Silicon-based anode material containing high content of silicon, and secondary battery comprising same

Abstract

The present invention relates to a silicon-based anode material and a secondary battery comprising same. The silicon-based anode material comprises: a carbon-based structural reinforcing body; and silicon particles bonded to the carbon-based structural reinforcing body, wherein the amount of silicon elements is 80-99 wt% and the amount of carbon elements is 1-20 wt% on the basis of the total weight of the silicon-based anode material, and the crystallite size of the silicon particles is 60 nm or less.

Description

Silicon-based negative electrode material containing a high content of silicon and a secondary battery containing the same

[0001] The present invention relates to a silicon-based negative electrode material containing a high content of silicon and a secondary battery containing the same.

[0002] The performance improvement of secondary batteries is based on the components of positive electrode materials, negative electrode materials, and electrolyte.

[0003] Among the above components, graphite-based materials, which are mainly used as cathode materials, are commercially available due to their excellent electrochemical performance and low cost, but their theoretical capacity is limited to 370 mAh / g, which limits their application to high-capacity secondary batteries.

[0004] To overcome the above limitations, non-graphite anode materials such as silicon, tin, and germanium are emerging as alternative materials. Among them, silicon is being widely studied as an anode material that can replace graphite due to its large lithium ion storage capacity and advantageous material supply. However, unlike graphite, which stores lithium ions in the form of intercalation between structures, silicon stores lithium ions in an alloy format, and due to the material's characteristics, it experiences greater volume expansion than graphite during the charging process. This volume expansion not only acts as mechanical stress on the battery, but also causes damage to the silicon material itself during the charge and discharge process, resulting in a decrease in the performance of the secondary battery.

[0005] To prevent this phenomenon, efforts have been made to improve the lifespan of silicon-based anode materials by reducing the size of silicon particles to the nanometer level, composites using materials such as carbon and polymers, or coating them to minimize the mechanical stress exerted on the anode plate by the material's volume expansion. However, the silicon content of silicon-carbon composites produced through these methods is limited to a maximum of 50-60 wt%, limiting the mass capacity to 2,000 mAh.

[0006] Recently, as the demand for high-capacity and high-speed charging and discharging has increased, research is being conducted on high-capacity cathode materials exceeding 3000 mAh / g, and one of the methods being studied is a method using micro-sized silicon alone.

[0007] Prior art 1 (KR10-2530678B1) has an average particle diameter (D 50 ) discloses a method of producing silicon particles having a size of 1 to 30 μm and crushing them with a classifier. However, the micro-sized silicon particles produced by this crushing method have limitations in that they have an irregular shape and the crystal grain size cannot be controlled to be less than 100 nm.

[0008] Looking at prior art 2 (KR10-2454375B1), the average particle diameter (D) is 1 ㎛ to 10 ㎛ 50 ) is coated with a carbon material such as graphite and soft carbon to prevent pulverization of silicon particles that may occur during the charge / discharge process and to reduce stress due to volume change.

[0009] Prior art 3 (KR10-2022-0156964A) discloses a composite particle comprising a porous carbon framework including micropores and mesopores and a plurality of nanoscale elemental silicon domains positioned within the pores of the carbon framework, wherein the particulate material comprises 25 to 65 wt% of silicon and the pores have a diameter of 3 to 12 nm. Therefore, it is presumed that the size of the silicon particles actually manufactured in Prior Art 3 is disclosed to be 12 nm or less.

[0010] The purpose of the present invention is to provide a silicon-based negative electrode material that can significantly improve the capacity, efficiency, capacity retention rate, and lifespan of a secondary battery when used as a negative electrode material of a secondary battery, and a secondary battery including the same.

[0011] The purpose of the present invention is not limited to the aforementioned purposes, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0012] In order to achieve the above object, according to a first aspect of the present invention, a silicon-based negative electrode material can be provided, which includes a carbon-based structural reinforcing body and silicon particles bonded to the carbon-based structural reinforcing body, wherein the content of silicon element is 80 to 99 wt% relative to the total weight of the silicon-based negative electrode material, the content of carbon element is 1 to 20 wt%, and the crystallite size of the silicon particles is 60 nm or less.

[0013] The above silicon-based negative electrode material may have a tap density of 1.0 (g / cc) or more.

[0014] The above silicon-based cathode material has a specific surface area (BET) of 2 m 2 / g can be less.

[0015] The above silicon-based negative electrode material may have a sphericity of 80% or more.

[0016] The above silicon-based negative electrode material has an average particle diameter (D 50 ) can be 2 to 10 μm.

