KR20190003077A - Methods of manufacturing of pyroprotein based porous carbon materials and pyroprotein based porous carbon materials maufactured there by - Google Patents

Abstract

A porous carbon material including a plurality of hollow carbon nanoparticles is manufactured by a sol-gel process on a template and a heat treatment process with an alkaline activator. The porous carbon material may exhibit, for example, a reversible capacity of -680 mA h g^-1 when used for a negative electrode of a lithium ion battery including the same. Further, the porous carbon material may exhibit not only stability, for example, even in an operation of more than or equal to 1,000 cycles, but also excellent reversibility while operating at a rapid current speed of 0.1 to 30 A g^-1. Also, a lithium ion battery including a corresponding pyroprotein-based porous carbon material is capable of implementing energy per unit weight of 142.7 W h^-1 at 190 W kg^-1 and output per unit weight of 23,850 W^-1 at 48.1 W h^-1 while maintaining a stable state for, for example, 2,000 times or more charging/discharging cycles.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for producing a porous carbon material based on pyro-protein and a pyro-protein-based porous carbon material produced thereby,

The present invention relates to a method for producing a new porous carbon material and a porous carbon material produced thereby. More specifically, the present invention relates to a method for producing a porous carbon material based on pyroproton, which is used for an electrode of an energy storage device, and a porous carbon material produced thereby.

A macroscopic porous material composed of a nanoscale carbon-based unit structure has excellent mechanical, thermal and physicochemical properties and is attracting attention as an electrode for energy storage devices. Such a porous material has a bulk carbon structure and can have nanometer-scale characteristics while having a wide specific surface area. The large specific surface area enables interelectronic and ionic interactions in the nanometer scale of the material's interior space, and allows rapid charge storage through pseudocapacitive principles. Redox reactions on the surface occur mostly in carbon structures where there are not only external defects but also topological and edge defects. However, the sp ³ carbon structure has poor kinetic problems due to its low electrical conductivity. On the other hand, sp ² carbon resonance structures, which are aromatic hexagonal carbon structures, require additional energy to store electrons on their surfaces. Thus, the sp ² carbon resonance structure has free electrons that exhibit high mobility, but they do not cause redox reactions that occur at the surface. Therefore, in order to have excellent electrochemical performance, it is important to design a carbon structure in which sp ² carbon structure used as an electron path and sp ³ carbon structure serving as a redox host are connected to each other.

On the other hand, silk produced by silk is one of nature's most abundant natural polymers, and more than 700,000 tons of silk is cultivated every year worldwide. The inventors of the present application have found that the silk protein has a? -Sheet structure of about 350 Lt; RTI ID = 0.0 > (BSUs). ≪ / RTI > The resulting carbon bodies are called pyroproteins, which are composed of hexagonal carbon nano-domains with many defects and have excellent electrical conductivity, heteroatoms such as oxygen and nitrogen, which can be places for redox reactions It has a lot of atoms.

'Sol-gel chemistry synthesis' and 'template-based synthesis process' are the most common synthetic processes used to make three-dimensionally interconnected carbon structures. Among them, the 'sol-gel chemical process' is a relatively simple process for producing and drying and carbonizing a highly crosslinked organic gel. This method creates an irregular pore structure, but its pore structure can be measured to some extent. On the other hand, the 'template-based synthesis process' can produce very regular pore structure by controlling porosity. However, the process of making a carbon opaque structure using a template must be carefully performed at various stages, and since this method has a large difference in electrochemical performance depending on the carbon precursor used, There are still difficulties in selecting precursors that can be modified and making them have a regular pore structure in an easy way.

 Although excellent electrochemical performance of electrode materials based on pyro-protein has been studied, research for using them as electrodes in energy storage devices has not been conducted, and in-depth study is needed.

J. Bauer, A. Schroer, R. Schwaiger, O. Kraft, Approaching theoretical strength in glassy carbon nanolates, Nat. Mater. 15 (2016) 438. S. Viond, C.S. Tiwary, P.A. da Silva Autreto, J. Taha-Tijerina, S.A.C. Ozden, Chipara, R. Vajtai, D.S. Galvao, T.N. Narayanan, P.M. Ajayan, Low density three dimensional foam using self-reinforced hybrid two dimensional atomic layers, Nat. Commun. 5 (2014) 4541.

Embodiments of the present invention provide a pyro-protein-based porous carbon material (or 3D interconnected pyroprotein macrostructures, 3D IPMS) which is a pyrolysis product of a silk protein of silkworm silk, and a method for producing the same.

In one embodiment of the present invention, there is provided a method for producing a porous carbon material comprising a plurality of hollow carbon nanoparticles, comprising the steps of: preparing a silk fibroin aqueous solution from which sericin is removed from a silk protein; Adding an alkaline activator to the aqueous silk fibroin solution to adjust the pH; Preparing an aqueous solution of silica nanoparticles; Preparing a mixed solution comprising silica nanoparticles coated with silk fibroin by mixing the pH-adjusted aqueous solution of silk fibroin and the aqueous solution of silica nanoparticles; Applying a mixed solution containing the silica nanoparticles coated with the silk fibroin to a template and then drying to form a carbon material including silk fibroin coated silica nanoparticles; Carbonizing the carbon material comprising the silk fibroin coated silica nanoparticles; And removing the silica nanoparticles from the silica nanoparticles coated with the carbonized silk fibroin to prepare hollow carbon nanoparticles to produce a porous carbon material including a plurality of hollow carbon nanoparticles; Wherein the hollow carbon nanoparticles are adjacent to each other in the porous carbon material.

In an exemplary embodiment, in the porous carbon material, a portion of the plurality of hollow carbon nanoparticles may be laminated.

In an exemplary embodiment, the preparation of the aqueous solution of silk fibroin comprises reacting the regenerated silk fibroin from which the sericin is removed from the silk withdrawn from the cocoons of the silkworm (Bombyx mori) with lithium bromide (LiBr), lithium thiocyanate (LiSCN) , An aqueous N-methylmorpholine N-oxide solution, an aqueous solution of calcium chloride / water / ethanol (CaCl ₂ / H ₂ O / ethanol) and a calcium / methanol nitrate mixture solution (Ca (NO ₃ ) ₂ / methanol ) In at least one solution selected from the group consisting of:

In an exemplary embodiment, 300 to 700 parts by weight of the alkaline activator may be added to 100 parts by weight of the aqueous solution of silk fibroin.

In an exemplary embodiment, 25 to 300 parts by weight of the aqueous solution of silica nanoparticles may be added to 100 parts by weight of the aqueous solution of silk fibroin.

In an exemplary embodiment, the step of carbonizing the carbonaceous material comprising the silk fibroin coated silica nanoparticles may be a heat treatment in an argon environment at a temperature of 600 to 1,000 DEG C for 1 to 3 hours.

