepared. After gradually injecting the porous silica-carbon-carbon wire structure into the hydrofluoric acid solution, sealing it with Teflon tape, and then leaving it in a vibrating shaker for 12 hours or more to dissolve the silica material in the porous silica-carbon-carbon wire structure.

After stirring was completed, the reactant was filtered with filter paper in a plastic separation membrane to remove the solution, and then washed 4 times with distilled water. The separated solid content was placed in a drying oven and dried at 100° C. for 12 hours to prepare a mesoporous carbon-carbon wire structure.

<Example 2>

Preparation of porous silica structures

2 ml of 28 wt% ammonia water, 80 ml of distilled water, 15 ml of organosilane, and 60 ml of TEOS were added in a reactor carrying 1000 g of ethanol, and stirred for 5 hours or more to synthesize a porous silica structure.

After removing the liquid phase of the synthesized silica structure using a centrifuge, the solid content was dried in a drying oven at 100° C. for 12 hours or more.

The dried silica structure was placed in a sintering furnace and heat-treated at 550° C. for 5 hours to remove organic substances present therein, thereby obtaining a porous silica structure.

<Example 3>

Manufacturing of mesoporous carbon structures

A porous silica-carbon structure was prepared in the same manner as in Example 1.

After preparing distilled water 10 times the weight of the solid content of the silica-carbon structure in a reaction vessel, hydrofluoric acid (Sigma-aldrich, HF 48 weight in H ₂ O, ≥99.99% trace metals basis) was slowly injected into the distilled water to obtain a concentration of 20% by weight A hydrofluoric acid solution was prepared. After slowly injecting the porous silica-carbon structure into the prepared 20% hydrofluoric acid solution, sealing it with Teflon tape, and reacting while stirring for 12 hours or more in a vibrating shaker, the silica material in the porous silica-carbon structure was dissolved.

When stirring was completed, the solution was removed using filter paper in a funnel made of plastic, and then washed 4 times with distilled water. The separated solid content was dried in a drying oven at 100° C. for 12 hours to obtain a mesoporous carbon structure.

The SEM image of the mesoporous carbon structure having an average diameter of 500 nm prepared as described above is shown in FIG. 3 . As shown in FIG. 3, the mesoporous carbon structure had a shape in which spherical particles were aggregated.

<Example 4>

Preparation of cathode material composition for lithium-sulfur battery

Elemental sulfur was mixed with zirconia balls and ground for 5 minutes using a thinky mixer.

1.5 g of pulverized sulfur and 0.5 g of the mesoporous carbon-carbon wire structure of Example 1 were mixed and pulverized in a mortar for 5 minutes.

A mixture of pulverized sulfur and the mesoporous carbon-carbon wire structure was put into a hydrothermal synthesis reactor and heat-treated at 155 ° C for 12 hours to impregnate sulfur into the mesoporous carbon-carbon wire structure, which is a cathode material for a lithium-sulfur battery, which is a sulfur-carbon composite. composition was obtained.

<Comparative Example 1>

The mesoporous carbon structure prepared in Example 3 was subjected to subsequent heat treatment at 900° C. for 25 hours.

<Comparative Example 2>

The mesoporous carbon structure prepared in Example 3 was subjected to subsequent heat treatment at 900° C. for 5 hours.

<Comparative Example 3>

The mesoporous carbon structure prepared in Example 3 was subjected to subsequent heat treatment at 400° C. for 25 hours.

<Comparative Example 4>

The carbon structure prepared in Comparative Example 1 was impregnated with sulfur in the same manner as in Example 4 to obtain a sulfur-carbon composite.

<Comparative Example 5>

The carbon structure prepared in Comparative Example 2 was impregnated with sulfur in the same manner as in Example 4 to obtain a sulfur-carbon composite.

<Comparative Example 6>

The carbon structure prepared in Comparative Example 3 was impregnated with sulfur in the same manner as in Example 4 to obtain a sulfur-carbon composite.

[Experimental example]

Experiment method

By BET (Brunauer, Emmett, Teller) analysis, physical properties of the structure, such as specific surface area, pore volume and pore size, nitrogen adsorption/desorption characteristics, and pore distribution were confirmed.

<Experimental Example 1>

Structure and properties of mesoporous carbon-carbon wire structure

The structure of the mesoporous carbon-carbon wire structure prepared in Example 1 was confirmed, and an SEM image of the resulting mesoporous carbon-carbon wire structure is shown in FIG. 4 .

In addition, physical properties of the prepared mesoporous carbon-carbon wire structure were compared with those of the mesoporous carbon structure, and are shown in Table 1 below.

characteristic unit mesopore carbon structure Mesopore carbon-carbon wire structure specific surface area m ² /g 967 960 firearms book g/cm ³ 1.64 1.76 average pore size nm 6.68 4.26

As shown in Table 1, the physical properties of the mesoporous carbon-carbon wire structure were similar to those of the mesoporous carbon structure of Example 3, the specific surface area and pore volume were similar, and the average pore size was slightly reduced.