[0017] The carbon-based structural reinforcing body of the silicon-based negative electrode material may include one or more materials selected from the group consisting of carbon fiber, carbon nanotube, carbon black, pitch, graphite flake, and graphite.

[0018] The capacity of the above silicon-based negative electrode material can satisfy 3000 mAh / g or more.

[0019] According to a second aspect of the present invention, a negative electrode active material including a silicon-based negative electrode material according to the first aspect of the present invention can be provided.

[0020] According to a third aspect of the present invention, a secondary battery including a negative electrode active material according to the second aspect of the present invention can be provided.

[0021] The silicon-based negative electrode material according to the present invention satisfies the requirement that the silicon crystal grain size is 60 nm or less while containing a high amount of silicon, and thus a silicon-based negative electrode material having a novel structure can be provided.

[0022] The silicon-based negative electrode material according to the present invention can significantly improve the capacity, initial efficiency, capacity retention rate, and lifespan of a secondary battery.

[0023] In addition, since the silicon-based negative electrode material according to the present invention is not manufactured by crushing bulk silicon, unlike the conventional technology, it has a high sphericity and a regular shape, making it easy to manufacture an electrode plate and having excellent process applicability.

[0024] In addition to the effects described above, the effects of the present invention are described together with the description of matters for carrying out the invention below.

[0025] Figure 1 is a schematic diagram of a silicon-based negative electrode material according to one embodiment of the present invention.

[0026] Figure 2 shows an SEM image of the silicon-based negative electrode material manufactured in Example 1.

[0027] Figure 3 shows an SEM image of the silicon-based negative electrode material manufactured in Comparative Example 1.

[0028] Figure 4 shows an SEM image of the silicon-based negative electrode material manufactured in Comparative Example 2.

[0029] Figure 5 shows an SEM image of the silicon-based negative electrode material manufactured in Comparative Example 3.

[0030] Figure 6 is a graph for evaluating life characteristics by plotting the capacity retention rate (%) against the number of charge / discharge cycles tested in Experimental Example 2.

[0031] Figure 7 shows a life evaluation graph tested in Experimental Example 3.

[0032] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0033] In this specification, when the terms "includes," "contains," "has," "consists of," "arranges," and "provides" are used for a component, other parts may be added unless "only" is used. When a component is expressed in the singular, it includes the plural unless otherwise explicitly stated.

[0034] Unless otherwise specified in this specification, units are assumed to be based on weight. For example, if only "%" is specified, it is interpreted as "weight % (wt%)."

[0035]

[0036] [Method of evaluating physical properties]

[0037] In the present invention, the crystal grain size is calculated using the Scherer equation from data measured by an XRD device (device name: panalytical - x'pert pro).

[0038] In the present invention, true density is measured by the pycnometer method using helium. Specifically, a container having a constant volume is filled with helium gas, and then a solid sample to be measured is placed therein, and the change in volume of the replaced helium gas is measured to calculate the density.

[0039] In the present invention, tap density is measured by placing a powder weighing about 50 g in a graduated cylinder using a jolting volumeter and tapping for 5 minutes to check the volume.

[0040] In the present invention, the elemental content of oxygen and hydrogen (unit: weight) is analyzed using an ONH analyzer (Oxygen / Nitrogen / Hydrogen Analyzer), and the elemental content of silicon and carbon (unit: weight) is measured using a CS analyzer (Carbon / Sulfur Analyzer) using a combustion method to measure the carbon (C) content in the measurement target, and then the remaining content is measured as the silicon (Si) content.

[0041] In the present invention, the specific surface area (BET) is measured using Micro meritics ASAP 2460.

[0042] In the present invention, sphericity is measured by designating horizontal and vertical axes to intersect at 90° from the center of the silicon particle, and converting the length of the vertical axis to the length of the horizontal axis within the silicon particle into a percentage (%).

[0043] In the present invention, the average particle diameter (D50) is measured by laser diffraction using a laser diffraction particle size analyzer (Master sizer 4000, Malvern). When interpreting components in this specification, even if not explicitly stated otherwise, they are interpreted as including a margin of error.

[0044]

[0045] Hereinafter, the present invention will be described in more detail.

[0046] Referring to FIG. 1, a silicon-based negative electrode material according to the present invention includes a carbon-based structural reinforcing body and silicon particles bonded to the carbon-based structural reinforcing body.