In an exemplary embodiment, the step of drying the mixed solution comprising the silk fibroin coated silica nanoparticles may be performed at a temperature ranging from 50 to 100 DEG C for 24 to 60 hours.

In an exemplary embodiment, the silica nanoparticles may have a diameter of 400 to 600 nm.

In an exemplary embodiment, the step of mixing a silk fibroin aqueous solution with the aqueous solution of silica nanoparticles to prepare a mixed solution containing silk fibroin-coated silica nanoparticles may be performed under ultrasonic treatment conditions.

In an exemplary embodiment, the step of removing the silica nanoparticles from the carbonylated silk fibroin coated silica nanoparticles may include treating and removing 10 to 50 weight percent hydrofluoric acid solution.

In another embodiment of the present invention, there is provided a porous carbon material comprising a plurality of hollow carbon nanoparticles, wherein the hollow carbon nanoparticles have a hollow core portion; A carbon thin film surrounding the hollow core portion and containing pyroprotein; And the hollow carbon nanoparticles are provided adjacent to the porous carbon material.

In an exemplary embodiment, the porous carbon material may have a 3-dimentional carbon inverse orpal structure.

In an exemplary embodiment, the hollow core portion may have a diameter of 400 to 600 nm.

In an exemplary embodiment, in the porous carbon material, a portion of the plurality of hollow carbon nanoparticles may be laminated.

In an exemplary embodiment, the porous carbon material may have a thickness of 60 [mu] m or less.

In an exemplary embodiment, the carbon film may have a thickness ranging from 1 to 5 nm.

In an exemplary embodiment, the porous carbon material may be for a cathode of a lithium ion battery.

According to an embodiment of the present invention, a plurality of hollow carbon nanoparticles may be three-dimensionally connected in a nanometer-scale unit structure in a pyrochlore-based porous carbon material. This can be produced through a sol-gel manufacturing process on the template and a heat treatment process involving an alkaline activator.

When a pyrophyll-based porous carbon material thus prepared is used as a negative electrode of a lithium ion battery, for example, a reversible capacity of ~ 680 mA hg ^-1 can be exhibited. In addition, when the porous carbon material based on the pyroprotein is used as a negative electrode of a lithium ion battery, it is stable not only in operation for 1,000 cycles or more, but also operates at a high current speed of 0.1 to 30 A g ^-1 , Lt; / RTI >

In addition, lithium ion batteries including a protein-based porous carbon material with the pi, for example, while maintaining the stable state during the charge / discharge cycle over 2,000, 190 W kg ^-1 at 142.7 W h per unit of weight kg ^-1 Energy can be achieved at an output per unit of weight from 48.1 W h kg ^-1 to 23,850 W kg ^-1 .

1 is a schematic view showing a method of manufacturing a porous carbon material according to an embodiment of the present invention.
FIG. 2 is a photograph of the surface characteristics of a porous carbon material according to an embodiment of the present invention. (C), (d) and (e) illustrate the field emission scanning electron microscopy (SEM) images of the porous carbon material, Field emission transmission electron microscope (FE-TEM) image.
3A-3D are SEM images of a porous carbon material according to the content ratio of silk fibrous: silica nanoparticles, wherein all the unit rods are 2 μm (FIG. 3A: 25 wt% silica nanoparticles, FIG. 3B: 50 wt% of silica nanoparticles, FIG. 3C: 200 wt% of silica nanoparticles, and FIG. 3D: 300 wt% of silica nanoparticles)
4a to 4c are SEM image images of porous carbon materials according to the ratio of silk fibrous: potassium hydroxide, wherein all the unit bars are 2 占 퐉 (Fig. 4a: 100wt% potassium hydroxide; Fig. 4b: Potassium hydroxide, Figure 4c: 1,000 wt% potassium hydroxide).
5A to 5C are graphs showing nitrogen adsorption / desorption curves of a porous carbon material according to a ratio of silk fibrous: potassium hydroxide (Fig. 5A: 100 wt% of potassium hydroxide, Fig. 5B: 500 wt% of potassium hydroxide, : 1,000 wt% of potassium hydroxide).
6 to 6C are graphs showing the pore size distribution of the porous carbon material according to the ratio of silk fibrous: potassium hydroxide (Fig. 6A: 100 wt% of potassium hydroxide, Fig. 6B: 500 wt% of potassium hydroxide, wt% potassium hydroxide).
FIGS. 7A to 7C are SEM images showing structural changes of the porous carbon material according to the final heat treatment temperature, and all the unit bars are 1 μm (FIG. 7A: 600 ° C., FIG. 7B: 700 ° C., FIG.
8 is a SEM image of the fracture surface of the porous carbon material ((a): 700 magnifications, and (b): 5,000 magnifications).
9A is a graph showing the microstructure and surface characteristics of a porous carbon material, specifically, FIG. 9A is a Raman spectrum, FIG. 9B is an XRD pattern, FIG. 9C is a nitrogen adsorption / desorption curve of a porous carbon material, FIG. 9E shows O1s XPS and FIG. 9F shows N1s XPS spectrum.
Figure 10a to 10d are deulyimyeo graph showing the performance of the electrochemical ion battery comprising a porous carbon material, Figure 10a shows a constant current charge and discharge at a current density profile 0.5Ag ^-1, scan of Figure 10b, 0.1 mVs ^-1 FIG. 10C shows the speed performance and reversibility at a current density of 0.5 to 30 Ag ^-1 , and FIG. 10 d shows a lifetime characteristic according to a cycle of 1000 times at a current density of 2 Ag ^-1 .
Deulyimyeo Figure 11a to 11b is a graph showing the performance of the electrochemical ion battery comprising a porous carbon material in a Li / Li ⁺ 1.5 ~ 4.5 V compared to, in particular, Figure 11a is a constant current charge-discharge profile at a current density of 0.3 Ag ^-1 And FIG. 11B shows the speed performance at a current density of 0.3 to 10 Ag ^-1 .
FIG. 12 is a graph showing a level curve of a cathode and an anode of a porous carbon material / nano-structured carbon material (NCM) cell during a constant current charge / discharge cycle.
FIGS. 13A to 13D are graphs showing electrochemical performances of a pull cell including a porous carbon material and a nanostructured carbon material (NCMs) as a cathode and an anode, respectively. represents CV curves at ^-1 mV, Figure 13b shows a constant current charge-discharge profile at a current density of 0.1 ~ 15 Ag ^-1, Figure 13c is a porous carbon material // NCM, PHPNC // TiC, graphene coating LTO // AC, RHDPC-KOH // LTO, ZHTP // Li ₄ Ti ₆ O ₁₂ , and FIG. 13D is a Ragone graph of an energy storage device comprising 2000 cycles of current density at 0.1 Ag ^-1 Graph.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention.