<Experimental Example 2>

Confirmation of characteristics of porous silica structure according to reaction conditions

The characteristics of the porous silica structure according to various reaction conditions were confirmed as follows.

(1) Confirmation of core size of porous silica structure by reaction time

A porous silica structure was prepared in the same manner as in Example 2, except that the reaction times for synthesizing the porous silica structure were set to 1 hour, 2 hours, and 5 hours, respectively.

The silica core sizes of the three porous silica structures prepared were confirmed, and the resulting SEM images are shown in FIG. 5 . In FIG. 5, (A) has a core size of 100 nm as a result of reacting for 1 hour, (B) has a core size of 300 nm as a result of reacting for 2 hours, and (C) has a core size of 300 nm as a result of reacting for 5 hours. As a result of the staining, the core size was 300 nm.

(2) Confirmation of the size of the porous silica structure according to the amount of reaction catalyst

A porous silica structure was prepared in the same manner as in Example 1, except that the amount of ammonia water as a reaction catalyst was 2% by weight, 5% by weight, 9% by weight and 15% by weight.

The silica core sizes of the four prepared porous silica structures were confirmed, and the resulting SEM images are shown in FIG. 6 . In FIG. 6, (A) is 2% by weight, (B) is 5% by weight, (C) is 9% by weight, and (D) is the result when 15% by weight, and the core size was all 300 nm.

(3) Confirmation of the size of the porous silica structure according to the amount of distilled water

A porous silica structure was prepared in the same manner as in Example 1, except that the amount of distilled water was 3% by weight, 7% by weight, 11% by weight, 15% by weight and 23% by weight.

The silica core sizes of the prepared five porous silica structures were confirmed, and the resulting SEM images are shown in FIG. 7 . In FIG. 7, (A) has a core size of 150 nm as a result of 3% by weight, (B) has a core size of 230 nm as a result of 7% by weight, and (C) is a result of 11% by weight The furnace core size is 300 nm, (D) has a core size of 300 nm as a result of 15% by weight, and (E) has a core size of 300 nm as a result of 23% by weight.

(4) Confirmation of the size of the porous silica structure according to the amount of TEOS

A porous silica structure was prepared in the same manner as in Example 1, except that the amount of TEOS was 2% by weight, 6% by weight and 10% by weight.

The silica core sizes of the three porous silica structures prepared were confirmed, and the resulting SEM images are shown in FIG. 8 . In FIG. 8, (A) has a core size of 80 nm as a result of 2% by weight, (B) has a core size of 300 nm as a result of 6% by weight, and (C) is a result of 10% by weight. The furnace core size was 500 nm.

The result of confirming the change in the size of the silica core of the porous silica structure according to the reaction conditions for the synthesis as described above is shown in FIG. 9.

<Experimental Example 3>

Characterization of porous silica structures according to silica core size

The characteristics of the porous silica structure according to the silica core size were confirmed.

The nitrogen adsorption/desorption characteristics, pore distribution, and physical properties of porous silica structures having core sizes of 80 nm, 300 nm, and 500 nm, respectively, were confirmed.

The resulting nitrogen isotherm and pore distribution are shown in FIG. 10, and the results of confirming the physical properties are shown in FIG. 11 and Table 2 below.

item unit silica core size 80 300 500 specific surface area m ² /g 296 140 140 pore volume cc/g 0.64 0.37 0.36 pore size nm 8.63 10.49 10.24

As shown in the above results, the specific surface area and pore volume properties of the porous silica structure having the smallest silica core size of 80 nm were the best. It is believed that the pores formed between the small particles affected the physical properties of the porous silica structure.

<Experimental Example 4>

Confirmation of characteristics of porous silica structures according to types of surfactants

The characteristics of the porous silica structure according to the type of surfactant used for pore expansion in the preparation of the porous silica structure were confirmed as follows.

Organosilane, Cetyltrimethylammoniumbromide (CTAB), Cetyltrimethylammoniumchloride (CTAC), Divinylbenzene, Cellulose, Phenol resin, and Polyvinylalcohol are used as surfactants for the synthesis of porous silica structures. A porous silica structure was prepared in the same manner as in Example 2 and used as a sample.

(1) Confirmation of the core-shell structure of the porous silica structure

The core-shell structure of the porous silica structure was confirmed, and the resulting SEM image is shown in FIG. 12 .

As confirmed in FIG. 12, the shape of the structure was most uniform when organosilane was used as a surfactant.

