KR20200017070A - Core―shell structure comprising inorganic particle and carbon, and method of fabricating thereof - Google Patents

Abstract

The present invention is to manufacture a silicon-carbon composite particle material which, by utilizing a technique of trapping a plurality of silicon fine particles inside a polymer base material, can solve low initial efficiency problem due to a large surface area of a core-shell structure of an existing single silicon particle-carbon composition, while exhibiting stable lifespan characteristics. Especially, a technique of the present invention can easily control number density of inorganic fine particles contained in the polymer base material, and can be utilized as a high-performance secondary battery electrode material since high density integration is possible.

Description

Core-shell structure comprising inorganic fine particles and carbon and a method for manufacturing the same {CORE-SHELL STRUCTURE COMPRISING INORGANIC PARTICLE AND CARBON, AND METHOD OF FABRICATING THEREOF}

The present invention relates to a core-shell structure comprising inorganic fine particles and carbon, and also to a method for producing a core-shell structure comprising such inorganic fine particles and carbon.

Silicon fine particles, which are high-capacity negative electrode materials of lithium secondary batteries, are restricted from commercial use due to structural damage due to volume expansion despite high performance characteristics.

Therefore, methods for preventing structural damage due to volume expansion during battery operation by including buffering voids in the electrode material have been proposed. As a representative method for this, a core-shell structured technology including one silicon fine particle in a shell made of carbon has been developed. However, this structure has a low initial efficiency characteristic due to an increase in irreversible reaction with lithium ions due to its excessively large surface area characteristics, which still has limitations in commercialization.

In general, the technique of confining the fine particles in the polymer has been used a method in which the particles are randomly included in the polymer in the process of dispersing the particles in a hydrophilic solvent and injecting the monomers to synthesize these monomers into the polymer chain. As another method, a method of modifying particles by attaching a functional group containing a double bond to the surface of a particle and synthesizing a polymer on the surface using these functional groups has been utilized. The problem of the above two technologies is that it is difficult to include the microparticles in the polymer at high integration density, and also to control the size of the entire composite particles because the microparticles are randomly included in the polymer as the polymer is synthesized.

In more detail, when the fine particles are dispersed in a hydrophilic solvent and synthesized, fine control is performed because a large difference occurs in the number density contained in the polymer matrix of the internal fine particles according to the experimental conditions (synthesis temperature, mixing speed, type of solvent). It is difficult, and the method using the surface functional group also has the disadvantage that the number of particles contained in the polymer is very low and the size of the polymer is also impossible to control because the polymer is synthesized from the surface of the particle.

As described above, existing techniques for forming composite particles by dispersing inorganic fine particles in a polymer matrix have limitations in controlling the number density of internal fine particles.

In order to overcome this problem, in the present invention, by controlling the number density of the inorganic fine particles contained in the polymer matrix and the size of the total composite particles finely, the physical and chemical properties of the resulting core-shell structured composite particles of inorganic fine particles-carbon composition You can control the characteristics.

According to one or more exemplary embodiments, a method of preparing a core-shell structure including inorganic fine particles and carbon may include preparing hydrophilic inorganic fine particles; Surface-modifying the hydrophilic inorganic fine particles to make them hydrophobic; Dispersing the hydrophobic surface-modified inorganic fine particles in an organic solvent; Mixing and emulsifying water in the organic solvent; Mixing the polymer monomer in water and emulsifying; Polymerizing the polymer through a polymerization reaction after hybridization of the solution including the polymer monomer with the organic solvent; Coating a carbonizable polymer on the surface of the polymer including the inorganic fine particles to form a core-shell structure of the internal polymer and the carbonizable polymer including the inorganic fine particles; And pyrolyzing the internal polymer through high temperature heat treatment, and carbonizing the carbonizable polymer.

The hydrophilic inorganic fine particles are silicon-based fine particles. The silicon-based fine particles include any one or more of a silicon oxide of Si, SiOx, Si-Y (Y = Ge, Sn, Pb, Cu, Fe, Co, Ni, Mg, Zn, Ag, Al) alloy.

Mixing and emulsifying water in the organic solvent is performed by sonication after mixing the organic solvent with water containing a surfactant.

The polymer is preferably at least one of PS (Polystyrene), PMMA (Poly (methyl methacrylate), PVC (Polyvinyl chloride), PVF (Polyvinyl fluoride), PVA (Polyvinyl acetate), Polyacrylate-based polymer.

The carbonizable polymer is preferably one or more of dopamine, polypyrrole, polyacrylonitrile, polyaniline, and polythiene.

In the step of dispersing the hydrophobic surface-modified inorganic fine particles in the organic solvent, the weight ratio of the inorganic fine particles dispersed in the organic solvent is preferably 10wt% or less.

