KR102544921B1 - Manufacturing method of siliconoxycarbide nano particle and manufacturing method of the secondary battery - Google Patents

Abstract

The present invention comprises the steps of dispersing or dissolving a silicon oxycarbide precursor containing an organosilicon monomer containing oxygen, silicon and carbon atoms in a solvent to form a precursor solution, and generating droplets from the precursor solution; The step of spraying the droplets into a preheated reactor, the step of reacting while the droplets are pyrolyzed in the reactor to produce silicon oxycarbide, the step of collecting particles that have passed through the reactor in a collector, and heat-treating the collected particles It relates to a method of manufacturing silicon oxycarbide nanoparticles and a method of manufacturing a secondary battery, including the step of carbonizing to obtain silicon oxycarbide nanoparticles. According to the present invention, mass production is possible using organosilicon monomers, and silicon oxycarbide having a spherical shape and a uniform particle size distribution can be produced.

Description

Manufacturing method of siliconoxycarbide nanoparticles and manufacturing method of the secondary battery using the same

The present invention relates to a method for manufacturing silicon oxycarbide nanoparticles and a method for manufacturing a secondary battery, and more particularly, to manufacture silicon oxycarbide that can be mass-produced using an organosilicon monomer and has a spherical shape and a uniform particle size distribution It relates to a method and a method of manufacturing a secondary battery using the same.

A lithium secondary battery is a secondary battery that is composed of a positive electrode and a negative electrode, a separator, and an electrolyte that generate electrical energy by a change in chemical potential during intercalation-deintercalation of lithium ions, and is capable of charging and discharging. . These lithium secondary batteries have high energy density, large electromotive force, and can exhibit high capacity, and thus are applied to various fields.

Carbonaceous materials such as artificial graphite, natural graphite, and amorphous carbon are mainly used as negative electrode active materials due to their excellent lifespan characteristics. However, since it has a relatively low theoretical capacity (∼372mAh g ^-1 ), many studies have been conducted on high-capacity negative electrode active materials to solve this problem.

Silicon (Si) has a high theoretical capacity (~3580mAh g ^-1 , Li ₁₅ Si ₄ ) and a low discharge potential (~0.4V vs. Li/Li ⁺ ), so it is a material that can replace existing carbon-based anode materials. is getting attention as However, since silicon is accompanied by a large volume change of 300% during the charge/discharge process, it causes the formation of unstable SEI (solid electrolyte interfaces) and pulverization of the electrode, resulting in loss of electrical contact and reduced capacity, making it difficult to commercialize. In order to solve this problem, various studies have been conducted, such as research on controlling silicon nanostructures through complex formation with carbon-based materials, but they still have problems such as low lifetime characteristics and high unit cost of the structure synthesis process.

Republic of Korea Patent Registration No. 10-1735456

The problem to be solved by the present invention is to provide a method for producing silicon oxycarbide that can be mass-produced using an organosilicon monomer, has a spherical shape and has a uniform particle size distribution, and a method for manufacturing a secondary battery using the same.

The present invention comprises the steps of (a) dispersing or dissolving a silicon oxycarbide precursor containing an organosilicon monomer containing oxygen, silicon and carbon atoms in a solvent to form a precursor solution, (b) removing droplets from the precursor solution. generating, (c) spraying the droplets into a preheated reactor, (d) reacting while the droplets are pyrolyzed in the reactor to produce silicon oxycarbide, (e) passing through the reactor It provides a method for producing silicon oxycarbide nanoparticles comprising the steps of collecting one particle in a collector and (f) heat-treating and carbonizing the collected particle to obtain silicon oxycarbide nanoparticles.

The organosilicon monomer is a chemical formula of R ¹ Si(OR ⁴ ) ₃ , R ¹ R ² Si(OR ⁴ ) ₂ and R ¹ R ² R ³ (OR ⁴ ) (where R ¹ is an aryl group or an alkenyl group, R ² , R ³ may be hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms), and R ⁴ may be hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms).

The silicon oxycarbide precursor is diphenylsilanediol, triphenylsilanol, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane and dimethyl It may include one or more materials selected from the group consisting of vinylsilanol (dimethylvinylsilanol).

The precursor solution may further include an acid catalyst to improve the reactivity of the silicon oxycarbide precursor.

The acid catalyst may include at least one material selected from the group consisting of sulfuric acid, chloric acid, and nitric acid.

The concentration of the precursor solution is preferably 0.1 to 5 M.

The size of the droplet is preferably 0.001 to 100 μm.

The temperature in the heated reactor is preferably 400 to 1200°C.

In the step (c), a carrier gas may be supplied so that the droplets are sprayed into the reactor, and the carrier gas is preferably supplied at a flow rate of 0.1 to 40 L/min.

The carbonization is preferably performed in an inert gas atmosphere.

The carbonization is preferably performed at a temperature of 600 to 1400 °C.

The silicon oxycarbide nanoparticles may have a spherical shape and have an average particle size of 50 to 300 nm.

The silicon oxycarbide nanoparticles may be formed in an amorphous phase.