Term Definition

In the embodiment of the present invention, 'pyroprotein' means a carbon structure converted from a protein having a β-sheet structure, and has a sp2 hybrid resonance structure or a hexagonal carbon structure, which is a basic structural unit of carbon . For example, the 'pyroprotein' may be prepared by heating the silk protein of silkworms at a temperature of, for example, 350 ° C or higher.

In the embodiment of the present invention, the term " opal structure " refers to a structure in which six beads surround one bead and three, and one is stacked on top of the other.

In the embodiment of the present invention, 'reverse opal structure' means a structure in which the bead portion of the opal structure exists in an empty form and the empty space between the bead and the bead is filled with material.

In an embodiment of the present invention, a 'semi-ordered inverse opal structure' means that the alignment structure of the bead portion of the inverse opal structure is significantly (about 70% or more) aligned although not fully aligned.

In the embodiment of the present invention, '3D interconnected' means a structure in which hollow nanoparticles are adjacent to each other to form a three-dimensional three-dimensional structure.

Manufacturing method of porous carbon material

According to an embodiment of the present invention, there is provided a method of manufacturing a porous carbon material including a plurality of hollow carbon nanoparticles. The method includes the steps of: preparing a silk fibroin aqueous solution from which sericin is removed from a silk protein; Adding an alkaline activator to the aqueous silk fibroin solution to adjust the pH; Preparing an aqueous solution of silica nanoparticles; preparing a mixed solution comprising silica nanoparticles coated with silk fibroin by mixing the aqueous solution of silk fibroin having pH adjusted and the aqueous solution of silica nanoparticles; Applying a mixed solution containing the silica nanoparticles coated with the silk fibroin to a template and then drying to form a carbon material including silk fibroin coated silica nanoparticles; Carbonizing the carbon material comprising the silk fibroin coated silica nanoparticles; And removing the silica nanoparticles from the silica nanoparticles coated with carbonized silk fibroin to produce a porous carbon material including a plurality of hollow carbon nanoparticles; . ≪ / RTI >

Accordingly, a porous carbon material comprising a plurality of hollow carbon nanoparticles, wherein the hollow carbon nanoparticles have a hollow core portion; A carbon thin film surrounding the hollow core portion and containing pyroprotein; And the hollow carbon nanoparticles may be made of a porous carbon material having a structure adjacent to each other.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view briefly showing a manufacturing method of the porous carbon material. Hereinafter, each step will be described in detail based on FIG.

First, an aqueous solution of silk fibroin from which sericin is removed from the silk protein is prepared (step a).

Specifically, regenerated silk fibroin from which sericin is removed from silk extracted from a cocoon of silkworm (Bombyx mori) is treated with lithium bromide (LiBr), lithium thiocyanate (LiSCN), N-methylmorpholine N-oxide aqueous solution -methylmorpholine N-oxide), calcium chloride / water / ethanol aqueous solution (CaCl ₂ / H ₂ O / ethanol) and calcium nitrate / methanol mixture (Ca (NO ₃ ) ₂ / methanol) An aqueous solution of silk fibroin can be prepared.

Then, an alkaline activator is added to the aqueous solution of silk fibroin to adjust the pH (step b).

At this time, 300 to 700 parts by weight of the alkaline activator may be added to 100 parts by weight of the aqueous solution of silk fibroin. When the alkali activator is contained in an amount of less than 300 parts by weight, agglomeration of silk fibroin may occur, and when added in an amount exceeding 700 parts by weight, the morphology of the finally produced porous carbon material may be inhibited.

In an exemplary embodiment, the alkaline activator may include one or more selected from the group consisting of potassium hydroxide (KOH), lithium hydroxide (LiOH), and sodium hydroxide (NaOH).

In one embodiment, about 400 to 600 parts by weight of the alkaline activator may be added to 100 parts by weight of the aqueous solution of silk fibroin.

Next, an aqueous solution of silica nanoparticles is prepared (step c).

Specifically, the silica nanoparticles can be prepared by dispersing the silica nanoparticles in a solvent through ultrasonic treatment or the like.

On the other hand, the silica nanoparticles may have a diameter of 400 to 600 nm. When the diameter of the silica nanoparticles is less than 400 nm, the porosity of the final formed porous carbon material may be insufficient and the electrical performance may be insufficient. It is difficult to produce a porous carbon material in which carbon nanoparticles are three-dimensionally connected to each other.

Thereafter, the pH-adjusted aqueous solution of the silk fibroin and the aqueous solution of the silica nanoparticles are mixed and stirred to prepare a mixed solution containing silk fibroin-coated silica nanoparticles (step d).

In an exemplary embodiment, 25 to 300 parts by weight of the aqueous solution of silica nanoparticles may be added to 100 parts by weight of the aqueous solution of silk fibroin. When the aqueous solution of the silica nanoparticles is added in an amount of less than 25 parts by weight, the silica nanoparticles may not be smoothly coated with silk fibroin, and the amount of silk fibroin is so large that the porous carbon material is difficult to be produced to have a semiarranged inverted opal structure If the amount exceeds 300 parts by weight, the silk fibroin may not be excessively aggregated, or a plurality of hollow carbon nanoparticles or the like may be adjacent or laminated in the porous carbon material, and the porous carbon material may be easily broken.

In one embodiment, 50 to 170 parts by weight of the aqueous solution of silica nanoparticles may be added to 100 parts by weight of the aqueous solution of silk fibroin.

Meanwhile, the step of mixing and stirring the aqueous solution of silk fibroin with the aqueous solution of the silica nanoparticles can be simply performed by a simple mixing / stirring process under ultrasonic treatment conditions.

Next, a mixed solution containing the silica nanoparticles coated with the silk fibroin is applied to a template and dried to form a carbon material including silica nanoparticles coated with silk fibroin (step e).

In an exemplary embodiment, the step of drying the mixed solution comprising the silk fibroin coated silica nanoparticles on the template may be performed at a temperature ranging from 50 to 100 캜 for 24 to 60 hours.

If the drying step is carried out at a temperature of less than 50 ° C or less than 24 hours, drying may not be easy. If the drying step is carried out at a temperature exceeding 100 ° C or more than 60 hours, the carbon material is over- The physical properties of the formed porous carbon material may be deteriorated.

As the above steps are performed, a plurality of silk fibroin coated silica nanoparticles may be three-dimensionally connected to each other. That is, adjacent hollow carbon nanoparticles are in contact with each other, and some silk fibroin-coated silica nanoparticles are stacked.

Then, the carbon material including the silk fibroin-coated silica nanoparticles is carbonized (step f).

