Negative electrode active material, negative electrode including same, and method for manufacturing negative electrode active material

Abstract

Provided, according to exemplary embodiments of the present invention, is a negative electrode active material capable of improving the efficiency of a secondary battery. The negative electrode active material comprises: a carbon scaffold having a porous structure; and silicon-based particles distributed in pores of the carbon scaffold, wherein the carbon scaffold comprises a plurality of carbon structures which are agglomerated with each other. Provided, according to other exemplary embodiments of the present invention, are a method for manufacturing the above-described negative electrode active material, and a negative electrode comprising the negative electrode active material.

Description

Negative active material, negative electrode comprising the same, and method for producing the negative active material

[0001] The present invention relates to a negative electrode active material and a negative electrode including the same.

[0002] In addition, the present invention relates to a method for manufacturing a negative electrode active material.

[0003] Recently, the rapid advancement of portable and wireless electronic devices has led to a growing demand for compact, lightweight, and high-energy-density secondary batteries as power sources for these devices. Furthermore, high-output characteristics, long-term durability, and safety are required not only for small consumer applications but also for large-scale secondary batteries used in power storage devices and electric vehicles.

[0004] A secondary battery has a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and an electrolyte are accommodated in an outer body. The electrode includes an electrode current collector and an electrode active material layer positioned on at least one side of the electrode current collector. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer positioned on at least one side of the positive electrode current collector. The negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on at least one side of the negative electrode current collector.

[0005] Secondary batteries can be categorized into lead-acid batteries, nickel-cadmium (Cd) batteries, nickel-metal hydride (MH) batteries, and lithium batteries, depending on the type of cathode and anode active materials. Among these, demand for lithium secondary batteries, with their superior energy density, output characteristics, and operating time, is growing.

[0006] The secondary battery reaction of a lithium secondary battery is carried out through a chemical reaction in which lithium ions (Li+) move between the positive electrode active material and the negative electrode active material.

[0007] In the field of secondary batteries, much research is ongoing on the efficiency related to the charge / discharge capacity of secondary batteries, as this is a characteristic directly related to the long-term performance of devices that use secondary batteries as a power source.

[0008] (Patent Document 1) Republic of Korea Patent Publication No. 10-1825919.

[0009] The technical idea of ​​the present invention aims to solve a problem by providing a negative electrode active material capable of improving the charge / discharge capacity and efficiency of a secondary battery and a negative electrode including the same.

[0010] Another problem that the technical idea of ​​the present invention seeks to solve is to provide a method for manufacturing the above-described negative electrode active material.

[0011] The objectives of the present invention are not limited to the above-described content. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall description of the present invention.

[0012] According to exemplary embodiments of the present invention, a negative electrode active material is provided. The negative electrode active material comprises: a carbon scaffold having a porous structure; and silicon-based particles distributed in the pores of the carbon scaffold; wherein the carbon scaffold comprises a plurality of carbon structures aggregated with each other.

[0013] The above carbon structure may be any one of a linear carbon structure, a planer carbon structure, a ball-shaped carbon structure, and a combination thereof.

[0014] The content of the above planar carbon structure may be higher than the content of the above linear carbon structure.

[0015] The linear carbon structure may include any one of carbon nanotubes, carbon nanofibers, and combinations thereof.

[0016] The above planar carbon structure may include graphene.

[0017] The D50 of the above negative active material may be 0.5 to 20.0 μm.

[0018] The D50 of the above negative active material may be 3 to 15 μm.

[0019] The specific surface area of ​​the above carbon scaffold is 300-500 m 2 / g may be.

[0020] The pore volume of the above carbon scaffold is 0.8 to 2.0 cm 2 / g may be.

[0021] The average pore size (width) of the above carbon scaffold may be 2 to 8 nm.

[0022] The above silicon particles may be characterized as being deposited in the pores of the carbon scaffold.

[0023] The carbon scaffold may further include a coating layer provided on the surface thereof.

[0024] According to other exemplary embodiments of the present invention, a method for manufacturing an anode active material is provided. The method for manufacturing the anode active material comprises the steps of: preparing a carbon slurry in which a carbon structure is dispersed in a solvent; spray drying the carbon slurry to obtain a carbon scaffold having a porous structure; and providing silicon to the carbon scaffold.

[0025] The step of providing the above silicon can be performed by depositing a silicon-based precursor fluid into the pores of the carbon scaffold at 400 to 900°C.