In addition, the present invention, the silicon oxycarbide nanoparticles prepared by the manufacturing method of the silicon oxycarbide nanoparticles, 5 to 40 parts by weight of the conductive material based on 100 parts by weight of the silicon oxycarbide nanoparticles, 100 parts by weight of the silicon oxycarbide nanoparticles Preparing a composition for a negative electrode of a secondary battery by mixing 5 to 40 parts by weight of a binder and 200 to 1000 parts by weight of a dispersion medium with respect to 100 parts by weight of the silicon oxycarbide nanoparticles, and compressing the composition for a negative electrode of a secondary battery Formed in the form of an electrode, coated the composition for a negative electrode of a secondary battery on a metal foil or a current collector to form an electrode, or formed a sheet by pushing the composition for a negative electrode for a secondary battery with a roller and attached to a metal foil or a current collector to form an electrode Forming a negative electrode of a secondary battery by forming an electrode, or forming an electrode by casting it on a metal current collector by a doctor blade method, drying the result formed in the electrode shape, and intercalating or deintercalating lithium ions from the negative electrode Disposing a separator between the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode, and injecting an electrolyte in which lithium salt is dissolved between the positive electrode and the negative electrode. It provides a method for manufacturing a secondary battery comprising the step of doing.

According to the present invention, mass production is possible using organosilicon monomers, and silicon oxycarbide having a spherical shape and a uniform particle size distribution can be produced.

According to the present invention, it is possible to prepare nano-sized silicon oxycarbide particles having a uniform shape through a vapor phase synthesis method. Therefore, when used as an anode active material of a secondary battery, it is possible to reduce the diffusion distance of lithium ions during charging and discharging processes, so that rate capabilities can be improved.

Further, according to the present invention, the manufacturing process is simple, and mass production is possible through a continuous process.

1 is a schematic diagram of a vapor phase synthesis apparatus for producing silicon oxycarbide nanoparticles.
2 is a field emission scanning electron microscope (FE-SEM) photograph of silicon oxycarbide nanoparticles prepared according to Example 1.
3 is a field emission scanning electron microscope (FE-SEM) photograph of silicon oxycarbide nanoparticles prepared according to Example 2.
4 is a field emission scanning electron microscope (FE-SEM) photograph of silicon oxycarbide nanoparticles prepared according to Example 3.
5 is a field emission scanning electron microscope (FE-SEM) photograph of silicon oxycarbide nanoparticles prepared according to Example 4.
6 is a transmission electron microscope (TEM) analysis result of silicon oxycarbide prepared according to Example 4.
7 is an X-ray diffraction (XRD; X-ray Diffiraction) analysis result of silicon oxycarbide nanoparticles prepared according to Examples 1 to 4.
8 is a result of FT-IR (Fourier-Transform Infrared Spectroscopy) analysis of silicon oxycarbide nanoparticles prepared according to Examples 1 to 4.
9 is an XPS (X-ray Photoelectron Spectroscopy) analysis result of silicon oxycarbide nanoparticles prepared according to Example 4.
FIG. 10 is a graph showing a first potential profile in the range of 0.01 to 3V for a lithium secondary battery prepared using silicon oxycarbide nanoparticles prepared in Example 1 as an anode active material.
FIG. 11 is a graph showing a first potential profile in the range of 0.01 to 3V for a lithium secondary battery prepared using silicon oxycarbide nanoparticles prepared in Example 2 as an anode active material.
12 is a graph showing a first potential profile in the range of 0.01 to 3V for a lithium secondary battery prepared using silicon oxycarbide nanoparticles prepared in Example 3 as an anode active material.
14 is a graph showing a first potential profile in the range of 0.01 to 3V for a lithium secondary battery prepared using silicon oxycarbide nanoparticles prepared in Example 4 as an anode active material.
15 is a lithium secondary battery containing silicon oxycarbide nanoparticles prepared according to Examples 1 to 4 as an anode active material at 0.2, 0.5, 1, 2, 3, and 5A/V in the voltage range of 0.01-3V, respectively. This is a graph showing the rate performance when a current density of g is given.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to sufficiently understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the following examples. it is not going to be

When it is said that any one component "includes" another component in the detailed description or claims of the invention, it is not construed as being limited to only the corresponding component unless otherwise stated, and other components are not further defined. It should be understood that it can include.

Hereinafter, 'nano size' is a size in nanometers (nm) and is used to mean a size of 1 nm or more and less than 1 μm, and 'nanoparticles' means nano-sized particles. use.

Method for producing silicon oxycarbide nanoparticles according to a preferred embodiment of the present invention, (a) dispersing or dissolving a silicon oxycarbide precursor containing an organosilicon monomer containing oxygen, silicon and carbon atoms in a solvent to form a precursor solution Forming, (b) generating droplets from the precursor solution, (c) spraying the droplets into a preheated reactor, (d) reacting while the droplets are thermally decomposed in the reactor to form silicon oxide It includes generating carbide, (e) collecting the particles that have passed through the reactor in a collector, and (f) heat-treating and carbonizing the collected particles to obtain silicon oxycarbide nanoparticles.

The organosilicon monomer is a chemical formula of R ¹ Si(OR ⁴ ) ₃ , R ¹ R ² Si(OR ⁴ ) ₂ and R ¹ R ² R ³ (OR ⁴ ) (where R ¹ is an aryl group or an alkenyl group, R ² , R ³ may be hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms), and R ⁴ may be hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms).

The silicon oxycarbide precursor is diphenylsilanediol, triphenylsilanol, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane and dimethyl It may include one or more materials selected from the group consisting of vinylsilanol (dimethylvinylsilanol).