In an exemplary embodiment, the step of carbonizing a film comprising the silk fibroin coated silica nanoparticles may comprise heat treating the film in an argon environment at a temperature of 600-1000 < 0 > C for 1 to 3 hours. Specifically, it is carbonized by heat treatment at a temperature of 700 to 900 ° C for 1 hour and 30 minutes to 2 hours and 30 minutes. If carbonization occurs at too low a temperature and for a short time, carbonization will not be sufficient. If carbonization occurs at too high a temperature and for a long time, the hetero elements will not remain in the nanoparticles.

Subsequently, the silica nanoparticles are removed from the carbon nanofibers coated with carbonized silk fibroin to prepare hollow carbon nanoparticles (step g).

At this time, when removing the silica nanoparticles from the silica nanoparticles coated with the carbonized silk fibroin, 10 to 50% by weight of the hydrofluoric acid solution may be treated and removed.

The carbonized silk fibroin from which the silica nanoparticles have been removed is prepared so as to have a hollow hollow structure with a very thin carbon film, hereinafter referred to as hollow carbon nanoparticles.

That is, the silica nanoparticles coated with a plurality of silk fibroin are formed so as to be three-dimensionally connected to each other in the step (e), and the silica nanoparticles are removed at the step (g). Finally, only the hollow carbon nanoparticles are three- (See FIG. 1). That is, the hollow carbon nanoparticles may have a structure adjacent to each other.

In other words, the hollow carbon nanoparticles have a hollow core portion; And a carbon thin film surrounding the hollow core portion; And the hollow carbon nanoparticles are adjacent to each other, a porous carbon material can be produced.

On the other hand, the hollow carbon nanoparticles have a very thin carbon thin film, wherein the carbon thin film thickness may be about 1 nm to 5 nm.

In an exemplary embodiment, the carbon film comprises a pyroprotein. It is derived from the beta sheet protein structure.

Meanwhile, the porous carbon material (specifically, carbon thin film) may have a 3D inverse opal structure, and more specifically, a semi-aligned 3D inverse opal structure.

Thus, through the above process, the hollow hollow core portion having the hollow interior is obtained. And a carbon thin film surrounding the hollow core and containing pyroprotein. The porous carbon material may include a plurality of hollow carbon nanoparticles.

Porous carbon material

In another embodiment of the present invention, a porous carbon material produced by the above-described production method is provided. The porous carbon material includes a plurality of hollow carbon nanoparticles, and the carbon thin film constituting each of the hollow carbon nanoparticles may contain a pyroprotein to provide a place for insertion and desorption of lithium ions. have. These characteristics make it possible to easily perform a role as a lithium ion storage which can be used as a lithium ion battery.

On the other hand, the carbon thin film has a beta sheet structure before carbonization, and is carbonized into an anisotropically agglomerated nano-sized graphite crystal structure through a heat treatment process.

 The porous carbon material includes a plurality of hollow carbon nanoparticles. In such a porous carbon material, the hollow carbon nanoparticles may be three-dimensionally connected to each other. That is, the hollow carbon nanoparticles may be adjacent to each other, and some or all of the plurality of hollow carbon nanoparticles may be stacked on each other.

In the present invention, the hollow carbon nanoparticles are prepared so as to have a hollow hollow structure with a very thin carbon film. That is, the hollow carbon nanoparticles have a hollow core portion; And a carbon thin film surrounding the hollow core portion and containing pyro-protein; . ≪ / RTI >

In an exemplary embodiment, the hollow carbon nanoparticle thin film is composed not only of hexagonal carbon nano-domains having many defects, but also contains many heteroatoms such as oxygen and nitrogen that can be a redox reaction site Lt; RTI ID = 0.0 > pyrolytic, < / RTI > and therefore can have excellent electrical conductivity.

In an exemplary embodiment, the hollow core portion may have a diameter of 400 to 600 nm. If the diameter is less than 400 nm, the porosity of the final formed porous carbon material may be insufficient and the electrical performance may be insufficient. It is difficult for the porous carbon material having hollow carbon nanoparticles to be three-dimensionally connected to each other to have a stable structure.

On the other hand, the porous carbon material is manufactured to have a thickness of 60 μm or less, specifically, to have a thickness of about 40 μm or less. In an exemplary embodiment, the carbon film may have a thickness ranging from 1 to 5 nm. Thus, it is possible to easily provide a place for inserting and removing lithium ions.

Meanwhile, the porous carbon material may have a 3D inverse opal structure, and more specifically, a semi-aligned 3D inverse opal structure.

In the above-mentioned porous carbon material, a plurality of hollow carbon nanoparticles may be three-dimensionally connected with a nanometer scale unit structure, and the porous carbon material may have a semi-aligned 3D reverse opal structure. In other words, the porous carbon material has an 'inverse opal structure' in which the bead portion exists in an empty form in the opal structure and the material is filled in the void space between the bead and the bead. Although they are not perfectly aligned, Sub-aligned opal structure 'that has a' semi-aligned 'structure. This can easily provide a place for inserting and separating lithium ions, and thus can exhibit a reversible capacity of, for example, ~ 680 mAhg < ^-1 > for a cathode of a lithium ion battery manufactured thereby. In addition, when the porous carbon material based on pyroprotein is used as a negative electrode of a lithium ion battery, it is stable not only in operation for 1,000 cycles or more, but also operates at a high current rate of about 0.1-30 A g ^-1 Can exhibit reversibility.

In addition, the lithium ion battery comprising the pyroprotin-based porous carbon material can be maintained at a stable state for more than 2,000 charge / discharge cycles, for example, at a unit weight of 190.7 kg ^-1 to 142.7 W h kg ^-1 The energy per unit of output at 48.1 W h kg ^-1 to 23,850 W kg ^-1 per unit weight can be achieved.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

 [Example]

[Example 1]

99%) 수용액에 용해시켜, 20 wt%의 재생 실크 피브로인 수용액을 제조하였다. 이후, 이 용액을 Slide-a-Lyzer 투석 카세트 (Pierce, MWCO 3500)를 사용하여 48시간 동안 물에 투석하였다. 그 후, 상기 제조된 재생 실크 피브로인 수용액의 농도가 1 wt%가 되도록 물을 첨가하여 희석하였다. 1 wt% 제조된 재생 실크 피브로인 수용액 20g에 KOH(1g, 95%, Samchun Pure Chemical Co., Ltd., Korea)를 첨가하였다. 또한, 초음파 처리를 통해서 200 mg의 실리카 나노입자를 포함한 20g 수용액을 별도로 제조하였다. 이어서 실리카 나노입자(0.5 micron powder, 99.9%, Alfa Aesar Co., Inc.) 분산액을 재생 실크 피브로인 수용액에 붓고 강하게 혼합하여 30분간 교반한 후, 혼합용액을 테플론 접시에 넣고 80℃ 오븐에서 48시간 동안 건조하여, 탄소 박막 재생 실크 피브로인이 코팅된 실리카 나노입자를 포함하는 필름을 수득하였다.Silkworm silk was boiled in Na ₂ CO ₃ aqueous solution (OCI company, 99%, 0.02 M) for 30 minutes and completely washed with distilled water to remove sericin proteins that function as adhesive and coatings to produce regenerated silk fibroin. Thereafter, the regenerated silk fibroin was exposed to 9.3 M lithium bromide (LiBr) (Sigma-Aldrich,