[0026] The above carbon structure may be any one of a linear carbon structure, a planer carbon structure, a ball-shaped carbon structure, and a combination thereof.

[0027] The method for manufacturing the above negative active material may further include a step of providing a coating layer on the surface of the carbon scaffold after depositing the silicon-based precursor fluid.

[0028] According to further exemplary embodiments of the present invention, a negative electrode is provided. The negative electrode may include: a negative electrode current collector; and a negative electrode active material layer comprising the above-described negative electrode active material, the negative electrode active material layer being positioned on one or both surfaces of the negative electrode current collector.

[0029] The negative active material according to exemplary embodiments of the present invention can improve the efficiency of a negative electrode and a secondary battery including the negative active material by providing a negative active material including a carbon scaffold structure with improved initial efficiency.

[0030] According to further exemplary embodiments of the present invention, a secondary battery provides a method for manufacturing an anode active material capable of forming a carbon scaffold structure at relatively low temperatures. This can improve the manufacturing efficiency of the anode active material.

[0031] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0032] Figure 1 is a graph showing the efficiency of secondary batteries according to silicon content.

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0034] Hereinafter, when explaining with reference to drawings, identical or corresponding components are given the same drawing reference numerals and redundant descriptions thereof are omitted.

[0035] In the embodiments below, terms such as first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another.

[0036] In the following embodiments, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0037] In the embodiments below, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

[0038] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to what is shown.

[0039] If a particular embodiment is capable of being implemented differently, a particular process sequence may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0040] In addition, when describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description is omitted.

[0041]

[0042] In the present invention, having a micro-scale size refers to a particle size distribution based on D50. That is, it means a case where D50 is 1.0㎛ or more. Therefore, even if the D10 of a particle is less than 1.0㎛, if the D50 of the particle is 1.0㎛ or more, the particle can be interpreted as having a micro-scale size according to the present invention.

[0043] In the present invention, D50, D10, and D90 can be defined as particle sizes corresponding to 50%, 10%, and 90% of the volume accumulation amount, respectively, in the particle size distribution curve of the particles. The D50, D10, and D90 can be measured using, for example, a laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0044]

[0045] Hereinafter, the negative electrode and the negative electrode active material according to exemplary embodiments of the present invention will be specifically described.

[0046]

[0047] [cathode]

[0048] According to exemplary embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer.

[0049]

[0050] The negative electrode current collector is not particularly limited as long as it has high conductivity and does not induce chemical changes in the battery. As non-limiting examples, the negative electrode current collector may include one or more of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and an aluminum-cadmium alloy.

[0051] The thickness of the negative electrode current collector can be 3 to 500 μm.

[0052]

[0053] The negative electrode active material layer may be provided on one or both sides of the negative electrode current collector. The negative electrode active material layer may be obtained by coating and drying a negative electrode slurry containing a binder, a conductive material, and a negative electrode active material on the negative electrode current collector.

[0054]

[0055] According to exemplary embodiments, the binder may be included in an amount of 30% or less (including 0%) by weight.

[0056] A binder is a component that assists in bonding between the negative electrode active material and the current collector. As a non-limiting example, the negative electrode binder may include at least one selected from polyvinyl alcohol, carboxymethyl cellulose / styrene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or polypropylene.

[0057]

[0058] According to exemplary embodiments, the conductive material may be included in an amount of 30% or less (including 0%) by weight.

[0059] A conductive agent is a component for improving the conductivity of a negative electrode active material. As non-limiting examples, the conductive agent may include at least one selected from the group consisting of graphite such as carbon nanotubes, natural graphite, and artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0060]

[0061] [Cathode active material]

[0062] The negative active material can generate electrical energy through the insertion and de-insertion reactions of lithium ions during the charging and discharging process of a secondary battery.

[0063] According to exemplary embodiments, the D50 of the negative active material may be 0.5 to 20.0 μm. More specifically, the D50 of the negative active material may be 3 to 15 μm. The D50 of the negative active material may be 3 to 10 μm.

[0064] The negative active material may include a carbon scaffold with a porous structure and silicon-based particles.

[0065] A carbon scaffold with a porous structure may be a composite of multiple carbon structures.