The precursor solution may further include an acid catalyst to improve the reactivity of the silicon oxycarbide precursor.

The acid catalyst may include at least one material selected from the group consisting of sulfuric acid, chloric acid, and nitric acid.

The concentration of the precursor solution is preferably 0.1 to 5 M.

The size of the droplet is preferably 0.001 to 100 μm.

The temperature in the heated reactor is preferably 400 to 1200°C.

In the step (c), a carrier gas may be supplied so that the droplets are sprayed into the reactor, and the carrier gas is preferably supplied at a flow rate of 0.1 to 40 L/min.

The carbonization is preferably performed in an inert gas atmosphere.

The carbonization is preferably performed at a temperature of 600 to 1400 °C.

The silicon oxycarbide nanoparticles may have a spherical shape and have an average particle size of 50 to 300 nm.

The silicon oxycarbide nanoparticles may be formed in an amorphous phase.

In the method for manufacturing a secondary battery according to a preferred embodiment of the present invention, the silicon oxycarbide nanoparticles prepared by the manufacturing method of the silicon oxycarbide nanoparticles and the silicon oxycarbide nanoparticles 5 to 40 parts by weight of the conductive material relative to 100 parts by weight Part, preparing a composition for a negative electrode for a secondary battery by mixing 5 to 40 parts by weight of a binder and 200 to 1000 parts by weight of a dispersion medium with respect to 100 parts by weight of the silicon oxycarbide nanoparticles based on 100 parts by weight of the silicon oxycarbide nanoparticles; The composition for a negative electrode of a secondary battery is compressed to form an electrode, or the composition for a negative electrode of a secondary battery is coated on a metal foil or a current collector to form an electrode, or the composition for a negative electrode of a secondary battery is pushed with a roller to form a sheet. Forming an electrode by attaching it to a metal foil or a current collector, or casting it on a metal current collector by a doctor blade method to form an electrode, drying the result formed in the form of an electrode to form a negative electrode of a secondary battery; Disposing a negative electrode, a positive electrode including a positive electrode active material capable of intercalating or deintercalating lithium ions, and a separator between the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode, and between the positive electrode and the negative electrode and injecting an electrolyte solution in which a lithium salt is dissolved.

Hereinafter, a method for manufacturing silicon oxycarbide nanoparticles according to a preferred embodiment of the present invention will be described in more detail.

Ceramics made from silicon-based polymers such as silicon oxycarbide have high lithium ion storage capacity, low expansion coefficient and mechanical stability. There are studies to use SiOC as an anode active material for lithium secondary batteries, but there is a problem with relatively low rate performance. This is because most silicon oxycarbide ceramics have large particle sizes and non-uniform shapes, which increases the diffusion distance of lithium ions during charge/discharge. Therefore, it is necessary to develop a synthesis technology having nano-sized particles that can be mass-produced relatively easily through a low-cost process.

1 is a schematic diagram of a vapor phase synthesis apparatus for producing silicon oxycarbide nanoparticles.

Referring to FIG. 1, a precursor solution is formed by dispersing or dissolving a silicon oxycarbide precursor including an organosilicon monomer containing oxygen, silicon, and carbon atoms in a solvent.

The organosilicon monomer is a chemical formula of R ¹ Si(OR ⁴ ) ₃ , R ¹ R ² Si(OR ⁴ ) ₂ and R ¹ R ² R ³ (OR ⁴ ) (where R ¹ is an aryl group or an alkenyl group, R ² , R ³ may be hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms), and R ⁴ may be hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms). The aryl group or alkenyl group serves as the main carbon source of silicon oxycarbide and improves the electrical conductivity of silicon oxycarbide. For example, triethoxyphenylsilane has a high O/Si ratio because three oxygen atoms and one phenyl group are bonded to silicon, which can lower the synthesis temperature, forming a nano-silica domain that can act as a buffer. At the same time, it is possible to form free carbon capable of increasing electrical conductivity.

An excellent carbon network can be formed at a relatively low temperature by selecting a precursor having an aryl group or an alkenyl group that is easy to form free carbon. Since the carbon network has good electrical conductivity, excellent reversibility and rate performance during charging and discharging can be obtained through the carbon network.

Low-viscosity silicon oxycarbide nanoparticles can be formed using an organosilicon monomer having a relatively high O/Si ratio compared to C/Si ratio, which can be heat treated at a low carbonization temperature. Therefore, at a high temperature, a part of the silicon oxycarbide network is decomposed into nano-sized silica domains and silicon carbide, so that high reversible capacity and excellent cycle retention can be obtained.

Since the organosilicon monomer is a monomer having a low molecular weight and a low vaporization point, nanoparticles can be easily formed through a vapor phase reaction when the precursor solution is sprayed through a droplet generating device.

The silicon oxycarbide precursor is diphenylsilanediol, triphenylsilanol, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane and dimethyl It may include one or more materials selected from the group consisting of vinylsilanol (dimethylvinylsilanol), but is not limited thereto.

The concentration of the precursor solution is preferably about 0.1 to 5 M, more preferably about 0.1 to 1 M. If the concentration of the precursor solution is too high, it may be difficult to disperse or dissolve the silicon oxycarbide precursor in a solvent, and it is difficult to generate droplets when applied to a vapor phase synthesis (more specifically, spray pyrolysis) process. Silicon oxycarbide nanoparticles There may be a limit to sufficiently recovering.