(2) Confirmation of characteristics of porous silica structure

Among the porous silica structures, the nitrogen adsorption/desorption characteristics, pore distribution, and physical properties of the porous silica structures prepared using organosilane (C ₁₈ TMS), CTAB, and CTAC were confirmed. For comparison, a 300 nm silica core was used.

The nitrogen isotherm of the core-shell of the porous silica structure is shown in FIG. 13 and the pore distribution is shown in FIG.

In addition, the results of confirming the physical properties of the core-shell of the porous silica structure prepared using organosilane (C ₁₈ TMS), CTAB and CTAC are shown in Table 3 below.

item unit Silica Core-Shell C ₁₈ TMS CTAB CTAC specific surface area m ² /g 472 441 270 pore volume cc/g 0.48 0.36 0.22 pore size nm 4.1 3.2 3.2

As in the above results, the physical properties of the porous silica structure prepared using organosilane as a surfactant were the best.

<Experimental Example 5>

Confirmation of characteristics of porous silica structure according to organosilane ratio

The characteristics of the porous silica structure according to the organosilane ratio used in the preparation of the porous silica structure were confirmed.

A porous silica structure was prepared using organosilane so that the volume ratio of organosilane/TEOS was 0.125, 0.375, and 1, respectively.

(1) Confirmation of core-shell structure of porous silica structure

15 shows an SEM image resulting from confirming the core-shell structure of the porous silica structure.

As confirmed in FIG. 15, when the organic silane ratio was 0.375, the structure of the core-shell of the porous silica structure was the best.

(2) Confirmation of characteristics of porous silica structure

The nitrogen adsorption/desorption characteristics, pore distribution, and physical properties of the porous silica structure were confirmed.

The nitrogen isotherm and pore distribution of the core-shell of the porous silica structure were confirmed, and the results are shown in FIG. 16, and the results of confirming the physical properties of the core-shell of the porous silica structure are shown in Table 4 below.

item unit Silica core-shell (organosilane/TEOS) 0.125 0.375 One specific surface area m ² /g 237 470 397 pore volume cc/g 0.22 0.42 0.38 pore size nm 3.58 4.58 3.65

As in the above results, when the volume ratio of organosilane/TEOS was 0.375, the physical properties of the porous silica structure were the best.

<Experimental Example 6>

Characterization of mesoporous carbon structures according to organosilane ratio

The characteristics of the mesoporous carbon structure according to the mixing ratio of organosilane were confirmed as follows.

Example 3 except that organosilane was used so that the volume ratio of organosilane/TEOS was 0.125, 0.375 and 1, respectively, and 50% by weight of carbon-containing polymer (phenolic resin and cellulose) was used based on the weight of the porous silica structure. Three mesoporous carbon structures were prepared in the same manner and used as samples.

(1) Confirmation of the structure of the mesoporous carbon structure according to the organosilane ratio

The SEM image of the mesoporous carbon structure sample is shown in FIG. 17 . In FIG. 17, (A) shows the case where the organosilane/TEOS volume ratio is 0.125, (B) is 0.375, and (C) is 1.

As shown in FIG. 17, the mesoporous carbon structure has a shape in which spherical particles are aggregated. In the case of the mesoporous carbon structure having an organosilane/TEOS volume ratio of 1, particles having a smaller particle size than the silica template are uniformly mixed and the agglomeration phenomenon is more dense. In addition, when organosilane was used less than TEOS, the surface of the mesoporous carbon structure was constant and concise, but as the ratio increased, the frequency of rough and irregular shapes increased.

(2) Confirmation of nitrogen adsorption/desorption characteristics of the mesoporous carbon structure according to the organosilane ratio

Using the sample, nitrogen adsorption/desorption characteristics of the mesoporous carbon structure according to the organosilane ratio were confirmed.

As a result, the nitrogen isotherm of the mesoporous carbon structure according to the organosilane ratio is shown in FIG. 18.

As shown in the results of FIG. 18, the isothermal shapes of the mesoporous carbon structures prepared for each organosilane ratio showed similar shapes to each other. Similar results were obtained in the porous silica structure, and it can be seen that the mesoporous carbon structure is composed of mesopores and has the form of a porous silica structure that determines the shape of carbon.

(3) Confirmation of the pore distribution of the mesoporous carbon structure according to the organosilane ratio

The pore distribution of the mesoporous carbon structure according to the organosilane ratio was confirmed using the sample.

As a result, the pore distribution curve of the mesoporous carbon structure according to the organosilane ratio is shown in FIG. 19 .

From the results of FIG. 19 , it was confirmed that the adsorbed volume further increased in the pore distribution of 10 nm or more. This can be seen as the effect of the mesopores of 10 nm or more formed as the mesoporous carbon structure is manufactured based on the porous silica structure and the portion composed of silica is melted out during the etching process.