99%) aqueous solution to prepare a 20 wt% aqueous solution of regenerated silk fibroin. The solution was then dialyzed against water using a Slide-a-Lyzer dialysis cassette (Pierce, MWCO 3500) for 48 hours. Thereafter, water was added to dilute the regenerated silk fibroin solution so that the concentration of the aqueous solution of regenerated silk fibroin was 1 wt%. KOH (1 g, 95%, Samchun Pure Chemical Co., Ltd., Korea) was added to 20 g of the aqueous solution of regenerated silk fibroin prepared by 1 wt%. A 20 g aqueous solution containing 200 mg of silica nanoparticles was separately prepared through ultrasonic treatment. The dispersion of silica nanoparticles (0.5 micron powder, 99.9%, Alfa Aesar Co., Inc.) was then poured into an aqueous solution of regenerated silk fibroin and stirred vigorously for 30 minutes. The mixed solution was then placed in a Teflon dish To obtain a film containing silica nanoparticles coated with carbon thin film regeneration silk fibroin.

Then, the film was carbonized by heating from room temperature to 700 DEG C at a rate of 10 DEG C min under an argon condition of 200 mL / min. Thereafter, the carbonized film was treated with a solution of 30 wt% hydrofluoric acid (48%, Dae Jung Chemical & Metals Co., Ltd., Korea) to remove the silica nanoparticles, and then washed with water and ethanol to prepare a porous carbon material . The porous carbon material was then stored in a vacuum oven at 30 占 폚.

[Example 2]

In Example 1, the same process was performed except that the content of KOH was 0.2g, to prepare a porous carbon material.

[Example 3]

In Example 1, the same process was performed except that the content of KOH was 2g, to prepare a porous carbon material.

[Example 4]

In Example 1, a porous carbon material was prepared by performing the same process except that the content of silica nanoparticles in the 20 g aqueous solution containing silica nanoparticles was 50 mg.

[Example 5]

In Example 1, a porous carbon material was prepared by performing the same process except that the content of silica nanoparticles was 100 mg in a 20 g aqueous solution containing silica nanoparticles.

[Example 6]

In Example 1, a porous carbon material was prepared by carrying out the same process except that the content of silica nanoparticles was 400 mg in a 20 g aqueous solution containing silica nanoparticles.

[Example 7]

In Example 1, a porous carbon material was prepared by performing the same process except that the content of silica nanoparticles was 600 mg in a 20 g aqueous solution containing silica nanoparticles.

[Example 8]

In Example 1, the same process was carried out to prepare a porous carbon material, except that the film was heated from room temperature to 350 占 폚 at a rate of 10 占 min under an argon condition of 200 ml / min.

[Example 9]

In Example 1, the same process was carried out to prepare a porous carbon material, except that the film was heated from room temperature to 500 DEG C at a rate of 10 DEG C min under an argon condition of 200 mL / min.

[Example 10]

In Example 1, the same process was performed except that the film was heated from room temperature to 600 ° C at a rate of 10 ° C min under an argon condition of 200 ml / min, to produce a porous carbon material.

[Example 11]

In Example 1, the same process was carried out to prepare a porous carbon material, except that the film was heated from room temperature to 800 DEG C at a rate of 10 DEG C min under an argon condition of 200 mL / min.

[ Experimental Example ]

Experimental and measurement equipment

The morphology of the sample was observed through a scanning electron microscope (FE-SEM, S-4300SE, Hitachi, Japan) and a transmission electron microscope (FE-TEM, JEM2100F, JEOL, Japan). Raman spectra were measured using a continuous wave linearly polarized laser (514.5 nm, 2.41 eV, 16 mW). The laser beam was focused using a magnification 100 objective lens, resulting in ~ 1 탆 diameter spots. The collection time and the number of cycles were collected for 10 seconds and 3 cycles, respectively. X-ray diffraction analysis (XRD, Rigaku DMAX 2500) was performed using Cu-K? Radiation (? = 0.154 nm) at 40 kV and 100 mA. The chemical composition of the samples was investigated by photoelectron spectroscopy (XPS, PHI 5700 ESCA, USA) using monochromatic Al Kα radiation (hυ = 1,486.6 eV). The pore structure of the sample was analyzed by nitrogen adsorption and desorption isotherms obtained using a surface area and porosity analyzer (Tristar, Micromeritics, USA) at -196 ° C. The electrical conductivity of the porous carbon material was measured using an electric conductivity meter (Loresta GP, Mitsubishi Chemical, Japan).

[Experimental Example 1: Characteristic Analysis of Porous Carbon Material]

(1-1) Review of schematic morphology of porous carbon materials

 Figure 2 shows the morphology of the porous carbon material and the plurality of hollow carbon nanoparticles contained therein. In the FE-SEM images of FIGS. 2 (a) and 2 (b), a semi-aligned 3D inverse opal structure connected to each other over a wide range can be confirmed. This structure consists of aqueous phase silk nanoparticles and silk fibrous, because of their amphiphilic nature, silk fibrous is spontaneously coated on silk nanoparticles in aqueous solution.

In the present invention, potassium hydroxide is added to the aqueous solution of silk protein, at which time the gelation of the meta-stable silk fibrous is inhibited and the silk fibrous is more voluminously coated on the silica nanoparticles. It was also confirmed that potassium hydroxide contributes to formation of defective basic structure units (BSUs) when an aqueous solution containing a silk fibrous solution and silica nanoparticles is heated.

On the other hand, the microstructure of the porous carbon material was observed through the FE-TEM, and it was found that the hollow carbon nanoparticles in the porous carbon material consisted of a thin film of carbon nanotubes (pyro-protein layer 1 (c)). Further, it was confirmed that the carbon hexagonal structure is not 100% aligned in a wide range, and thus it has an amorphous structure (FIG. 1 (d)).

(1-2) Consideration of optimum range of mixing ratio of silk fibrous, silica nanoparticles and potassium hydroxide and optimal carbonization temperature (final heat treatment temperature)

1) First, the structure of the porous carbon material according to the mixing ratio of silk fibrous and silica nanoparticles was observed and shown in FIGS. 3A to 3D.