The solvent may be water, ethanol, methanol, or a mixture thereof, but is not limited thereto.

When forming the precursor solution, ultrasound may be applied to improve the degree of dispersion or dissolution of the silicon oxycarbide precursor, and the ultrasound may be performed for about 10 minutes to 1 hour, but is not limited thereto.

The precursor solution may further include an acid catalyst to improve the reactivity of the silicon oxycarbide precursor. The acid catalyst may include at least one material selected from the group consisting of sulfuric acid, chloric acid, and nitric acid, but is not limited thereto.

Droplets are generated from the precursor solution. The droplet may be generated through a droplet generator. The droplet generating device may be an ultrasonic spray device, an air nozzle spray device, an ultrasonic nozzle device, a filter expansion aerosol generator (FEAG), an electrostatic spray device, and the like. The size of the droplet greatly affects the size of the silicon oxycarbide nanoparticles to be produced. Therefore, the size of the droplet is preferably controlled to about 0.001 to 100 μm.

The droplets are atomized into a previously heated reactor (eg, furnace). The droplets may be moved to the reactor using a carrier gas. The carrier gas is preferably an inert gas such as argon (Ar) or nitrogen (N ₂ ), a reducing gas such as hydrogen (H ₂ ), or a mixed gas of an inert gas and a reducing gas, depending on the reaction system.

In the reactor, the liquid droplet reacts while being thermally decomposed, and silicon oxycarbide is produced. While the precursor solution in the form of droplets is thermally decomposed in the reactor, silicon oxycarbide is formed. The formation of the nanoparticles can be largely divided into first and second steps. In the first step, non-aggregated primary nanoparticles grow as the reaction proceeds, and in the second step, the primary nanoparticles are aggregated Secondary nanoparticles are formed. At this time, in order to convert into nano-sized silicon oxycarbide particles through gas phase synthesis, controlling the residence time of the droplets in the reactor and controlling the temperature of the reactor act as important factors. The liquid droplets sprayed into the reactor are pyrolyzed and reacted, and the precursor in a liquid state has a spherical shape to lower the degree of freedom, and nano-sized silicon oxycarbide particles are synthesized without the need for additional milling and classification processes.

The reaction time in the reactor may be controlled through the flow rate of the carrier gas. The residence time in the reactor is preferably controlled to 1 to 60 seconds depending on the size of the droplets and the reaction rate of the reactants. it is desirable If the flow rate of the carrier gas is too low, liquid droplet transport may not be smooth, resulting in a lower process yield. If the flow rate of the carrier gas is too high, the residence time in the reactor may be reduced, resulting in poor phase formation.

The temperature in the reactor is preferably about 400 to 1200 ° C. as an environment in which the precursor can be sufficiently vaporized. The atmosphere in the reactor is preferably an inert gas atmosphere (eg, argon (Ar) or nitrogen (N ₂ ) atmosphere), a reducing gas atmosphere (eg, hydrogen (H ₂ ) atmosphere), or a mixed gas atmosphere of an inert gas and a reducing gas. do. Preferably, the reactor is made of a heat-resistant ceramic material such as glass or alumina.

Particles passing through the reactor are collected in a collector (particle recovery device). The collector may be a recovery device using a bag filter, a recovery device using a cylindrical filter, or a recovery device using a cyclone.

By synthesizing silicon oxycarbide nanoparticles using a vapor phase synthesis (partial thermal decomposition) process, a grinding process that causes defects in the characteristics of the particles is not required, the manufacturing process is unified, and process time and cost can be saved. Silicon oxycarbide nanoparticles having a uniform size and spherical particles can be prepared by synthesizing a silicon oxycarbide precursor through a vapor phase synthesis (spray pyrolysis) process, and continuous production is possible by this method.

The synthesized silicon oxycarbide nanoparticles are carbonized by heat treatment. The carbonization is a process of making a silicon oxycarbide polymer into a ceramic. The carbonization is preferably performed in an inert gas atmosphere (eg, argon (Ar) or nitrogen (N ₂ ) atmosphere), a reducing gas atmosphere (eg, hydrogen (H ₂ ) atmosphere), or a mixed gas atmosphere of an inert gas and a reducing gas. However, it is not limited thereto. The carbonization is preferably performed at a temperature of about 600 ° C to 1400 ° C.

The silicon oxycarbide nanoparticles thus prepared may have a spherical shape and have an average particle size of 50 to 300 nm. The silicon oxycarbide nanoparticles may be formed in an amorphous phase.

Hereinafter, a method for manufacturing a secondary battery (eg, a lithium secondary battery) using silicon oxycarbide nanoparticles as an anode active material will be described in detail.

A composition for a negative electrode of a secondary battery is formed by mixing the silicon oxycarbide nanoparticles (negative electrode active material) prepared as described above, a conductive material, a binder, and a dispersion medium.

The conductive material is not particularly limited as long as it is an electron conductive material that does not cause chemical change, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, Super-P black, carbon fiber, copper, and nickel. , aluminum, metal powder or metal fibers such as silver, etc. are possible. The conductive material is preferably mixed in an amount of 5 to 40 parts by weight based on 100 parts by weight of the negative electrode active material.

As the dispersion medium, organic solvents such as ethanol (EtOH), acetone, isopropyl alcohol, N-methylpyrrolidone (NMP), and propylene glycol (PG) or water may be used. It is preferable to mix 200 to 1000 parts by weight of the dispersion medium based on 100 parts by weight of the negative electrode active material.