(4) Confirmation of physical properties of mesoporous carbon structure according to organosilane ratio

Using the sample, the physical properties of the mesoporous carbon structure according to the organosilane ratio were confirmed as follows.

20 is a graph showing physical properties of the mesoporous carbon structure by comparing the specific surface area, pore volume, and pore size.

From the graph of FIG. 20 , it can be seen that the pore size is maintained constant even when the organosilane ratio is increased. This phenomenon is due to the effect of the pores formed as the silica is removed during the etching process, and it can be seen that the silica structures forming the walls in the structure provide an average pore size of 3 to 5 nm.

As a result, the mesoporous carbon structure includes not only the pores of the silica structure used as a template but also the pores generated by the removal of the silica material, so that the pore volume per unit weight is more than 10 times greater than that of the silica structure. . Such abundant pore volume provides favorable conditions for carrying the negative electrode active material.

The physical properties of the mesoporous carbon structures derived from the BET analysis results are shown in Table 5 below.

item unit Mesopore carbon structure (organosilane/TEOS volume ratio) 0.125 0.375 One specific surface area m ² /g 1517 1459 1148 pore volume cc/g 1.16 1.28 1.03 pore size nm 2.98 3.44 3.52

As shown in the results of Table 5, when the specific surface area, pore volume, and pore size are all considered, it can be confirmed that the structure is most advantageous for supporting the active material when the organosilane application ratio is 0.375 compared to TEOS.

<Experimental Example 7>

Characterization of mesoporous carbon structures according to the amount of carbon-containing polymers added

The characteristics of the mesoporous carbon structure according to the amount of the carbon-containing polymer coated on the porous silica structure were confirmed as follows.

As the carbon-containing polymer material, a mixture of phenolic resin and cellulose in a weight ratio of 7:3 was used.

Three mesoporous carbon structures were prepared in the same manner as in Example 3 and used as samples, except that the carbon-containing polymer was used in weight ratios of 0.23, 0.5, and 1, respectively, relative to the weight of the solid content of the porous silica structure.

(1) Confirmation of nitrogen adsorption/desorption characteristics of mesoporous carbon structures according to the amount of carbon-containing polymers added

Using the sample, nitrogen adsorption/desorption characteristics of the mesoporous carbon structure according to the addition amount of the carbon-containing polymer were confirmed.

As a result, the nitrogen isotherm of the mesoporous carbon structure according to the addition amount of the carbon-containing polymer is shown in FIG. 21 .

From the results of FIG. 21 , it can be seen that the smaller the addition amount of the carbon-containing polymer, the higher the nitrogen adsorption capacity of the mesoporous carbon structure. In particular, it can be seen that the nitrogen adsorption capacity of the hollow carbon structure when the polymer addition ratio is 1 is significantly reduced.

It is confirmed that this result is because the physical properties of the mesoporous carbon structure have a great influence depending on the amount of the carbon-containing polymer coated in the porous silica structure.

(2) Confirmation of the pore distribution of the mesoporous carbon structure according to the amount of carbon-containing polymers added

The pore distribution of the mesoporous carbon structure according to the addition amount of the carbon-containing polymer material was confirmed using the sample.

As a result, the pore distribution curve of the mesoporous carbon structure according to the addition amount of the carbon-containing polymer is shown in FIG. 22.

Looking at the pore distribution for each sample in the results of FIG. 22, the mesoporous carbon structures in which the addition amount of carbon-containing polymer material was 0.23 and 0.5 had a similar pore distribution, but when the addition amount of carbon-containing polymer material was 1, the pore volume was is rapidly declining.

That is, comparing the case where the addition amount of the carbon-containing polymer material was 0.23 and the case where the amount was 0.5, it could be confirmed that pores of 2 nm or less were reduced while pores of 10 nm or more were enlarged when the amount of the carbon-containing polymer was small. When the addition amount of the carbon-containing polymer material was 1, the pore distribution was generally similar to that of the case where the addition amount of the carbon-containing polymer material was 0.5, but the volume decreased rapidly.

This phenomenon occurs when the amount of the carbon-containing polymer coated on the porous silica structure is more than 0.5, and the porous silica structure is supported in excess of the pore volume provided by the porous silica structure, and the excessively supported polymer extends to the outside surface in addition to the inside of the pores of the porous silica structure. It seems to be because the resin layer is formed thickly and converted to a carbon body with no pores.

(3) Confirmation of physical properties of mesoporous carbon structures according to the amount of carbon-containing polymers added

Using the sample, the physical properties of the mesoporous carbon structure according to the addition amount of the carbon-containing polymer were confirmed.

23 shows a graph comparing the specific surface area, pore volume, and pore size, which are physical properties of the resultant mesoporous carbon structure.