[0066] Conventionally, carbon scaffolds formed by carbonizing polymers have been used. Alternatively, carbon scaffolds have been manufactured based on activated carbon heat-treated at very high temperatures. However, when carbonizing polymers, the carbonization rate of the polymer is only about 20-40% of the initial polymer weight, resulting in poor yields. Furthermore, because conventional carbon scaffolds inherently have poor initial capacity and efficiency, negative electrode active materials or anodes manufactured using them suffer from reduced initial capacity and efficiency.

[0067] However, the carbon scaffold according to exemplary embodiments of the present invention is provided in an aggregated form in which carbon structures are entangled or bonded with each other. This eliminates the need for a high-temperature heat treatment process, thereby reducing the energy required to manufacture the negative electrode active material. Furthermore, the carbon scaffold, in the form of aggregated carbon structures, exhibits excellent initial capacity and efficiency, thereby improving the initial capacity and efficiency of the negative electrode or negative electrode manufactured based on the scaffold.

[0068] According to exemplary embodiments, the carbon structure may be any one of a linear carbon structure, a planar carbon structure, a ball-shaped carbon structure, and a combination thereof. More specifically, the carbon structure may be any one or more of a linear carbon structure, a planar carbon structure, and a combination thereof.

[0069] The linear carbon structure may be a carbon nanotube, a carbon nanofiber, or a combination thereof. When aggregated, the linear carbon structure forms an intertwined structure, which can more strongly anchor the carbon scaffold structure. This can enhance the structural stability of the negative electrode active material.

[0070] Planar carbon structures may include graphene. Planar carbon structures can exhibit superior charge and discharge capacities. This can further improve the electrochemical efficiency of the carbon scaffold.

[0071] According to exemplary embodiments, the content of planar carbon structures in the carbon scaffold may be higher than that of linear carbon structures. More specifically, linear carbon structures may contribute to the structural stability of the carbon scaffold and are relatively cheaper than planar carbon structures. However, since the electrical properties of planar carbon structures are superior to those of linear carbon structures, the content of planar carbon structures may be higher than that of linear carbon structures in terms of the efficiency of the secondary battery.

[0072] The ball-shaped carbon structure may include fullerene.

[0073] According to exemplary embodiments, the specific surface area of ​​the carbon scaffold is 300 to 600 m 2 / g. If the specific surface area of ​​the carbon scaffold is excessively low, its own capacity may be reduced. More specifically, the capacity of the secondary battery may be reduced if the silicon particles do not properly bond with the carbon scaffold. However, if the specific surface area of ​​the carbon scaffold is excessively high, the specific surface area of ​​the negative active material increases, which may cause side reactions with the electrolyte during the charge / discharge process of the secondary battery. In this case, the cycle life characteristics of the secondary battery may be deteriorated.

[0074] According to exemplary embodiments, the pore volume of the carbon scaffold is 0.8 to 2.0 cm 2 / g. The average pore size (width) of the carbon scaffold can be 2–8 nm. If the pore volume and pore size of the carbon scaffold are excessively small, the charge storage capacity may be reduced. Furthermore, the capacity of the secondary battery may be reduced if the silicon particles are not properly bound to the carbon scaffold. However, if the pore volume and pore size of the carbon scaffold are excessively large, side reactions with the electrolyte may occur during the charge / discharge process of the secondary battery.

[0075] The specific surface area, pore volume, and average pore size of the carbon scaffold can be measured or calculated by techniques known in the art, but as non-limiting examples, can be measured or calculated by one or more of the BET method or the BJH method.

[0076] According to exemplary embodiments, the carbon scaffold may further include a coating layer provided on the surface. The coating layer may cover the carbon scaffold structure to prevent the multi-porous structure of the carbon scaffold from being exposed to the outside.

[0077] As a non-limiting example, the coating layer may include any one of carbon, an ion-conducting polymer, a ceramic, an organic compound, and combinations thereof.

[0078] More specifically, the carbon may be provided on the surface of the carbon scaffold using a coating layer precursor fluid comprising any one of coal pitch, petroleum pitch, coal tar, methane, propane, butane, cyclohexane, ethane, propylene, acetylene, and combinations thereof, by using a thermal decomposition method or a chemical vapor deposition method. The ion conducting polymer may include at least one of an oligomer of any one of polyaniline, polypyrrole, polythiophene, and combinations thereof; PEDOT-PSS; polyvinylidene fluoride (PVDF); and a rubber comprising any one of vinylene, fluoride, neoprene, urethane, silicone, styrene-butadiene, isoprene, and combinations thereof. The ceramic may include any one of alumina titania, zirconia, chromium oxide, carbide, nitride, boride, silicide, and combinations thereof. The organic compound may include any one of lignin, cellulose, chitosan, polysaccharides, lipids, and combinations thereof.