3a-3d are SEM images of porous carbon materials according to the content ratio of silk fibrous: silica nanoparticles (Fig. 3a: 25 wt% silica nanoparticles (Example 4), Fig. 3b: 50 wt% silica (Example 5), Fig. 3c: 200 wt% of silica nanoparticles (Example 6), and Fig. 3d: 300 wt% of silica nanoparticles (Example 7)).

As shown in FIGS. 3A to 3C, a silk protein to SNS ratio of about 25-300 wt% is most suitable for the formation of the structure, and when about 100 parts by weight or less of the silica nanoparticles are used for the silk protein weight portion, Respectively.

2) The structure of the porous carbon material according to the mixing ratio of silk fibrous and potassium hydroxide was observed and shown in Figs. 4A to 4C.

4A-4C are SEM images of a porous carbon material according to the ratio of silk fibrous: potassium hydroxide, wherein all the unit bars are 2 μm (Fig. 4a: 100 wt% potassium hydroxide (Example 2) 500 wt% potassium hydroxide (Example 1), and Fig. 4C: 1000 wt% potassium hydroxide (Example 3)). 5A to 5C are graphs showing nitrogen adsorption / desorption curves of a porous carbon material according to the ratio of silk fibrous: potassium hydroxide (Fig. 5A: 100 wt% of potassium hydroxide (Example 2), Fig. 5B: Potassium hydroxide (Example 1), FIG. 5C: 1000 wt% potassium hydroxide (Example 3)). 6A to 6C are graphs showing the pore size distribution of the porous carbon material according to the ratio of silk fibrous: potassium hydroxide (Fig. 6A: 100 wt% potassium hydroxide (Example 2), Fig. 6B: 500 wt% potassium hydroxide (Example 1), Fig. 6C: 1000 wt% of potassium hydroxide (Example 3)). Referring to FIGS. 4A to 6C, it can be seen that when excess potassium hydroxide is used, the structure is somewhat damaged, but the specific surface area or the pore structure is not largely changed. It was also confirmed that the case of using about 500 parts by weight of potassium hydroxide with respect to 100 parts by weight of silk fibrein was the most optimum.

3) On the other hand, it is judged that the carbonization temperature also affects the morphology of the porous carbon material, and the structural change of the porous carbon material according to the final heat treatment temperature is observed and shown in FIGS. 7A to 7C. Figs. 7A to 7C are SEM images showing structural changes of the porous carbon material according to the final heat treatment temperature, and all the unit rods are 1 mu m (Fig. 7A: 600 DEG C (Example 10) ), Fig. 7C: 800 DEG C (Example 11)).

As shown in FIGS. 7A to 7C, the porous carbon material fabricated at about 700 DEG C has the best morphology among all the samples, and through this process, about 100 wt% or less of silk fibrous large silica nano- The ratio of the particles to the silk protein to potassium hydroxide ratio of less than about 500 wt% was found to be optimal. FIG. 8 shows an SEM image of the fracture surface of the porous carbon material, showing that the thickness of the porous carbon material is about 40 μm or less, and a plurality of hollow carbon nanoparticles are sub-aligned in the inner region

(1-3) Structural analysis using Raman spectroscopy and X-ray diffraction (XRD)

Raman spectroscopy and X-ray diffraction (XRD) were used to analyze the specific structural changes of the porous carbon material according to various carbonization temperatures (Figs. 9a to 9f)

As can be seen in Figure 9a, distinct D and G bands can be identified in the Raman spectra of the prepared porous carbon materials (Examples 8-11 and Example 1) at various heat treatment temperatures from 350 ° C to 800 ° C. The D band and the G band correspond to the disorder of the hexagonal aromatic ring and the sp ² resonance structure of the hexagonal ring carbon, respectively. The ratio of D band to G band (I _D / I _G ) ranges from 0.81 to 0.93, indicating that the hexagonal carbon structure of the hollow carbon particles in porous carbon materials is several nanometers in size. Also, in the XRD pattern of Figure 9b, the porous carbon material of the present invention exhibits a very wide graphite (002) pattern, indicating that the porous carbon material has a poor graphitic stacking arrangement.

(1-4) Porosity Characteristic Analysis

Surface properties of the porous carbon materials are shown in Table 1 below. The results of measurement of the surface characteristics of the porous carbon material by X-ray photoelectron spectroscopy (XPS) are also shown in Table 1 below. The specific surface area of micropores (S _MIC) and mesopores (S _MESO) are gradually increased depending on the temperature of carbonization heat treatment temperature. This is due to the activation of strong potassium hydroxide (KOH) at high temperatures. The specific surface area of the porous carbon material prepared at a temperature of about 700 ° C is 411 m ² g ^-1 and the S _MIC and S _MESO are 268 and 143 m ² g ^-1, respectively. Nitrogen adsorption and desorption isotherms provide more specific information on the pore structure of the porous carbon material.

9C, isotherms are in the form of IUPAC Type-I and Type-II hybrids, showing micropore and mesoporous structures. Adsorption at isolated sites or nitrogen adsorption at open sample surfaces generally occurs at low relative pressures (<0.02). The adsorption of large amounts of nitrogen (~ 100 cm ³ g ^-1 ) at low relative pressures indicates that the porous carbon material has a large surface area. Also, the pore size distribution shows that most of the pore diameters are several nanometers.

Example No. 2. Temperature
(° C) BET (m ² / g) XPS (at.%) Electrical conductivity
(S / cm- ¹ ) S _BET S _MIC S _MESO C O N Pyridinic Pyridonic
/ pyrrolic Quat
ernary N-oxide 8 350 130 85 45 67.8 18.8 13.4
11.37 82.74 0.60 5.29 1.6X10 ^-3 9 500 165 99 66 74.8 14.3 10.9
33.53 60.18 0.61 5.68 8.7X10 ^-3 10 600 323 177 146 79.6 11.1 9.3
44.34 42.98 2.67 10.01 3.5X10 ^-1 One 700 411 268 143 84.5 8.1 7.4
19.46 66.63 4.86 9.05 2.8X10 ⁰ 11 800 429 298 131 85.3 10.4 4.3
22.54 58.84 6.28 12.33 2.5X10 ⁰

Looking at these, it can be seen that a large number of oxygen and nitrogen heteroatoms were introduced to the surface of the porous carbon material, and then the amount thereof was reduced by increasing the heat treatment temperature. The peaks corresponding to CC, CO / CN and C = O bonds were observed at 284.9, 286.4 and 288.7 eV, respectively, in the XPS C 1s spectrum of the porous carbon material heat-treated at 700 ° C. In the XPS O 1s spectrum, peaks corresponding to CO and C = O bonds were observed at 533.0 and 531.2 eV, respectively. Nitrogen atoms, including pyridinic nitrogen, pyridonic and / or pyrrolic nitrogen, quaternary nitrogen and nitrogen oxides, have four different configurations centered at 398.3, 400.1, 401.5, and 403.2 eV, respectively. Nitrogen structures such as pyridinic, pyridonic, and pyrrolic nitrogen play an important role in pseudocapacitive lithium ion storage in the cathode potential region. The porous carbon material prepared at 700 ℃ has the highest ring structure nitrogen ratio among all samples except those generated at 350 ℃. Such oxidation-reduction active nitrogen atoms can increase the capacity and improve the electrical conductivity through the N-type doping effect. It was confirmed that the porous carbon material prepared at 700 ° C showed the highest electrical conductivity among all samples (~ 2.8 S cm ^-1 ). This value slightly higher than 2.5 S cm ^-1 supports the effect of the nitrogen dopant on electrical properties.