[0047] The above silicon-based negative electrode material is characterized by using a carbon-based structural reinforcing body, and therefore, unlike negative electrode materials using only silicon, it may contain a certain amount of carbon or more by weight. However, it is preferable to control the content of silicon and carbon elements in order to improve the capacity of the secondary battery. From this perspective, the content of silicon element relative to the total weight of the silicon-based negative electrode material of the present invention may be 80 to 99 wt%, and the content of carbon element may be 1 to 20 wt%. In addition, for example, the content of silicon element relative to the total weight of the silicon-based negative electrode material of the present invention may be 81 to 95 wt%, and the content of carbon element may be 5 to 19 wt%.

[0048] The silicon-based negative electrode material according to the present invention may have a silicon particle crystallite size of 60 nm or less, for example, 50 nm or less, for example, 40 nm or less. If the silicon particle crystallite size exceeds the upper limit, when applied as a secondary battery negative electrode material, there is a high possibility that a large volume change will occur during the charge and discharge process of the secondary battery, which may cause a problem of rapid deterioration in the lifespan. From this perspective, there is no specific lower limit on the silicon particle crystallite size, but it is preferably 0.1 nm or more.

[0049] The particle size of the silicon-based negative electrode material according to the present invention may be 2 to 10 μm, for example 3 to 8 μm, for example 4 to 7 μm. If it is less than the lower limit, the surface area of ​​the powder increases, so that when applied as a negative electrode material, the initial Coulombic Efficiency (ICE) is measured low, and there may be a problem that dispersion is not easy when manufacturing a negative electrode slurry. If it is more than the lower limit, there may be a problem that it is not appropriate because it is difficult to control the thickness and density of the negative electrode plate when manufacturing a secondary battery negative electrode plate.

[0050] Conventional silicon-carbon composite anode materials have a silicon content of up to 50 to 60% and a capacity of about 2,000 mAh / g, but the silicon-based anode material according to the present invention can achieve a high capacity of 3,000 mAh / g or more by including a high content of silicon.

[0051] According to one embodiment of the present invention, the silicon-based negative electrode material has a tap density of 1.0 (g / cc) or more. A larger tap density is advantageous in that it can increase the energy density per volume of a secondary battery. Assuming that the micro-sized negative electrode material according to the present invention has an FCC (Face Centered Cubic) structure, which is an ideal packing form, the tap density of the silicon-based negative electrode material reflecting the true density of the structure may be 1.7 g / cc or less, or 1.6 g / cc or less. While the tap density of a conventional silicon-carbon composite negative electrode material is about 0.8 g / cc due to its density and structure, the silicon-based negative electrode material according to the present invention satisfies a tap density of 1.0 g / cc or more, thereby having the advantage of increasing the energy density per volume in a secondary battery.

[0052] According to one embodiment of the present invention, the silicon-based negative electrode material has a specific surface area (BET) of 2 m 2 / g or less. When charging a secondary battery, an SEI layer (Solid Electrolyte Interphase layer) is irreversibly formed on the surface of the negative electrode material. Therefore, if the specific surface area of ​​the negative electrode material is large, the initial efficiency may be low. Therefore, the smaller the specific surface area value, the more advantageous it is. Therefore, the specific surface area of ​​a silicon-based negative electrode material is 0.01 m, which is the lower limit of the BET measurement value. 2 / g can be more than that.

[0053] In addition, according to one embodiment of the present invention, the silicon-based negative electrode material can satisfy a sphericity of 80% or more, for example, 90% or more.

[0054] In the present invention, since a silicon anode material is manufactured by placing a micro-sized carbon-based structural reinforcing body into a chemical vapor deposition (CVD) reactor and then introducing a silicon source gas, a separate pulverization and classification process is not required, and thus it is possible to manufacture a silicon anode material with high sphericity and uniform shape.

[0055] According to an example, the carbon-based structural reinforcement may include one or more materials selected from carbon fibers, carbon nanotubes, carbon black, pitch, graphite flakes, and graphite. When carbon black is used, it has advantages such as improved electrical conductivity, enhanced mechanical stability, and increased surface area. Therefore, a material manufactured using carbon black may be preferably used as the carbon-based structural reinforcement.

[0056] In the present invention, a negative electrode material is manufactured by depositing silicon on a carbon-based structural reinforcing body, so the particle size (D) of the carbon-based structural reinforcing body 50 ) compared to the particle size (D) of the final cathode material 50 ) becomes about 1 to 2 μm larger. Therefore, it is desirable to select the size of the carbon-based structural reinforcement according to the size of the final negative electrode material to be manufactured. For example, the carbon-based structural reinforcement has a particle size (D ) of 1 to 6 μm. 50) can have.