As shown in the graph of FIG. 23, the specific surface area of the mesoporous carbon structure is highest when the addition amount of carbon-containing polymer is 0.5, but the pore volume and pore size are the highest when the addition amount of carbon-containing polymer is small. there is.

Based on this trend, it is speculated that in the step of coating and carbonizing the carbon-containing polymer in the pores of the porous silica structure to form a carbon body, the case where the amount of the carbon-containing polymer is half of the silica solid content further develops micropores. can do.

That is, when the addition amount of the carbon-containing polymer material is 1, it is determined that the carbon-containing polymer material does not completely fill the pore volume and is coated on the pore wall with a thickness of 2 nm or less. However, when the amount of the carbon-containing polymer is smaller than this, it can be assumed that the carbon-containing polymer is coated more thinly on the pore wall to expand the pore volume.

The physical properties of the mesoporous carbon structures derived from the BET analysis results are shown in Table 6 below.

characteristic unit
(unit) Medium pore carbon structure (polymer material/silica weight ratio) 0.23 0.5 One surface area m ² /g 967 1459 586 pore volume cc/g 1.64 1.28 0.33 pore size nm 6.68 3.4 2.3

From the results of Table 6, it can be seen that the physical properties are generally reduced as the content of the carbon-containing polymer, that is, carbon, increases compared to the porous silica structure, and the pore volume, which is a physical property of the provided template, is not effectively utilized can know

In order to manufacture an optimal mesoporous carbon structure for supporting an anode active material for a secondary battery, more favorable conditions can be provided for the pore volume and pore size than the physical properties of the specific surface area.

From these results, it can be seen that the optimal condition of the mesoporous carbon structure for supporting the active material is that the ratio of the polymer material to the silica structure is about 0.23. Under these conditions, it can be confirmed that the pore volume of the carbon structure is 1.64, which can support about 1.5 times or more of the active material of the carbon weight.

<Experimental Example 8>

Characterization of mesoporous carbon structure according to particle size

The characteristics of the mesoporous carbon structure according to the particle size were confirmed.

The structure, nitrogen adsorption/desorption characteristics, pore distribution, and physical properties of the mesoporous carbon structures having particle sizes of 80 nm, 300 nm, and 500 nm, respectively, were confirmed.

The SEM image as a result of confirming the structure is shown in FIG. 24 . 24, (A) is a mesoporous carbon structure with a particle size of 80 nm, (B) is a mesoporous carbon structure with a particle size of 300 nm, and (C) is a SEM image of a mesoporous carbon structure with a particle size of 500 nm.

In addition, the results of confirming the nitrogen isotherm and pore distribution are shown in FIG. 25, and the results of confirming the physical properties are shown in FIG. 25 and Table 7 below.

item unit Particle size of mesoporous carbon structure 80 300 500 surface area m ² /g 936 958 967 pore volume cc/g 1.67 1.31 1.64 pore size nm 7.19 5.5 6.68 Pore 2~10nm nm 1.03 0.39 0.79

As shown in the above results, the physical properties of the mesoporous carbon structure having the smallest silica core of 80 nm were the best.

<Experimental Example 9>

Confirmation of characteristics of mesoporous carbon structure according to heat treatment temperature

The characteristics of the mesoporous carbon structure according to the heat treatment temperature were confirmed.

The structure, nitrogen adsorption/desorption characteristics, pore distribution, and physical properties of the mesoporous carbon structures prepared by heat treatment at 110°C, 400°C, 700°C, and 900°C for 1 hour, respectively, were confirmed.

The SEM image as a result of confirming the structure is shown in FIG. 26 . 26, (A) is a mesoporous carbon structure heat treated at 110 ° C, (B) is a mesoporous carbon structure heat treated at 400 ° C, (C) is a mesoporous carbon structure heat treated at 700 ° C, (D) is 900 This is a SEM image of a mesoporous carbon structure heat-treated at °C.

In addition, the results of confirming the nitrogen isotherm and pore distribution are shown in FIG. 27, and the results of confirming the physical properties are shown in FIG. 27 and Table 8 below.

temperature ℃ 110 400 700 900 surface area m ² /g 936 978 999 1021 pore volume cc/g 1.67 1.84 1.92 2 pore size nm 7.19 7.53 7.7 7.77

As in the above results, the physical properties of the mesoporous carbon structure were the best when the heat treatment temperature was 900 ° C.

When the heat treatment temperature increases, there is no change in the outer structure of the structure, and the nitrogen isotherm and pore distribution form are similar, but the specific surface area, pore volume, and pore physical properties increase, and the pore expands due to the thermal decomposition of carbon forming the pore wall.

<Experimental Example 10>

Confirmation of characteristics of mesoporous carbon structure according to heat treatment time

The characteristics of the mesoporous carbon structure were confirmed during the heat treatment.