[0079]

[0080] Silicon particles can be distributed within the pores of a carbon scaffold. More specifically, the silicon particles can be deposited within the pores of the carbon scaffold. Therefore, the silicon particles can be stably incorporated into the pores of the carbon scaffold and not easily detach from the carbon scaffold. Furthermore, when deposited within the internal pores of the carbon scaffold by deposition, the silicon particles can contain a high content of high-capacity silicon, making it easier to improve the capacity of a secondary battery.

[0081] As a non-limiting example, the silicon-based particles may include amorphous silicon. Amorphous silicon exhibits lower volume expansion than crystalline silicon. Therefore, by depositing amorphous silicon into the pores of a carbon scaffold, the capacity of the secondary battery can be improved while also enhancing its cycle life. This can enhance the efficiency of the secondary battery.

[0082]

[0083] [Method for manufacturing negative active material]

[0084] A method for manufacturing a negative electrode active material may include the steps of preparing a carbon slurry, obtaining a carbon scaffold, and providing silicon. Furthermore, the method for manufacturing a negative electrode active material may further include the step of providing a coating layer on the surface of the carbon scaffold.

[0085]

[0086] The step of preparing a carbon slurry can be performed by dispersing a carbon structure in a solvent. That is, the carbon slurry can include a carbon structure.

[0087] The carbon structure may be any one of a linear carbon structure, a planar carbon structure, a spherical carbon structure, and a combination thereof. More specifically, the carbon structure may be any one of a linear carbon structure, a planar carbon structure, a spherical carbon structure, and a combination thereof.

[0088] The linear carbon structure may include any one of carbon nanotubes, carbon nanofibers, and combinations thereof. The planar carbon structure may include any one of graphene, graphite, and combinations thereof. The ball-shaped carbon structure may include fullerene.

[0089] The solvent may be any one of an organic solvent, water, one or more water-miscible solvents, and combinations thereof. As a non-limiting example, the organic solvent may be any one of ethanol, methanol, isopropanol, and combinations thereof.

[0090] A dispersant may be added to the solvent. According to exemplary embodiments, the dispersant may be any one of a cellulose-based, acrylic-based, styrene-based, fatty acid-based, ester wax-based, polyvinyl acrylic (PVA)-based, and combinations thereof.

[0091]

[0092] The step of obtaining a carbon scaffold can be performed by spray drying the carbon slurry described above. As a result, a carbon scaffold with a porous structure can be obtained.

[0093] As described above, conventional methods for obtaining carbon scaffolds involved carbonizing a carbon-containing polymer or using high-temperature heat-treated activated carbon. However, these methods not only resulted in poor capacity and efficiency of the resulting carbon scaffolds, but also resulted in excessively low carbon scaffold yields.

[0094] However, according to exemplary embodiments, the carbon scaffold can be provided by agglomerating carbon structures using a spray drying method, thereby increasing the yield of the carbon scaffold and improving production efficiency.

[0095] The spray drying method can be performed by spraying carbon slurry into the interior of a spray dryer to atomize particles, and providing hot air into the interior of the spray dryer to evaporate the solvent of the carbon slurry to obtain a dried powder.

[0096] According to exemplary embodiments, the inlet temperature of the spray dryer may be 60 to 150°C. If the inlet temperature of the spray dryer is lower than 60°C, the solvent may not sufficiently evaporate. Furthermore, the carbon scaffold particles may become entangled with each other, resulting in a very large particle size of the carbon scaffold. If the inlet temperature of the spray dryer exceeds 150°C, shape control of the carbon scaffold may be difficult. Furthermore, the carbon structures may not become entangled with each other but may be dispersed as individual particles, making it difficult to form a carbon scaffold structure.

[0097] According to exemplary embodiments, the internal temperature of the spray dryer can be 90 to 200°C.

[0098] According to exemplary embodiments, the outlet temperature of the spray dryer may be 70 to 180°C. The outlet temperature of the spray dryer may be lower than or equal to the internal temperature of the spray dryer. The outlet temperature of the spray dryer may be higher than or equal to the inlet temperature of the spray dryer.