[Experimental Example 2: Analysis of electrochemical characteristics of porous carbon material]

The electrochemical properties of the porous carbon materials were analyzed using Wonatech automatic battery cycler and CR2032 type coin cell. The coin cell was assembled in an argon-filled glove box to make a half-cell, a porous carbon material (Example 1) was used as the working electrode, a metallic Li foil was used as a reference electrode and a counter electrode Respectively. 1 M LiPF6 (Aldrich, 99.99%) was dissolved in a solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (1: 1 v / v) and used as a lithium ion battery electrolyte. A glass microfiber filter (GF / F, Whatman) was used as the separation membrane. The working electrode was prepared by punching a porous carbon material into a hole with a diameter of 1/2 inch. The loading of the active material was about 1 mg cm ^-2 and the total electrode weight was about 1-2 mg.

To test the half-cell, it was cycled from 0.01 to 3.0 V versus Li / Li + at various currents and 1.5 to 4.5 V versus Li / Li ⁺ at a constant current.

Referring to FIG. 10a, the constant current discharge / charge profile characterized in the voltage range of 0.01 to 3.00 V versus Li / Li ⁺ shows the lithium ion storage behavior of the porous carbon material without a definite plateau section, Indicating no phase separation or creation of a new phase during the charging process. In addition, various defects on the surface of the electrode can be a host of redox through a single phase reaction in the negative voltage range.

In addition, as shown in FIGS. 2 (d) and 2 (e) and FIGS. 9 (a) and 9 (b), the porous carbon material has a hexagonal carbon structure with many defects and a large number of redox active nitrogen atoms exist on the surface. Thus, it is judged that the reversible capacity of ~ 680 Ma hg- ¹ is obtained at a current density of 500 mA g ^-1 .

Referring again to FIG. 10a, the cyclic voltammetric (CV) curve of the porous carbon material exhibits an irreversible decrease peak at 0.74 V versus Li / Li ⁺ of the first cycle, A solid electrolyte interface (SEI) film is formed. The large decrease peak corresponds to the high irreversible capacity in the first constant current discharge profile as shown in FIG. 10A. This indicates that the porous carbon material has a wide specific surface area having electrical activity. The subsequent CV curve represents an electrochemical double layer without redox pair, indicating that the charge is stored on the surface of the porous carbon material through chemical adsorption or physical adsorption. I tried to make a little more such storage behavior at different sweep rates of 0.1 ~ 50 mVs ^-1 (Fig. 10b), the peak current of the curve is increased with the sweep speed, and can be mathematically represented as i = ^b av . Where a and b are adjustable values. For charge storage by diffusion, the b value is close to 0.5. In contrast, the b value is close to 1 for charge storage at the surface. The average value of b is ~ 0.88, indicating that the charge is stored rapidly on the surface. The porous carbon material of the present invention exhibits excellent storage characteristics at an excellent current rate, and in particular, at a current speed of 10 A g ^-1 or more. This is because concentration polarization is reduced due to well-ordered pore structure (FIG. 10c). Referring to FIG. 10c, a capacity per unit weight of ~ 230 mA hg ^-1 is maintained even when a fast current rate of 30 A g ^-1 is used. Also, upon returning to a current rate of 0.5 A g &lt; ^-1 &gt; after 90 cycles, the initial capacity of the porous carbon material is restored and exhibits good reversibility. On the other hand, the life of the porous carbon material (cycle) to measure the performance naetneunde shown in Figure 10d proceeds to the test at a current rate A 2 g ^-1 over 1,000 continuous cycles, after 1000 cycles, the ~ 412 mA hg ^-1 The capacity per unit weight was measured and a coulombic efficiency of almost 100% was observed, indicating good lifetime stability of the porous carbon material.

[Experimental Example 3: Analysis of electrochemical characteristics of full cell using porous carbon material]

To demonstrate the role of the porous carbon material as a cathode of a lithium ion battery, a full cell was assembled with a porous carbon material.

Specifically, to make a pull cell, a CR2032 type coin cell was assembled in a glove box in an argon environment. A porous carbon material (Example 1) was used as the working electrode, and a metal Li foil was used as a reference electrode and a counter electrode. 1 M LiPF ₆ (Aldrich, 99.99%) was dissolved in a solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (1: 1 v / v) and used as a lithium ion battery electrolyte. A glass microfiber filter (GF / F, Whatman) was used as the separation membrane. A porous carbon material of 1/2 inch diameter was used as the working electrode. The loading of the active material was about 1 mg cm ^-2 and the total electrode weight (both negative and positive) was 4-5 mg.

The cathodes and anodes were cycled at constant current between 0 and 4.2 V at various currents. Further, to assemble the pull cells, the cathode and the anode were preliminarily operated for 30 cycles with Li metal, and the starting potential of both electrodes was controlled to 1.5 V relative to Li / Li ⁺ .

On the other hand, nanocrystalline carbon material (NCM) was selected as a cathode material based on the surface-activated redox reaction after adjusting the energy and kinetic energy of the pull cell system. This electrochemical performance of the NCM anode is shown in FIGS. 11A and 11B. It can be seen that the NCM anode has a high rate characteristic as well as a reversible capacity of 205 mA hg ^-1 at a current rate of 0.3 A g ^-1 .

 A full-cell (porous carbonaceous material // NCM) device was assembled after pre-operating the Li metal electrode of the half-cell, and the design strategy was depicted in FIG. The cathode and anode voltages were adjusted to 1.5 V versus Li / Li + via charge injection. In this configuration, the cathode and the anode operate in the voltage range of 0.0-1.5 V and 1.5-4.2 V, respectively.