[0057] When manufacturing using the conventional manufacturing method of crushing bulk silicon to manufacture micro-sized silicon, it is difficult to control the particle size, and a lot of fine particles are inevitably generated during the process. Therefore, when applied as an anode material, the initial efficiency of the secondary battery is lowered due to the high surface area, and there is a high possibility that the lifespan is reduced due to side reactions with the electrolyte. In addition, there is a limitation that a classification process must be added to remove the silicon fine particles. On the other hand, the silicon-based anode material according to the present invention introduces a carbon-based internal framework while manufacturing a high-capacity silicon-based anode material, making it easy to control the particle size, and since there is almost no possibility of fine particles being generated, an additional classification process is not required. When applied as an anode material, the initial efficiency of the secondary battery can be increased, and the problem of reduced lifespan due to side reactions with the electrolyte can be improved.

[0058] Micro silicon, prepared by crushing and classifying bulk silicon as in the past, has a sphericity of less than 70%, resulting in irregular and angular shapes, which are disadvantageous for the production of uniform electrode plates. In contrast, the silicon-based anode material according to the present invention, which does not require a crushing process, has a high sphericity, enabling the production of uniform electrode plates and exhibiting high potential for industrial application.

[0059] According to another aspect of the present invention, an anode active material comprising the silicon-based anode material of the present invention can be provided. For example, the anode active material can be manufactured using only the silicon-based anode material of the present invention as a sole component, but can also be used in combination with other anode materials such as graphite, silicon, metal oxide, lithium metal oxide, etc. When the silicon-based anode material of the present invention is included as a component of the anode active material, when the total weight of the anode active material is 100 wt%, the silicon-based anode material of the present invention can be included in an amount of at least 1 wt% or more, for example, 2 wt% or more, 3 wt% or more, 4 wt% or more, or 5 wt% or more.

[0060] Hereinafter, the present invention will be described in more detail through examples and experimental examples. However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0061]

[0062] <Experimental Example 1> Manufacturing and Characterization of Negative Electrode Materials

[0063] Example 1

[0064] Carbon black (Super P from Imerys) was dispersed in ethanol to make a slurry, which was then spray dried to obtain particle size (D 50 ) was manufactured as a carbon-based structural reinforcement having a thickness of 7 μm. Then, the carbon-based structural reinforcement was placed in a CVD reactor and heated to 486°C. Then, a mixture of silane (SiH4) gas (flow rate: 100 sccm) and H2 gas (flow rate: 400 sccm) was introduced for 4 hours to perform a silicon deposition reaction on the carbon-based structural reinforcement. Then, the final product was recovered by cooling while supplying Ar gas and used as the silicon-based anode material of Example 1.

[0065] Comparative Example 1

[0066] Ar gas was introduced into a CVD reactor, and the reactor was heated to 900°C under a pressure of 5 bar. Then, a silicon source gas (a mixture of 3 mol% dichlorosilane (SiH2Cl2) gas and 30 mol% trichlorosilane (SiHCl3) gas) together with 67 mol% H2 gas were simultaneously introduced into one reactor. Then, the silicon source gas mixture was decomposed by reacting in one reactor for about 40 minutes to produce micro-sized silicon particles. Then, the final product was recovered by cooling while supplying Ar gas, and used as a silicon-based anode material of Comparative Example 1.

[0067] Comparative Example 2

[0068] Metal silicon (MG-Si from Ferroglobe) was pulverized through jet milling, and fine and coarse particles were removed using an air classifier to select micro-sized silicon, which was used as the silicon-based negative electrode material of Comparative Example 2.

[0069] Comparative Example 3

[0070] Polysilicon (11-nine purity from OCI) was pulverized through jet milling, and fine and coarse particles were removed using an air classifier to select micro-sized silicon, which was used as the silicon-based negative electrode material of Comparative Example 3.

[0071] Comparative Example 4

[0072] Activated carbon raw material (KL-OR from Zhengzhou Kelin Water Purification Material Co., Ltd.) was crushed through a bead mill and then spheroidized through spray drying to obtain particle size (D 50 ) was used as a carbon-based structural reinforcement. The activated carbon was placed in a CVD reactor and heated to 486°C. Then, a mixture of silane (SiH4) gas (flow rate: 100 sccm) and H2 gas (flow rate: 400 sccm) was introduced for 2 hours to perform a silicon deposition reaction on the carbon-based structural reinforcement. Then, the final product was recovered by cooling while supplying Ar gas and used as a silicon-based negative electrode material of Comparative Example 4.