The mesoporous carbon structures prepared by heat treatment at 900 ° C for 5 hours, 10 hours, 15 hours, 20 hours and 25 hours were confirmed for nitrogen adsorption/desorption characteristics, pore distribution, physical properties and particle size distribution.

(1) Characteristics according to heat treatment time

The results of confirming the nitrogen isotherm and pore distribution according to the heat treatment time are shown in FIG. 28, and the results of confirming the physical properties are shown in FIG. 28 and Table 9 below.

characteristic unit Heat treatment time at 900℃ 5 10 15 20 25 specific surface area m ² /g 999 1052 1085 1098 1119 pore volume cc/g 1.93 2.06 2.18 2.24 2.33 pore size nm 7.66 7.78 7.98 8.09 8.25

As in the above results, when the heat treatment time was 25 hours, the physical properties of the mesoporous carbon structure were the best.

(2) Particle size distribution characteristics according to heat treatment time

29 shows the result of confirming the particle size distribution of the mesoporous carbon structure according to the heat treatment time.

In FIG. 29, D[3.2] is the surface area moment mean, D[4.3] is the volume moment mean, D[1.0] is the number length mean, and Dv[10 ] indicates the maximum particle size of 10% of the sample volume, Dv[50] indicates the maximum particle size of 50% of the sample volume, and Dv[90] indicates the maximum particle size of 90% of the sample volume.

As shown in the results of FIG. 29, the particle average volume tended to decrease with the heat treatment time.

<Experimental Example 11>

Confirmation of characteristics of carbon structure before sulfur impregnation

The nitrogen isotherms and pore distribution curves of the carbon structures of Example 1 and Comparative Examples 1 to 3 before sulfur impregnation were confirmed, and the results are shown in FIGS. 30 to 33.

30 is a nitrogen isotherm and pore distribution curve of the mesoporous carbon-carbon wire structure of Example 1, FIG. 31 is a nitrogen isotherm and pore distribution curve of the heat-treated mesoporous carbon structure of Comparative Example 1, and FIG. 32 is a comparative example. 2, and FIG. 33 is a nitrogen isotherm and pore distribution curve of the heat-treated mesoporous carbon structure of Comparative Example 3.

In addition, the results of comparing the physical properties of the carbon structures of Example 1 and Comparative Examples 1 to 3 are shown in Table 10 below.

characteristic unit Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 specific surface area m ² /g 1076 1119 999 968 pore volume cc/g 2.24 2.33 1.93 1.84 pore size nm 8.28 8.25 7.66 7.54

Comparative Example 3 is a sample heat-treated at 400° C. for 5 hours without growing a carbon wire, and has basic physical properties of a specific surface area of 968 m ² /g, a pore volume of 1.84 cc/g, and a pore size of 7.54 nm.

Comparative Example 2 was a sample heat-treated at 900 ° C, which is higher than Comparative Example 3, and the specific surface area and pore volume slightly increased to 31 and 0.09, respectively, compared to Comparative Example 3.

Comparative Example 1 was a sample heat-treated for 25 hours at 900 ° C, which is a higher temperature than Comparative Example 3, and compared to Comparative Example 3, the specific surface area and pore volume increased by 151 and 0.49, respectively.

Example 1 is a mesoporous carbon-carbon wire structure in which carbon wires are grown, and the development of pore volume is evident even without subsequent heat treatment, similar to Comparative Example 1 in which heat treatment is performed at 900 ° C. for 25 hours without carbon wire growth showed properties.

This shows that since the conditions for growing the carbon wire contribute to the expansion of the pore volume, when the carbon wire is grown, a separate heat treatment for expanding the pore volume is not required. The larger the pore volume, the larger the amount of sulfur impregnated into the pore, so the pore volume plays an important role in sulfur impregnation.

In addition, the structures of the carbon structures of Example 1 and Comparative Examples 1 to 3 were confirmed and shown in FIGS. 34 to 37.

34 is a SEM image confirming the structure of the mesoporous carbon-carbon wire structure of Example 1, FIG. 35 is an SEM image confirming the structure of the heat-treated mesoporous carbon structure of Comparative Example 1, and FIG. 37 is a SEM image confirming the structure of the heat-treated mesoporous carbon structure of Comparative Example 3.

<Experimental Example 12>

Thermogravimetric analysis (TGA) of sulfur-carbon composites

Thermogravimetric analysis (TGA) was performed on the sulfur-carbon composites of Example 4 and Comparative Examples 4 to 6, and the results are shown in FIG. 38 .

As shown in FIG. 38, the carbon structures of Example 4 and Comparative Example 4 having a large pore volume showed little weight loss and high final yield from 100 ° C or higher. A low weight loss means that sulfur is effectively impregnated into the carbon structure, and a high final yield means that the degree of carbonization due to the heat treatment effect is high, and the degree of carbonization means that the fraction of carbon in the carbon structure is high.