[0099] If the outlet temperature of the spray dryer is excessively low, the solvent in the carbon slurry may not be sufficiently removed, making it difficult to control the particle size of the carbon scaffold. If the outlet temperature of the spray dryer is excessively high, the solvent in the carbon slurry may be removed excessively quickly during transport, which may block the inlet of the spray dryer.

[0100] The conveying speed of the carbon slurry may be 10 to 50 cc / min. As a non-limiting example, the spray dryer may be any one of nozzle type, disk type, or a combination thereof.

[0101]

[0102] The step of providing silicon can be performed by depositing a silicon precursor fluid into the pores of the carbon scaffold at a predetermined temperature.

[0103] The silicon precursor fluid is not particularly limited as long as it is a fluid that can be deposited on a carbon scaffold, including silicon. As a non-limiting example, the silicon precursor fluid may be any one of silane, disilane, trisilane, tetrasilane, chlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane, including an alkyl moiety, and combinations thereof. More specifically, the silane including an alkyl moiety may be any one of methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, methyldisilane, dimethyldisilane, trimethyldisilane, tetramethyldisilane, hexamethylsilane, and combinations thereof.

[0104] According to exemplary embodiments, the deposition of the silicon precursor fluid may be performed via chemical vapor deposition (CVD). More specifically, the deposition of the silicon precursor fluid may be performed via one or more of plasma enhanced chemical vapor deposition (PECVD), microwave-assisted chemical vapor deposition (Microwave-assisted CVD), and chemical vapor infiltration (CVI).

[0105] According to exemplary embodiments, the deposition of the silicon precursor fluid may be performed at a temperature ranging from 400°C to 900°C. If the deposition temperature is too low, the silicon precursor fluid may not adequately diffuse into the internal pores of the carbon scaffold. Furthermore, the silicon precursor fluid may be deposited in a precursor fluid state without decomposition. In this case, the efficiency of the secondary battery may be reduced. However, if the deposition temperature is excessively high, the silicon precursor fluid may be deposited on the carbon scaffold in the form of crystalline silicon rather than amorphous silicon. Furthermore, the deposited silicon particles may aggregate to form coarse particles. This may result in a decrease in the capacity of the secondary battery.

[0106]

[0107] The step of providing a coating layer on the surface of the carbon scaffold may be performed by performing any one of thermal decomposition, chemical vapor deposition, and a combination thereof to provide a coating layer on the surface of the carbon scaffold from a coating layer precursor.

[0108] As a non-limiting example, the coating layer precursor may include any one of a carbon precursor, an ion conducting precursor, a ceramic precursor, an organic compound precursor, and combinations thereof.

[0109] More specifically, the carbon precursor may include any one of coal pitch, petroleum pitch, coal tar, methane, propane, butane, cyclohexane, ethane, propylene, acetylene, and combinations thereof. The ion-conducting precursor may include any one or more of an oligomer of any one of polyaniline, polypyrrole, polythiophene, and combinations thereof; PEDOT-PSS; polyvinylidene fluoride (PVDF); and a rubber including any one of vinylene, fluoride, neoprene, urethane, silicone, styrene-butadiene, isoprene, and combinations thereof. The ceramic precursor may include any one of alumina titania, zirconia, chromium oxide, carbide, nitride, boride, silicide, and combinations thereof. The organic compound precursor may include any one of lignin, cellulose, chitosan, polysaccharides, lipids, and combinations thereof.

[0110] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0111]

[0112] (Example 1)

[0113] A carbon slurry was prepared by mixing carbon nanotubes and a dispersant in absolute ethanol. The dispersant was included in an amount of 10 parts by weight per 100 parts by weight of absolute ethanol. The carbon nanotubes were included in an amount of 10 parts by weight per 100 parts by weight of absolute ethanol. As a result, the carbon scaffold was substantially composed only of carbon nanotubes. Subsequently, the carbon slurry was spray-dried under conditions of an inlet temperature of 70°C, a carbon slurry feed rate of 20-30 cc / min, and an internal temperature of 120°C to obtain a carbon scaffold. At this time, a nozzle-type spray dryer was used as the spray dryer. Subsequently, silane gas was deposited into the pores of the carbon scaffold using a CVD method to obtain a negative electrode active material.

[0114]

[0115] (Example 2)

[0116] Carbon nanotubes and graphene were mixed in a solvent to prepare a carbon slurry. The carbon nanotube content of the carbon scaffold was controlled to be 80% by weight. The graphene content of the carbon scaffold was controlled to be 20% by weight. Other details were the same as in Example 1 described above, to obtain a negative electrode active material.