In the core-shell structure including inorganic fine particles and carbon according to an embodiment of the present invention, a plurality of inorganic fine particles are contained in the carbon shell, the water density of the inorganic fine particles is controlled, and the uniformity of the size is improved. . Such a structure can be used as a negative electrode material for a secondary battery.

The physicochemical performance of the core-shell structured composite material including inorganic fine particles and carbon is greatly changed by the uniformity of the number density and size of the inorganic fine particles contained therein. Therefore, it is necessary to develop a multi-particle material capable of high integration of internal particles while having high uniformity.

The present invention forms a core-shell structured particle of a silicon-carbon composition from a composite particle including a plurality of silicon fine particles in a polymer matrix, thereby solving the problem of low initial efficiency of a conventional silicon electrode material, while maintaining stable life characteristics. And developed a new electrode material for the negative electrode having a high initial efficiency characteristics.

In addition to the present embodiment, it is expected that the present invention may be utilized in various fields such as next-generation secondary battery materials and functional organic / inorganic composite structure coating materials by diversifying the type of inorganic fine particles contained therein and the polymer base material surrounding the outside.

1 shows a flow chart of a method for producing a core-shell structure comprising inorganic particulates and carbon according to one embodiment of the invention.
Figure 2 shows a schematic diagram of a method for producing a core-shell structure containing inorganic fine particles and carbon according to an embodiment of the present invention.
3 is a transmission electron micrograph (left column 1) and a scanning electron micrograph (right column 1) of a polymer including silicon particles synthesized through organic / inorganic hybrid polymerization, and the top photo is a octane-silicon of silicon / octane emulsion When the weight ratio is 6wt%, the lower picture shows a picture when 3wt%.
4 shows a transmission electron micrograph of a clustered silicon structure synthesized by heat treatment after coating dopamine on a polymer including silicon fine particles. Also, the photo on the right side shows a high magnification photo of the red box on the left side.
5 shows a graph between voltage and capacity prepared in the examples.
6 shows the life characteristics over the cycle of a sample.
7 shows the results of the initial efficiency analysis of the sample.
8 shows the cyclic voltammetry analysis results for the samples.
Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, various descriptions are set forth in order to provide an understanding of the present invention. It is evident, however, that such embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the embodiments.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific form disclosed, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, step, operation, component, part, or combination thereof described on the specification, but one or more other features or steps. It is to be understood that the present invention does not exclude in advance the possibility of the presence or the addition of an operation, a component, a part, or a combination thereof.

In the present invention, by utilizing the technology of trapping a plurality of silicon particles inside the polymer base material, it can solve the low initial efficiency problems due to the large surface area of the core-shell structure of the existing single silicon particle-carbon composition, while showing a stable life characteristics To fabricate a silicon-carbon composite particle material. In particular, the proposed technology can easily control the density of the inorganic fine particles contained in the polymer base material, and can be utilized as a high-performance secondary battery electrode material because high density integration is possible.

In the synthesis process, a polymer composite particle including a plurality of silicon fine particles is manufactured, and then a post-treatment is performed to produce a silicon-carbon core-shell composite structure including a plurality of silicon fine particles in one carbon layer, thereby providing high initial efficiency and It is possible to synthesize an electrode material having a stable life characteristics. First of all, by densifying the silicon fine particles in the polymer, as a result, the surface area of the whole particles can be lowered, leading to a result of improving the initial efficiency when using the electrode. In addition, it is possible to control the life characteristics of the electrode material by controlling the size of the silicon-carbon core-shell composite particles.

1 shows a flow chart of a method of manufacturing a core-shell structure comprising inorganic particulates and carbon according to one embodiment of the invention.

According to one or more exemplary embodiments, a method of preparing a core-shell structure including inorganic fine particles and carbon may include preparing hydrophilic inorganic fine particles (S 110); Surface-modifying the hydrophilic inorganic fine particles to make hydrophobic (S 120); Dispersing the hydrophobic surface-modified inorganic fine particles in an organic solvent (S 130); Mixing water with the organic solvent to emulsify (S 140); Mixing the polymer monomer in water and emulsifying it (S 150); Polymerizing the polymer through a polymerization reaction after forming a mixture of the solution including the polymer monomer and the organic solvent (S 160); Coating a carbonizable polymer on the surface of the polymer including the inorganic fine particles to form a core-shell structure of the internal polymer and the carbonizable polymer including the inorganic fine particles (S 170); And thermally decomposing the internal polymer through high temperature heat treatment, and carbonizing the carbonizable polymer (S 180).

In step S 110, hydrophilic inorganic fine particles are prepared. As the hydrophilic inorganic fine particles, silicon-based fine particles are used, and the silicon-based fine particles are Si, SiOx silicon oxide, Si-Y (Y = Ge, Sn, Pb, Cu, Fe, Co, Ni, Mg, Zn, Ag, Al) alloys It includes any one or more.