The binder is polytetrafluoroethylene (PTFE), polyvinylidenefloride (PVDF), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyvinyl butyral (polyvinyl alcohol). vinyl butyral (PVB), polyvinyl pyrrolidone (PVP), styrene butadiene rubber (SBR), polyamide-imide, polyimide or mixtures thereof, etc. can be used. The binder is preferably mixed in an amount of 5 to 40 parts by weight based on 100 parts by weight of the negative electrode active material.

A slurry suitable for manufacturing an electrode (negative electrode) can be obtained by stirring for a predetermined time (eg, 1 minute to 24 hours) using a high-speed mixer to uniformly disperse the negative electrode active material and the conductive material. The stirring is preferably performed at a rotational speed of about 100 to 4,000 rpm.

The composition for a negative electrode of a secondary battery thus prepared is in a slurry state.

A composition for a negative electrode for a secondary battery in which a negative electrode active material, a binder, a conductive material, and a dispersion medium are mixed is compressed to form an electrode, or the composition for a negative electrode for a secondary battery is coated on a metal foil or a current collector to form an electrode, or the composition for a negative electrode for a secondary battery is formed in the form of an electrode. The negative electrode composition is pushed with a roller to form a sheet, attached to a metal foil or a current collector to form an electrode, and the result formed in the form of an electrode is dried at a temperature of 100 ° C to 350 ° C to form a negative electrode of a secondary battery . A negative electrode may be formed using a metal (alloy) current collector. It may be dried to form a negative electrode of a secondary battery.

To describe an example of forming a negative electrode of a secondary battery in more detail, the composition for a negative electrode of a secondary battery may be compressed and molded using a roll press molding machine. The purpose of the roll press molding machine is to improve electrode density and control the thickness of electrodes through rolling. consists of parts As the rolled electrode passes through the roll press, the rolling process proceeds, and it is wound into a roll again. At this time, the pressing pressure of the press is preferably 5 to 20 ton/cm 2 and the temperature of the roll is 0 to 150° C. The composition for a negative electrode of a secondary battery that has undergone the press pressing process as described above is subjected to a drying process. The drying process is performed at a temperature of 100°C to 350°C, preferably 150°C to 300°C. At this time, when the drying temperature is less than 100 ° C., it is difficult to evaporate the dispersion medium, which is not preferable, and when drying at a high temperature exceeding 350 ° C., oxidation of the conductive material may occur. Therefore, the drying temperature is preferably 100°C or higher and does not exceed 350°C. And, it is preferable to proceed with the drying process for about 10 minutes to 6 hours at the same temperature as above. In this drying process, the molded secondary battery negative electrode composition is dried (dispersion medium evaporation) and at the same time the powder particles are bound to improve the strength of the secondary battery negative electrode.

In addition, looking at another example of forming the negative electrode of a secondary battery, the composition for the secondary battery negative electrode is titanium foil (Ti foil), aluminum foil (Al foil), aluminum etching foil (Al etching foil), copper foil (Cu foil) It may be coated on a metal foil such as, or the composition for a negative electrode of a secondary battery may be pushed with a roller to form a sheet (rubber type) and attached to a metal foil to form a negative electrode. The aluminum etching foil means an aluminum foil etched into a concave-convex shape. A drying process is performed on the cathode shape that has undergone the above process. The drying process is performed at a temperature of 100°C to 350°C, preferably 150°C to 300°C. At this time, when the drying temperature is less than 100 ° C., it is difficult to evaporate the dispersion medium, which is not preferable, and when drying at a high temperature exceeding 350 ° C., oxidation of the conductive material may occur. Therefore, the drying temperature is preferably 100°C or higher and does not exceed 350°C. And, it is preferable to proceed with the drying process for about 10 minutes to 6 hours at the same temperature as above. In this drying process, the composition for a negative electrode of a secondary battery is dried (evaporation of the dispersion medium) and at the same time, the strength of the negative electrode of the secondary battery is improved by binding the powder particles.

The secondary battery negative electrode manufactured as described above can be usefully applied to a desired type of secondary battery such as a coin cell.

As described above, a negative electrode manufactured using the negative electrode active material, a positive electrode including a positive electrode active material capable of intercalating or deintercalating lithium ions, and a separator between the positive electrode and the negative electrode to prevent short circuit between the positive electrode and the negative electrode ( A secondary battery may be manufactured by disposing a separator) and injecting an electrolyte solution in which lithium salt is dissolved between the positive electrode and the negative electrode.

The positive electrode may include at least one positive electrode active material selected from lithium metal, lithium alloy, crystalline carbon, amorphous carbon, carbon composite, and carbon fiber, but is not limited thereto. The cathode may also be manufactured by the same or similar method as the method of manufacturing the anode.

The separator is a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyester nonwoven fabric, a polyacrylonitrile porous separator, a poly(vinylidene fluoride) hexafluoropropane copolymer porous separator, a cellulose porous separator, kraft paper or rayon fiber, etc. It is not particularly limited as long as it is a generally used separator.

An electrolyte in which a lithium salt is dissolved may be used as an electrolyte of an electrolyte solution charged in a secondary battery. The lithium salt is not particularly limited as a lithium salt commonly used in secondary batteries, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , Li(CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ , LiAsF ₆ or mixtures thereof. The lithium salt is preferably contained in the electrolyte solution at a concentration of 0.1 to 3M.