[0117]

[0118] (Example 3)

[0119] Carbon nanotubes and graphene were mixed in a solvent to prepare a carbon slurry. The carbon nanotube content of the carbon scaffold was controlled to be 50% by weight. The graphene content of the carbon scaffold was controlled to be 50% by weight. Other details were the same as in Example 1 described above, to obtain a negative electrode active material.

[0120]

[0121] (Example 4)

[0122] A carbon slurry was prepared by mixing graphene with a solvent. As a result, the carbon scaffold was essentially composed entirely of graphene. The negative electrode active material was obtained by performing all other steps identically to Example 1 described above.

[0123]

[0124] (Comparative Example 1)

[0125] 5 ml of resorcinol and 100 ml of formaldehyde were mixed, and the mixture was stirred for 15 minutes to obtain a homogeneous reaction mixture. Additionally, 0.9 ml of ammonium hydroxide and 50 ml of deionized water were added to the solution for gelation. The sol was maintained at 80°C for 2 hours for gelation. After gelation, the wet gel was immersed in acetone at 40°C for 5 hours to exchange the solvent. The wet gel was then dried to obtain RF aerogel. The drying was performed at 80°C for 5 hours and at 150°C for 2 hours. The RF aerogel thus obtained was carbonized by heating at 100, 200, and 400°C for 1 hour each in an inert atmosphere, and finally at 800°C for 3 hours to obtain a carbon scaffold. Other matters were performed in the same manner as in Example 1 described above to obtain a negative electrode active material.

[0126]

[0127] Experimental Example 1: Measurement of the initial electrochemical capacity and efficiency of the carbon scaffold itself.

[0128] Before silicon deposition, the carbon scaffolds according to the above examples and comparative examples were used as anode active materials, and the initial electrochemical capacity and efficiency of the carbon scaffolds themselves were measured. More specifically, the anodes were manufactured with a ratio of anode active material:binder of 7:3. At this time, the carbon scaffolds according to the above examples and comparative examples were used as the anode active materials. Polyacrylic acid (PAA) was used as the binder. A secondary battery (2032 Coin Half Cell) was manufactured using the manufactured anodes. At this time, lithium metal was used as the counter electrode.

[0129] For the manufactured secondary batteries, the charge capacity and discharge capacity were measured under 0.1C rate (1C = 2500 mA / gC) conditions, and the charge / discharge efficiency was calculated and shown in Table 1 below. The charge / discharge efficiency was calculated as the ratio of the discharge capacity to the charge capacity (discharge capacity / charge capacity).

[0130] Charge / discharge efficiency (%) Example 125.8 Example 233.9 Example 338.3 Example 443.8 Comparative example 122.2

[0131] Referring to Table 1, it was confirmed that the charge / discharge efficiency of the carbon scaffolds themselves according to the examples formed by agglomerating carbon structures was superior to that of the comparative examples formed by carbonizing polymers. Furthermore, it was confirmed that the charge / discharge efficiency of the carbon scaffolds themselves increased as the graphene content increased.

[0132]

[0133] (Manufacturing Example 1)

[0134] An anode was manufactured using the anode active material according to Example 1 described above. Polyacrylic acid (PAA) was used as the binder required for the manufacture of the anode. Super C65 (Timcal) was used as the conductive agent. At this time, the ratio of anode active material:binder:conductive agent was controlled to be 6:3:1. Thereafter, a secondary battery (2032 Coin Half Cell) was manufactured using the manufactured anode.

[0135]

[0136] (Manufacturing Example 2)

[0137] A secondary battery was manufactured in the same manner as in Manufacturing Example 1 described above, except that the negative active material according to Example 2 was used.

[0138]

[0139] (Manufacturing Example 3)

[0140] A secondary battery was manufactured in the same manner as in Manufacturing Example 1 described above, except that the negative active material according to Example 3 was used.

[0141]

[0142] (Manufacturing Example 4)

[0143] A secondary battery was manufactured in the same manner as in Manufacturing Example 1 described above, except that the negative active material according to Example 4 was used.

[0144]

[0145] Test Example 2: Initial efficiency by silicon deposition amount

[0146] The efficiency of secondary batteries according to the above-described manufacturing examples was measured according to the amount of silicon deposited. More specifically, in the above-described examples, multiple negative active materials were manufactured by varying the amount of silicon deposited. Subsequently, secondary batteries were manufactured according to the above-described manufacturing examples.