In step S 120, the hydrophilic inorganic fine particles are surface-modified to make hydrophobic. It is treated with a solution containing hydrophobic groups for hydrophobic treatment. For example, OTMS (Octadecyltrimethoxysilane) solution may be used as a solution including a hydrophobic group, but is not limited thereto.

In step S 130, the hydrophobic surface-modified inorganic fine particles are dispersed in an organic solvent. For example, an octane solution may be used as the organic solvent, but is not limited thereto. In this case, the weight ratio of the inorganic fine particles dispersed in the organic solvent is preferably 10 wt% or less. If it exceeds 10wt%, it is because the dispersion itself of the inorganic fine particles in the organic solvent is not well made.

In step S 140, water is mixed and emulsified in the organic solvent prepared in step S 130. The organic solvent containing inorganic fine particles is mixed with water containing surfactant, and emulsification is performed by sonication.

In step S 150, the polymer monomer is mixed with water and emulsified. The polymer monomer is mixed with the surfactant-containing water and emulsified. The polymer is subjected to a polymerization step in step S 160. The polymer may be any one or more of polystyrene (PS), poly (methyl methacrylate), polyvinyl chloride (PVC), polyvinyl fluoride (PVF), polyvinyl acetate (PVA), and polyacrylate-based polymers.

In step S 160, the polymer is polymerized through a polymerization reaction after hybridization of a solution including a polymer monomer with an organic solvent. The solution prepared in step S 140 and the solution prepared in step S 150 are mixed, and a polymerization initiator is mixed to cause a polymerization reaction.

In step S 170, a carbonizable polymer is coated on the surface of the polymer including the inorganic fine particles to form a core-shell structure of the internal polymer and the carbonizable polymer including the inorganic fine particles. The carbonizable polymer may be any one or more of dopamine, polypyrrole, polyacrylonitrile, polyaniline, and polythiene. The carbonizable polymer surrounds the surface of the polymer containing the inorganic fine particles to form a core-shell structure.

In step S 180, the internal polymer is thermally decomposed through high temperature heat treatment, and the carbonizable polymer is carbonized. As a result, a core-shell structure including inorganic fine particles and carbon is finally obtained.

In the core-shell structure including the inorganic fine particles and carbon obtained by the method described above, a plurality of inorganic fine particles are contained inside the carbon shell. In this case, as described in the prior art and the problem to be solved, in the case of the present invention, the water density of the inorganic fine particles is controlled, and the uniformity of the size is improved. The control of water density solved the problem of low initial efficiency and showed stable life characteristics. That is, since the polymer is synthesized after coating a functional group including a double bond on the surface of the fine particles (after hydrophobic treatment), the present invention is differentiated in that the control of the number of fine particles in the polymer is possible.

Hereinafter, the contents of the present invention together with the specific examples will be described in detail.

Figure 2 shows a schematic diagram of a method for producing a core-shell structure containing inorganic fine particles and carbon according to an embodiment of the present invention.

An ethanol solution in which 40 nm silicon fine particles were dispersed and a chloroform solution in which OTMS (Octadecyltrimethoxysilane) was dispersed were mixed, and then reacted for 3 hours to treat the surface of the silicon fine particles to be hydrophobic.

Hydrophobically modified silicon fine particles were dispersed in octane solution, and the concentration was adjusted to 6 wt%, 3 wt%, and 1 wt% based on the weight of silicon relative to octane.

The octane solution containing the silicon fine particles was mixed with water containing 20 mg SDS (Sodium Dodecyl Sulfate) surfactant, and then emulsion formation was induced by using an ultrasonic disperser.

5 ml of styrene monomer was mixed in water containing 20 mg SDS surfactant and emulsified.

The two solutions prepared above were mixed with a KPS initiator and reacted at 80 ° C. for 10 hours.

The polymer containing the synthesized silicon microparticles was centrifuged, washed, and dried at 60 ° C. for 6 hours.

The dried powder was mixed in Tris buffer (225 ml, 10 mM, pH 9 conditions) and dispersed using an ultrasonic disperser and then reacted with 450 mg of dopamine precursor to coat the dopamine polymer on the surface.

The composite synthesized above was centrifuged and washed, dried at 60 ° C. for 6 hours, and then heat treated at 800 ° C. for 2 hours under argon gas.

Through transmission electron microscopy (TEM) analysis, a phase in which a plurality of silicon particles are present inside the polymer before heat treatment, and after dopamine coating and heat treatment, contains silicon particles that are integrated at high density inside a single carbon layer shell It was confirmed that the core-shell structure was stably formed. 3 is a transmission electron micrograph (left column 1) and a scanning electron micrograph (right column 1) of a polymer containing silicon particles synthesized through organic / inorganic hybrid polymerization, and the top photo is a octane-silicon of silicon / octane emulsion When the weight ratio is 6wt%, the lower picture shows a picture when 3wt%.