<Experimental Example 13>

XRD analysis of sulfur-carbon composites

XRD analysis was performed on the sulfur-carbon composites of Example 4 and Comparative Examples 4 to 6, and the results are shown in FIG. 39 .

In the graph of FIG. 39, sharp peaks represent solid sulfur peaks, and in the case of Example 4 and Comparative Example 4, which have large pores, it can be seen that almost no sulfur peaks appear. This means that the impregnated sulfur exists inside the carbon structure having a large pore volume.

<Experimental Example 14>

Battery performance evaluation

0.35 g sulfur-carbon composite sample, 0.1 g Super-P, 0.05 g PVDF (sigma), and one 10 mm zirconia ball were put in a mixer container, and 3.6 ml of NMP was additionally added and mixed for 28 minutes using a mixer. As the sulfur-carbon composite samples, the sulfur-carbon composites of Example 4 and Comparative Examples 4 to 6 were used.

The prepared slurry was cast on an aluminum current collector and then dried in an oven at 60° C. for 12 hours.

As an electrolyte, 1M bis(trifluoromethane) is mixed with 1,2-dimethoxyethane and 1,4-dioxolane in a volume ratio of 1:1. Sulfonimide {bis(trifluoromethane)sulfonimide} and 0.2M LiNO ₃ were dissolved and used.

Electrochemical analysis was performed using the CR2032 coin cell prepared as described above. At this time, lithium metal was used as the negative electrode and SV718 (Asahi Kasei) was used as the separator. Life characteristics were evaluated under 0.2C current density after charging and discharging one cycle at 0.1C current density in the voltage range of 1.8 to 2.6V compared to lithium.

The battery performance test results for analyzing the lithium ion charge and discharge performance of the sulfur-carbon composites of Example 4 and Comparative Examples 4 to 6 are shown in FIG. 40 as a battery performance evaluation graph.

The graph of FIG. 40 shows the discharge performance according to the number of charge and discharge in the battery performance test for analyzing the lithium ion charge and discharge performance of the sulfur-carbon composite samples. At this time, the X-axis represents the number of charge and discharge times, and the Y-axis represents the charge-to-discharge performance as coulombic efficiency.

Coulomb efficiency (%) was calculated by Equation 1 below:

[Equation 1]

Coulombic efficiency (%) = 100 × discharge performance / charge performance

From the results of FIG. 40, it can be seen that the performance of the sulfur-carbon composite of Example 4 in which sulfur is effectively supported in the carbon structure is superior to that of the sulfur-carbon composite of Comparative Examples 4 to 6. From these results, it can be seen that the structure of the carbon wire is effective in the movement of electrons generated during discharge.

In addition, from the battery performance evaluation graph of FIG. 40 , the discharge performance for each cycle compared to the discharge performance of the initial one cycle according to the number of charge and discharge cycles was confirmed, and the results are shown in FIG. 41 .

Life characteristics (%) were calculated by Equation 2 below:

[Equation 2]

Life characteristics (%) = 100 × discharge performance (n cycles) / discharge performance (1 cycle)

From the results of FIG. 41, it can be seen that the sulfur-carbon composite of Example 4 having a carbon wire structure has excellent lifespan characteristics. Able to know. This seems to be because the carbon structure of Example 4 having a carbon wire structure helped to improve battery life.

Claims (16)