[0147] The efficiency of the secondary batteries was measured by charging and discharging each of the secondary batteries according to the manufacturing examples described above, and the charge and discharge capacities were measured. The measured charge and discharge capacities were then used to calculate the charge and discharge efficiency.

[0148] Charging of secondary batteries was performed under controlled conditions of 0.5C, 0.5mV CC-CV, and a cut-off current of 0.005C. CC-CV stands for constant current-constant voltage charging.

[0149] The discharge of secondary batteries was performed under control at 0.5C and a cutoff voltage of 1.0 V.

[0150] In this experimental example, the 1C rate was defined as 2,500 mAh / gSi, and after calculating the current, charging and discharging was performed at 0.5C according to the weight (g) of Si (active material) of the electrode.

[0151] Figure 1 is a graph showing the efficiency of secondary batteries according to silicon content.

[0152] Referring to Figure 1, it was confirmed that the charge / discharge efficiency (CE%) of the secondary battery increased as the amount of silicon deposition increased. The charge / discharge efficiency of the secondary battery shows a similar trend to the charge / discharge efficiency of the carbon scaffold itself. That is, as the content of graphene in the negative active material increased, the charge / discharge efficiency of the secondary battery increased. Therefore, it is expected that the charge / discharge efficiency of the secondary battery will also be inferior when using a polymer-derived carbon scaffold, which had a lower charge / discharge efficiency than a carbon scaffold manufactured using a carbon structure. Consequently, it was confirmed that the efficiency of the secondary battery can be improved by improving the efficiency of the carbon scaffold itself.

[0153]

[0154] The present invention has been described in more detail through drawings and examples. However, the configurations described in the drawings or examples described in this specification are merely embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

Claims

1. Carbon scaffold with porous structure; and Comprising silicon particles distributed in the pores of the above carbon scaffold; The above carbon scaffold, A negative electrode active material comprising a plurality of carbon structures that are cohesively aggregated.

2. In paragraph 1, The above carbon structure is a negative electrode active material, which is any one of a linear carbon structure, a planer carbon structure, a ball-shaped carbon structure, and a combination thereof.

3. In paragraph 2, A negative electrode active material having a content of the above-mentioned planar carbon structure higher than the content of the above-mentioned linear carbon structure.

4. In paragraph 2, The linear carbon structure is a negative active material including any one of carbon nanotubes, carbon nanofibers, and combinations thereof.

5. In paragraph 2, The above planar carbon structure is a negative electrode active material including graphene.

6. In paragraph 1, The above negative active material has a D50 of 0.5 to 20.0㎛.

7. In paragraph 6, The above negative active material has a D50 of 3 to 15 μm.

8. In paragraph 1, The specific surface area of ​​the above carbon scaffold is 300-500 m 2 / g negative active material.

9. In paragraph 1, The pore volume of the above carbon scaffold is 0.8–2.0 cm 2 / g negative active material.

10. In paragraph 1, The above carbon scaffold is a negative active material having an average pore size (width) of 2 to 8 nm.

11. In paragraph 1, A negative active material characterized in that the silicon particles are deposited in the pores of the carbon scaffold.

12. In paragraph 1, A negative active material further comprising a coating layer provided on the surface of the carbon scaffold.

13. A step of preparing a carbon slurry in which a carbon structure is dispersed in a solvent; A step of spray drying the above carbon slurry to obtain a carbon scaffold with a porous structure; and A method for manufacturing a negative electrode active material, comprising: a step of providing silicon to the carbon scaffold.

14. In paragraph 13, The step of providing the above silicon is: A method for manufacturing a negative electrode active material, the method comprising depositing a silicon precursor fluid into the pores of the carbon scaffold at 400 to 900°C.

15. In paragraph 13, A method for manufacturing a negative electrode active material, wherein the carbon structure is any one of a linear carbon structure, a planer carbon structure, a ball-shaped carbon structure, and a combination thereof.

16. In paragraph 13, A method for manufacturing the above negative active material is as follows: A method for manufacturing a negative electrode active material further comprising the step of providing a coating layer on the surface of a carbon scaffold.

17. Negative current collector; and A negative electrode comprising a negative electrode active material according to any one of claims 1 to 12, and comprising a negative electrode active material layer positioned on one or both surfaces of the negative electrode current collector.

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