The solvent constituting the electrolyte is not particularly limited, and examples thereof include cyclic carbonate solvents, chain carbonate solvents, ester solvents, ether solvents, nitrile solvents, amide solvents, or mixtures thereof. . As the cyclic carbonate-based solvent, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, etc. may be used, and as the chain carbonate-based solvent, dimethyl carbonate, methylethyl carbonate, diethyl carbonate, etc. may be used. As the ester solvent, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, etc. may be used, and as the ether solvent, 1,2-dimethoxyethane, 1,2-die Toxyethane, tetrahydrofuran, 1,2-dioxane, 2-methyltetrahydrofuran, etc. may be used, and acetonitrile may be used as the nitrile solvent, and dimethylformamide may be used as the amide solvent. can be used.

Hereinafter, experimental examples according to the present invention are specifically presented, and the present invention is not limited by the experimental examples presented below.

<Example 1>

Triethoxyphenylsilane was prepared as a precursor. 0.5 M of the triethoxyphenylsilane was mixed with 200 ml of ethanol and stirred to prepare a uniform precursor solution.

Using a peristaltic pump, the precursor solution was injected at a flow rate of 0.5 ml/min into an ultrasonic nozzle, which is a droplet generator, and droplets were generated through the ultrasonic nozzle. The droplets were sprayed into a previously heated reactor (heating furnace), and the droplets were moved into the reactor using a carrier gas. In the reactor, the liquid droplet reacts while being thermally decomposed, and silicon oxycarbide is produced. Argon (Ar) was used as a carrier gas and was injected at a flow rate of 10 L/min. The temperature of the reactor was set to 900 °C.

Particles passing through the reactor were collected in a collector (particle collection unit).

The collected particles were carbonized by heat treatment in an argon gas atmosphere to obtain silicon oxycarbide nanoparticles. The heat treatment was performed at 700° C. for 2 hours, and the flow rate of argon gas was 2 L/min.

<Example 2>

Triethoxyphenylsilane was prepared as a precursor. 0.5 M of the triethoxyphenylsilane was mixed with 200 ml of ethanol and stirred to prepare a uniform precursor solution.

Using a peristaltic pump, the precursor solution was injected at a flow rate of 0.5 ml/min into an ultrasonic nozzle, which is a droplet generator, and droplets were generated through the ultrasonic nozzle. The droplets were sprayed into a previously heated reactor (heating furnace), and the droplets were moved into the reactor using a carrier gas. In the reactor, the liquid droplet reacts while being thermally decomposed, and silicon oxycarbide is produced. Argon (Ar) was used as a carrier gas and was injected at a flow rate of 10 L/min. The temperature of the reactor was set to 900 °C.

Particles passing through the reactor were collected in a collector (particle collection unit).

The collected particles were carbonized by heat treatment in an argon gas atmosphere to obtain silicon oxycarbide nanoparticles. The heat treatment was performed at 900° C. for 2 hours, and the flow rate of argon gas was 2 L/min.

<Example 3>

Triethoxyphenylsilane was prepared as a precursor. 0.5 M of the triethoxyphenylsilane was mixed with 200 ml of ethanol and stirred to prepare a uniform precursor solution.

Using a peristaltic pump, the precursor solution was injected at a flow rate of 0.5 ml/min into an ultrasonic nozzle, which is a droplet generator, and droplets were generated through the ultrasonic nozzle. The droplets were sprayed into a previously heated reactor (heating furnace), and the droplets were moved into the reactor using a carrier gas. In the reactor, the liquid droplet reacts while being thermally decomposed, and silicon oxycarbide is produced. Argon (Ar) was used as a carrier gas and was injected at a flow rate of 10 L/min. The temperature of the reactor was set to 900 °C.

Particles passing through the reactor were collected in a collector (particle collection unit).

The collected particles were carbonized by heat treatment in an argon gas atmosphere to obtain silicon oxycarbide nanoparticles. The heat treatment was performed at 1100° C. for 2 hours, and the flow rate of argon gas was 2 L/min.

<Example 4>

Triethoxyphenylsilane was prepared as a precursor. 0.5 M of the triethoxyphenylsilane was mixed with 200 ml of ethanol and stirred to prepare a uniform precursor solution.

Using a peristaltic pump, the precursor solution was injected at a flow rate of 0.5 ml/min into an ultrasonic nozzle, which is a droplet generator, and droplets were generated through the ultrasonic nozzle. The droplets were sprayed into a previously heated reactor (heating furnace), and the droplets were moved into the reactor using a carrier gas. In the reactor, the liquid droplet reacts while being thermally decomposed, and silicon oxycarbide is produced. Argon (Ar) was used as a carrier gas and was injected at a flow rate of 10 L/min. The temperature of the reactor was set to 900 °C.

Particles passing through the reactor were collected in a collector (particle collection unit).

The collected particles were carbonized by heat treatment in an argon gas atmosphere to obtain silicon oxycarbide nanoparticles. The heat treatment was performed at 1300° C. for 2 hours, and the flow rate of argon gas was 2 L/min.