4 shows a transmission electron micrograph of a clustered silicon structure synthesized by heat treatment after coating dopamine on a polymer including silicon fine particles. The photo at the top shows 6wt% and the photo at the bottom shows a 3wt% sample. Also, the photo on the right side shows a high magnification photo of the red box on the left side.

The coating thickness of the carbon layer using the dopamine was found to be very uniformly adjustable to the 10 ~ 15nm level.

Thereafter, the synthesized composite was prepared using a polyacrylic acid (PAlycrylic acid, PAA) binder and carbon black, and then coated on a copper substrate to prepare a negative electrode for a secondary battery.

Using a coin-type (CR 2032) battery, lithium metal was formed as a counter electrode (anode), and a battery performance test was conducted.

FIG. 5 shows a graph between voltage and capacity, and FIG. 6 shows lifetime characteristics over cycles. 7 shows the results of the initial efficiency analysis of the sample. 8 shows the cyclic voltammetry analysis results (CV) for the samples.

As a result of checking the battery performance, it was confirmed that as the number density of the silicon fine particles contained therein increases, the surface area of the entire composite particle decreases, thereby increasing initial efficiency. The resulting initial efficiency values were 80% for the weight ratio of silicon dispersed in octane, 75% for 3wt% and 71% for 1wt%.

Increasing the number of silicon fine particles contained therein increased the swelling / crushing action between the silicon fine particles, resulting in a decrease in lifespan characteristics.In the case of 3wt% samples, the capacity of reversible capacity up to 50 cycles was remarkable. It was confirmed that there was no decrease.

X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis showed that the SEI (Solid Electrolyte Interface) formation layer was stably maintained due to the structural stability of the silicon-carbon core-shell structure even when the battery-driven cycle was repeatedly performed. Confirmed.

The description of the presented embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention should not be limited to the embodiments set forth herein but should be construed in the broadest scope consistent with the principles and novel features set forth herein.

Claims (11)

Preparing hydrophilic inorganic fine particles;
Surface-modifying the hydrophilic inorganic fine particles to make them hydrophobic;
Dispersing the hydrophobic surface-modified inorganic fine particles in an organic solvent;
Mixing and emulsifying water in the organic solvent;
Mixing the polymer monomer in water and emulsifying;
Polymerizing the polymer through a polymerization reaction after hybridization of the solution including the polymer monomer with the organic solvent;
Coating a carbonizable polymer on the surface of the polymer including the inorganic fine particles to form a core-shell structure of the internal polymer and the carbonizable polymer including the inorganic fine particles; And
Pyrolysing the internal polymer through high temperature heat treatment, and carbonizing the carbonizable polymer,
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
The method of claim 1,
The hydrophilic inorganic fine particles are silicon-based fine particles,
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
The method of claim 2,
The silicon-based fine particles,
At least one of Si, SiOx silicon oxide, Si-Y (Y = Ge, Sn, Pb, Cu, Fe, Co, Ni, Mg, Zn, Ag, Al) alloy,
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
The method of claim 1,
Mixing and emulsifying water in the organic solvent,
By mixing the organic solvent with water containing a surfactant, followed by sonication,
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
The method of claim 1,
The polymer may be any one or more of polystyrene (PS), poly (methyl methacrylate), polyvinyl chloride (PVC), polyvinyl fluoride (PVF), polyvinyl acetate (PVA), and polyacrylate-based polymers.
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
The method of claim 1,
The carbonizable polymer,
At least one of dopamine, polypyrrole, polyacrylonitrile, polyaniline, and polythiene,
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
The method of claim 1,
Dispersing the hydrophobic surface-modified inorganic fine particles in an organic solvent,
The weight ratio of the inorganic fine particles dispersed in the organic solvent is 10wt% or less,
A method for producing a core-shell structure comprising inorganic fine particles and carbon.
Prepared according to the method of any one of claims 1 to 7,
Where a plurality of inorganic fine particles are contained within the carbon shell,
A core-shell structure comprising inorganic particulates and carbon.
The method of claim 8,
The water density of the inorganic fine particles is controlled, the size uniformity is improved,
A core-shell structure comprising inorganic particulates and carbon.
The method of claim 9,
The weight ratio of the inorganic fine particles dispersed in the organic solvent is 10wt% or less,
A core-shell structure comprising inorganic particulates and carbon.
A negative electrode material for a secondary battery, comprising a core-shell structure containing inorganic fine particles and carbon prepared according to any one of claims 1 to 7.

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