Referring to FIG. 13A, the CV curve of a pull cell (porous carbon material // NCM) exhibits a nearly rectangular shape in a voltage range of 1.5 to 4.2 V, indicating a capacitive charge storage behavior. In addition, the large area of the CV graph represents a high energy characteristic of the porous carbon material. As the scan speed increases, the overall shape remains, indicating that the cathode and anode pairs are well balanced between energy and kinetic. A constant current charge / discharge test was performed at various currents of 0.1 to 15 A g &lt; ^{-1 &} gt ;, and shown in FIG. 13B. Profiles measured at different currents showed linearity over a wide operating voltage range, as is the trend of CV curves.

Had an average voltage of 1.90 V at a current density of 0.1 A g ^-1 and had a capacity of ~ 75.3 mA hg ^-1 . This value indicates that the porous carbonaceous material / NCM device has an energy of 142.7 W h kg ^-1 at an output of 190 W kg ^-1 . As the current density increases from 0.1 to 4 A g ^-1 , the capacity gradually decreases and the average voltage increases. At a current density of 4 A g ^-1 , the capacity and average voltage were 44.0 mA hg ^-1 and 2.06 V, respectively. These values correspond to an energy of 90.6 W h kg ^-1 at an output of 8,240 W kg ^-1 . This is another example of the excellent high speed characteristics of a pull cell containing a porous carbon material, the output value is ~ 43.3 times higher than the initial value, but the energy is only reduced by 37%. In addition, this high output value is 23,850 W g ^-1 , which is several times higher than the supercapacitor output at an energy of 48.1 W h kg ^-1 . Details of the electrochemical performance of the pull cells containing the porous carbon material are given in Table 2.

Current density
(A / g) Volume
(mAh / g) Average voltage
(V) Output energy
(Wh / kg) Print
(W / kg) 0.1 75.3 1.90 142.7 190 0.2 70.1 1.93 134.9 386 0.5 62.9 1.95 122.6 975 One 56.1 2.00 112.3 2,000 2 49.7 2.06 102.3 4,120 4 44.0 2.06 90.6 8,240 6 40.5 1.99 80.8 11,940 8 37.6 1.91 71.8 15,280 10 35.4 1.84 65.0 18,400 12.5 33.0 1.71 56.3 21,375 15 30.2 1.59 48.1 23,850

13C shows several energy storage devices such as porous carbon material // NCM, PHPNC // TiC, LTO // AC wound with graphene, RHDPC-KOH // LTO, ZHTP // Li ₄ Ti ₆ O ₁₂ Of the lagoon chart. As a result, it was confirmed that the energy storage device of the porous carbon material // NCM structure has excellent energy and power characteristics and exhibits a stable periodic performance with a coulombic efficiency of 100% at over 2,000 cycles. Referring to FIG. 13d, it was confirmed that a capacity maintenance rate of ~ 86.5% was achieved after 2,000 cycles, demonstrating excellent cycling performance of the porous carbon material // NCM device.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of protection of the present invention as long as it is obvious to those skilled in the art.

Claims (17)

A method for producing a porous carbon material comprising a plurality of hollow carbon nanoparticles,
Preparing a silk fibroin aqueous solution from which sericin is removed from the silk protein;
Adding an alkaline activator to the aqueous silk fibroin solution to adjust the pH;
Preparing an aqueous solution of silica nanoparticles;
Preparing a mixed solution comprising silica nanoparticles coated with silk fibroin by mixing the pH-adjusted aqueous solution of silk fibroin and the aqueous solution of silica nanoparticles;
Applying a mixed solution containing the silica nanoparticles coated with the silk fibroin to a template and then drying to form a carbon material including silk fibroin coated silica nanoparticles;
Carbonizing the carbon material comprising the silk fibroin coated silica nanoparticles; And
Removing the silica nanoparticles from the silica nanoparticles coated with the carbonized silk fibroin to prepare hollow carbon nanoparticles to produce a porous carbon material including a plurality of hollow carbon nanoparticles; Lt; / RTI &gt;
Wherein the hollow carbon nanoparticles are adjacent to each other in the porous carbon material. The method according to claim 1,
In the porous carbon material, a part of the plurality of hollow carbon nano-particles is laminated. The method according to claim 1,
The preparation of the silk fibroin aqueous solution,
Recycled silk fibroin from sericin removed from silk extracted from cocoon of Bombyx mori was treated with lithium bromide (LiBr), lithium thiocyanate (LiSCN), N-methylmorpholine N-oxide solution in at least one solution selected from the group consisting of an aqueous solution of calcium chloride / water, an aqueous solution of calcium chloride / water / ethanol (CaCl ₂ / H ₂ O / ethanol) and a mixture of calcium nitrate / methanol (Ca (NO ₃ ) ₂ / methanol) Wherein the porous carbon material is a porous carbon material. The method according to claim 1,
Wherein 300 to 700 parts by weight of the alkaline activator is added to 100 parts by weight of the aqueous silk fibroin solution. The method according to claim 1,
Wherein 25 to 300 parts by weight of the aqueous solution of the silica nanoparticles is added to 100 parts by weight of the aqueous solution of silk fibroin. The method according to claim 1,
Wherein the step of carbonizing the carbon material comprising the silica nanoparticles coated with the silk fibroin is a heat treatment in an argon environment at a temperature of 600 to 1,000 DEG C for 1 to 3 hours. The method according to claim 1,
Wherein the step of drying the mixed solution including the silk fibroin coated silica nanoparticles is performed at a temperature ranging from 50 to 100 DEG C for 24 to 60 hours. The method according to claim 1,
Wherein the silica nanoparticles have a diameter of 400 to 600 nm. The method according to claim 1,
Wherein the step of mixing the silk fibroin aqueous solution with the aqueous solution of silica nanoparticles to prepare a mixed solution comprising silica nanoparticles coated with silk fibroin is performed under ultrasonic treatment conditions. The method according to claim 1,
Wherein removing the silica nanoparticles from the carbon nanofibers coated with carbonized silk fibroin comprises treating and removing 10 to 50 weight percent hydrofluoric acid solution. A porous carbon material comprising a plurality of hollow carbon nanoparticles,
The hollow carbon nano-particles may include a hollow core part; And a carbon thin film surrounding the hollow core portion and containing pyroprotein,
Hollow carbon nanoparticles are adjacent, porous carbon materials. 12. The method of claim 11,
Said porous carbon material having a 3-dimentional carbon inverse orpal structure. 12. The method of claim 11,
Wherein the hollow core portion has a diameter of 400 to 600 nm. 12. The method of claim 11,
In the porous carbon material, a part of the plurality of hollow carbon nanoparticles is laminated. 12. The method of claim 11,
Wherein the porous carbon material has a thickness of 60 占 퐉 or less. 12. The method of claim 11,
Wherein the carbon thin film has a thickness in the range of 1 to 5 nm. 12. The method of claim 11,
The porous carbon material is a porous carbon material for a cathode of a lithium ion battery.

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