2 is a Field Emission Scanning Electron Microscope (FE-SEM) photograph of silicon oxycarbide nanoparticles prepared in Example 1, and FIG. 3 is a silicon oxycarbide nanoparticle prepared in Example 2. A field emission scanning electron microscope (FE-SEM) photograph of, Figure 4 is a field emission scanning electron microscope (FE-SEM) photograph of silicon oxycarbide nanoparticles prepared according to Example 3, Figure 5 is in Example 4 This is a field emission scanning electron microscope (FE-SEM) picture of silicon oxycarbide nanoparticles prepared according to the method.

6 is a transmission electron microscope (TEM) analysis result of silicon oxycarbide prepared according to Example 4.

2 to 6, silicon oxycarbide nanoparticles have an average particle diameter of about 100 nm, indicating that silicon, oxygen, and carbon atoms are uniformly distributed.

7 is an X-ray diffraction (XRD; X-ray Diffiraction) analysis result of silicon oxycarbide nanoparticles prepared according to Examples 1 to 4. 7, (a) is for silicon oxycarbide nanoparticles prepared according to Example 1, (b) is for silicon oxycarbide nanoparticles prepared according to Example 2, and (c) is for Example 3 For silicon oxycarbide nanoparticles prepared according to, and (d) for silicon oxycarbide nanoparticles prepared according to Example 4.

Referring to FIG. 7 , it can be seen that a broad peak is observed at 2θ = 21 to 23 °, which coincides with the peak position of the amorphous silica domain. In particular, in the case of the silicon oxycarbide nanoparticles carbonized at 1300 ° C. according to Example 4, it is determined that the amorphous silica domain is generated due to phase separation at high temperature, considering that the peak intensity of the silica domain is large.

8 is a result of FT-IR (Fourier-Transform Infrared Spectroscopy) analysis of silicon oxycarbide nanoparticles prepared according to Examples 1 to 4. 8, (a) is for silicon oxycarbide nanoparticles prepared according to Example 1, (b) is for silicon oxycarbide nanoparticles prepared according to Example 2, and (c) is for Example 3 For silicon oxycarbide nanoparticles prepared according to, and (d) for silicon oxycarbide nanoparticles prepared according to Example 4.

Referring to FIG. 8, a silicon oxycarbide network, Si-O-Si, is observed near the 1070 cm ^-1 peak, and after carbonization at 1300 ° C, the peak moves to a high frequency region. This means that the carbon atoms are separated from the silicon oxycarbide network. In addition, it can be seen that the 785 cm ^-1 peak shifts to 883 cm ^-1 , which is due to the stretching vibration of the Si—C bond. Therefore, it can be seen that when the carbonization temperature is 1300° C. or more, a part of the silicon oxycarbide is phase separated to form a silica domain and silicon carbide.

9 is an XPS (X-ray Photoelectron Spectroscopy) analysis result of silicon oxycarbide nanoparticles prepared according to Example 4.

Referring to FIG. 9 , SiO ₄ groups representing silica and Si-O-Si bonds can be observed.

An electrode was prepared using the silicon oxycarbide nanoparticles prepared according to Examples 1 to 4 as an anode active material. More specifically, a slurry is formed by mixing silicon oxycarbide nanoparticles, super-P as a conductive material, and polyvinylidenefloride (PVDF) as a binder in a weight ratio of 7:2:1, A negative electrode was prepared by spreading and applying the slurry thinly on a copper foil.

An electrode prepared by using lithium metal as a counter electrode and using silicon oxycarbide nanoparticles prepared according to Examples 1 to 4 as an anode active material was used as an anode. Add 5wt% of fluoroethylene carbonate (FEC) to a mixed solution in which 1.0M LiPF6 is mixed with ethylene carbonate (EC) and diethylcarbonate (DEC) in a volume ratio of 1:1 was used as an electrolyte. A polyolefin separator was used as a separator between the negative electrode and the counter electrode. A 2032 cell was used, and a lithium secondary battery was manufactured by assembling in a dry room. Charge/discharge was performed in the range of 0.01 to 3V.

10 is a graph showing a potential distribution (first potential profile) in the 0.01 to 3V region for a lithium secondary battery prepared using silicon oxycarbide nanoparticles prepared according to Example 1 as an anode active material, and FIG. A graph showing the first potential profile in the range of 0.01 to 3V for a lithium secondary battery prepared using silicon oxycarbide nanoparticles prepared according to Example 2 as an anode active material, and FIG. 13 is a graph showing the first potential profile in the 0.01 to 3V region for a lithium secondary battery prepared using the prepared silicon oxycarbide nanoparticles as an anode active material, and FIG. It is a graph showing the first potential profile in the range of 0.01 to 3V for a lithium secondary battery manufactured using carbide nanoparticles as an anode active material.

Referring to FIGS. 10 to 13 , it can be observed that the higher the carbonization temperature, the higher the reversible capacity, and the higher the plateau potential around 0.4 to 0.45V when lithium is inserted. This is because a C=C bond was created and free carbon capable of reacting with lithium ions increased. In addition, when silicon oxycarbide nanoparticles carbonized at 1300 ° C. were used as an anode active material (when silicon oxycarbide nanoparticles prepared according to Example 4 were used as a cathode active material), the reversible capacity was slightly reduced, but as the cycle progressed, lithium desorption A plateau is formed around 0.5 to 1.0V. As a result, silicon oxycarbide is phase-separated at high temperature to form irreversible silicon carbide and silica domains, and silica forms amorphous silicon through repetitive charging and discharging processes, thereby exhibiting stable life characteristics without capacity reduction.