Preparing a porous silica structure;
preparing a porous silica-carbon structure by coating a surface of the porous silica structure with a carbon-containing polymer material and heat-treating;
preparing a porous silica-carbon-carbon wire structure by growing a carbon wire on the porous silica-carbon structure;
preparing a mesoporous carbon-carbon wire structure by removing silica from the porous silica-carbon-carbon wire structure; and
A method for producing a cathode material composition for a lithium-sulfur battery comprising the step of impregnating the mesoporous carbon-carbon wire structure with sulfur. According to claim 1,
The porous silica structure contains 2 to 10% by weight of TEOS (Tetraethyl orthosilicate), 2 to 15% by weight of ammonia water at a concentration of 20 to 35% by weight, 3 to 25% by weight of distilled water, and 0.14 to 0.5 times the volume of TEOS based on the total weight of the composition. A process according to claim 1 , characterized in that it is produced using a composition comprising a volume of organosilane and the remainder a solvent selected from ethanol and methanol. According to claim 2,
The porous silica structure,
Synthesizing by mixing ammonia water, distilled water, organosilane, and TEOS at a concentration of 20 to 35% by weight in a solvent and stirring for 5 hours or more;
removing the liquid phase, separating only the solid content, and drying at 90 to 110° C. for 12 hours or more; and
A manufacturing method characterized in that produced by a method comprising the step of heat treatment at 500 ~ 600 ℃ for 4 ~ 6 hours. According to claim 1,
The porous silica structure is a manufacturing method, characterized in that the spherical particle size of 80 ~ 700nm. According to claim 1,
The carbon-containing polymer is a mixture of a thermoplastic resin selected from phenolic resin, PVA (polyvinyl alcohol), PAN (polyacrylonitrile), PE (polyethylene), PP (polypropylene), PVC (polyvinylchloride) and PS (polystyrene), and cellulose A manufacturing method characterized in that. According to claim 5,
The thermoplastic resin and the cellulose are mixed in a weight ratio of 6:4 to 8:2. According to claim 1,
The porous silica-carbon structure,
Dissolving 0.2 to 0.5 times the weight of the porous silica structure in distilled water of 2.5 to 3.5 times the weight of the porous silica structure - a polymer material containing carbon;
coating the porous silica structure with the carbon-containing polymer material by dissolving the carbon-containing polymer material and then introducing the porous silica structure and leaving it for at least 1 hour;
evaporating and drying the porous silica structure coated with the carbon-containing polymer at 100 to 120° C. for 12 hours or more;
Oxidizing the dried structure for 1 to 5 hours after heating the dried structure to 180 to 220 ° C at a heating rate of 1 ° C / min in an air atmosphere;
raising the temperature of the oxidized structure to 800 to 1,000° C. at a heating rate of 5° C./min, followed by heat treatment for 5 to 25 hours to carbonize the carbon-containing polymer; and
A manufacturing method characterized in that it is produced by a method comprising the step of natural cooling to room temperature. According to claim 7,
The manufacturing method characterized in that it further comprises the step of aging at 75 ~ 85 ℃ for 3 hours or more after the step of coating the porous silica structure with a carbon-containing polymer material. According to claim 1,
The porous silica-carbon-carbon wire structure,
Mixing 4 to 5% by weight of magnesium (Mg) powder relative to the weight of the porous silica-carbon structure;
heat-treating a powder in which magnesium is mixed in a porous silica-carbon structure at 600 to 700° C. for 5 to 7 hours in a nitrogen atmosphere; and
The manufacturing method characterized in that it is produced by a method comprising the step of obtaining a porous silica-carbon-carbon wire structure, which is a powder passing through a sieve of 150 to 250 mesh size after pulverizing the heat-treated sample. According to claim 1,
The mesoporous carbon-carbon wire structure,
Preparing a 15-25% by weight hydrofluoric acid solution by slowly injecting distilled water into a reaction container with 8 to 12 times the weight of the solid content of the porous silica-carbon-carbon wire structure;
Dissolving the silica material in the porous silica-carbon-carbon wire structure by slowly injecting the porous silica-carbon-carbon wire structure into the hydrofluoric acid solution, sealing it, and reacting for 12 hours or more;
filtering to remove the solution and washing the solid content with distilled water 3 to 5 times; and
A manufacturing method characterized in that it is produced by a method comprising the step of drying the separated solid content at 90 to 110 ° C. for 10 to 14 hours. According to claim 1,
grinding elemental sulfur;
mixing and pulverizing the pulverized sulfur and the mesoporous carbon-carbon wire structure in a weight ratio of 2 to 4:1; and
A manufacturing method characterized by impregnating sulfur into a mesoporous carbon-carbon wire structure by a method comprising heat treatment at 150 to 160 ° C. for 10 to 14 hours. According to claim 1,
The mesoporous carbon-carbon wire structure includes mesopores having an average pore size of 3 to 5 nm and a particle size of 80 to 800 nm. A carbon structure containing mesopores having an average pore size of 3 to 5 nm, and a carbon wire grown from the carbon structure including mesopores, and having a particle size of 80 to 800 nm, and a mesopore carbon-carbon wire structure;
A cathode material composition for a lithium-sulfur battery comprising sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure. According to claim 13,
The cathode material composition for a lithium-sulfur battery, characterized in that the composition for a cathode material for a lithium-sulfur battery is prepared by the method of any one of claims 1 to 11. In a lithium-sulfur battery,
A carbon structure containing mesopores having an average pore size of 3 to 5 nm, and a carbon wire grown from the carbon structure including mesopores, and having a particle size of 80 to 800 nm, and a mesopore carbon-carbon wire structure; A lithium-sulfur battery comprising a cathode material composition for a lithium-sulfur battery comprising sulfur impregnated in the pores of the mesoporous carbon-carbon wire structure as a cathode material. According to claim 15,
A lithium-sulfur battery, characterized in that the composition for a cathode material for a lithium-sulfur battery is prepared by the method of any one of claims 1 to 11.

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