14 is a graph showing the CV (cyclic voltammogram) in the range of 0.01 to 3V for a lithium secondary battery including silicon oxycarbide nanoparticles prepared according to Example 4 as an anode active material.

Referring to FIG. 14, after 50 cycles, a peak according to lithium ion insertion/desorption into amorphous silicon is shown.

15 is a lithium secondary battery containing silicon oxycarbide nanoparticles prepared according to Examples 1 to 4 as an anode active material at 0.2, 0.5, 1, 2, 3, and 5A/V in the voltage range of 0.01-3V, respectively. This is a graph showing the rate performance when a current density of g is given. 15, (a) is for the case where silicon oxycarbide nanoparticles prepared according to Example 1 are used as an anode active material, and (b) is for the case where silicon oxycarbide nanoparticles prepared according to Example 2 are used as an anode active material. For the case, (c) is for the case of using the silicon oxycarbide nanoparticles prepared according to Example 3 as an anode active material, (d) is for the case where the silicon oxycarbide nanoparticles prepared according to Example 4 are used as the negative electrode active material This is for the case of using .

Referring to FIG. 15, when silicon oxycarbide nanoparticles carbonized at 1300 ° C. were used as an anode active material (when silicon oxycarbide nanoparticles prepared according to Example 4 were used as a cathode active material), even at a current density of 5 A / g, the most It shows stable rate performance, because the uniform and spherical nanoparticles can reduce the lithium diffusion distance, and the excellent chemical stability of silicon carbide suppresses the formation of an SEI layer on the surface of silicon.

In the above, the preferred embodiment of the present invention has been described in detail, but the present invention is not limited to the above embodiment, and various modifications are possible by those skilled in the art.

Claims (14)

(a) forming a precursor solution by dispersing or dissolving a silicon oxycarbide precursor containing an organosilicon monomer containing oxygen, silicon and carbon atoms in a solvent;
(b) generating droplets from the precursor solution;
(c) atomizing the droplets into a preheated reactor;
(d) generating silicon oxycarbide by reacting while the liquid droplets are thermally decomposed in the reactor;
(e) collecting particles passing through the reactor in a collector; and
(f) carbonizing the collected particles by heat treatment to obtain silicon oxycarbide nanoparticles,
The organosilicon monomer is a chemical formula of R ¹ Si(OR ⁴ ) ₃ , R ¹ R ² Si(OR ⁴ ) ₂ and R ¹ R ² R ³ (OR ⁴ ) (where R ¹ is an aryl group or an alkenyl group, R ² , R ³ is hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms), R ⁴ is hydrogen or alkyl (hydrocarbon having 1 to 5 carbon atoms),
The silicon oxycarbide precursor comprises at least one material selected from the group consisting of diphenylsilanediol, triphenylsilanol and dimethylvinylsilanol. Manufacturing method of.
delete delete The method of claim 1, wherein the precursor solution further comprises an acid catalyst to improve the reactivity of the silicon oxycarbide precursor.
The preparation of silicon oxycarbide nanoparticles according to claim 4, wherein the acid catalyst comprises at least one material selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid. method.
The method for producing silicon oxycarbide nanoparticles according to claim 1, wherein the concentration of the precursor solution is 0.1 to 5 M.
The method of claim 1, wherein the size of the droplet is 0.001 to 100 μm.
The method for producing silicon oxycarbide nanoparticles according to claim 1, wherein the temperature in the heated reactor is 400 to 1200 °C.
The method of claim 1, wherein step (c) supplies a carrier gas so that the droplets are sprayed into the reactor,
The carrier gas is a method for producing silicon oxycarbide nanoparticles, characterized in that supplied at a flow rate of 0.1 to 40 ℓ / min.
The method of claim 1, wherein the carbonization is performed in an inert gas atmosphere.
The method for producing silicon oxycarbide nanoparticles according to claim 1, wherein the carbonization is performed at a temperature of 600 to 1400 °C.
The method of claim 1, wherein the silicon oxycarbide nanoparticles have a spherical shape and have an average particle size of 50 to 300 nm.
The method of claim 1, wherein the silicon oxycarbide nanoparticles are made of an amorphous phase.
Silicon oxycarbide nanoparticles prepared by the method according to claim 1, 5 to 40 parts by weight of a conductive material based on 100 parts by weight of the silicon oxycarbide nanoparticles, and 5 to 40 parts by weight of a binder based on 100 parts by weight of the silicon oxycarbide nanoparticles preparing a composition for a negative electrode of a secondary battery by mixing 200 to 1000 parts by weight of a dispersion medium with respect to 100 parts by weight of the silicon oxycarbide nanoparticles;
The composition for a negative electrode of a secondary battery is compressed to form an electrode, or the composition for a negative electrode of a secondary battery is coated on a metal foil or a current collector to form an electrode, or the composition for a negative electrode of a secondary battery is pushed with a roller to form a sheet. Forming an electrode by attaching it to a metal foil or current collector, or forming an electrode by casting on a metal current collector using a doctor blade method;
drying the product formed in the form of an electrode to form a negative electrode of a secondary battery;
disposing a separator between the negative electrode, a positive electrode including a positive electrode active material capable of intercalating or deintercalating lithium ions, and a separator between the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode; and
A method of manufacturing a secondary battery comprising the step of injecting an electrolyte solution in which lithium salt is dissolved between the positive electrode and the negative electrode.

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