[0073] Comparative Example 5

[0074] The same carbon-based structural reinforcement used in Example 1 was placed in a CVD reactor and heated to 486°C. Then, silane (SiH4) gas (flow rate: 100 sccm) and H 2　A mixture of gases (flow rate: 300 sccm) was introduced for 4 hours to conduct a silicon deposition reaction on a carbon-based structural reinforcement. Then, the reactor temperature was heated to 600°C while supplying Ar gas. Afterwards, a mixture of acetylene gas (flow rate: 500 sccm) and Ar gas (flow rate 400 sccm) was introduced for 5 hours to conduct carbon coating. Then, the final product, which was recovered by cooling while supplying Ar gas, was used as a silicon-based anode material in Comparative Example 5.

[0075] The results of the above-mentioned manufactured Example 1 and Comparative Examples 1 to 5 were measured for physical properties according to the [Method for Physical Property Evaluation] of this specification, and the results are shown in Table 1 below.

[0076] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Silicon content (wt%) 86 100 100 100 5 28 4 Carbon content (wt%) 1 3 0 0 4 8 16 XRD grain size (nm) 3 2 5 7 1 4 2 1 0 5 5 6 7 True density (g / cc) 2.2 3 2.3 2.3 2.3 2.3 2.3 2.1 5 2.1 5 Tap density (g / cc) 1.0 1.0 1.0 1.0 0.8 1.0 BET (m 2 / g)0.560.540.550.575.420.57Sphericity(%)918965668566D of cathode material 50 (㎛)9.645.386.6610.76.6810.7

[0077] * In Example 1, in addition to silicon and carbon, oxygen and hydrogen are contained at approximately 1 wt%.

[0078]

[0079] Referring to Table 1 above, Example 1 had similar physical properties such as true density, tap density, and BET when compared to the silicon-based anode materials of Comparative Examples 1 to 5, but there was a difference in the silicon content and silicon grain size. Example 1 is a silicon-based anode material with a silicon content of 86 wt%, and unlike Comparative Examples 1 to 3 and 5, which were manufactured into micro-sized silicon by pulverizing, it exhibited a small crystal grain size of 60 nm or less as intended in the present invention. In addition, Comparative Examples 1 to 3 had a higher silicon content than Example 1, and thus the capacity was measured to be higher. Due to these structural features, as confirmed through experiments in Experimental Examples 2 and 3 below, Example 1 showed improved secondary battery performance such as capacity retention and lifespan compared to the Comparative Examples. In addition, it was found that the sphericity was much higher than that of the pulverized silicon (Comparative Examples 2 to 3), which is advantageous in the manufacture of electrode plates.

[0080]

[0081] <Experimental Example 2> Half Cell Test

[0082] 1) A conductive material was prepared by mixing conductive carbon black and carbon nanotubes (SWCNT) at a weight ratio of 9:1.

[0083] 2) CMC and SBR were mixed in a weight ratio of 3:7 to prepare a binder.

[0084] 3) The negative electrode material manufactured in Example 1, the conductive material prepared in 1), and the binder prepared in 2) were mixed in a ratio (weight ratio) of 8:1:1 to prepare a negative electrode slurry.

[0085] 4) The cathode slurry of 3) above was applied to a copper foil having a thickness of 18 ㎛, and after primary drying, secondary drying was performed in a vacuum oven at a temperature of 100°C for more than 6 hours to manufacture an electrode plate.

[0086] 5) After rolling the electrode plate of 4) above, a negative electrode plate was manufactured by punching it to a diameter of 16 mm.

[0087] 6) The electrochemical characteristics were confirmed by manufacturing a coin cell using lithium metal (Li metal) as a counter electrode on the above-mentioned manufactured negative electrode plate.

[0088] 7) Charging CC / CV 0.005V / 0.005C, discharging 1.5V, rate 0.1C were performed to measure the initial discharge capacity and initial efficiency, and the capacity retention rate (%) for the number of charge / discharge cycles was measured as the lifespan.

[0089]

[0090] Except that the “negative electrode material manufactured in Example 1” of the above 3) was replaced with a silicon-based negative electrode material manufactured in Comparative Examples 1 to 4, a half-cell test was conducted using the coin cells manufactured in Comparative Examples 1 to 4 in the same manner as 1) to 7), and the results are shown in Table 2 and Fig. 6 below.

[0091] Classification Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Initial discharge capacity (mAh / g) 30 10 34 18 27 8 4 30 8 11 8 5 1 Initial efficiency (%) 9 1.0 9 1.9 8 2.7 8 7.6 9 0.9 Capacity retention rate (%) (@10 cycles) 8 27 36 75 5 9 0

[0092] As can be seen in Table 2 above, when the negative electrode material according to Example 1 was used, the initial discharge capacity was somewhat lower than when the negative electrode materials according to Comparative Examples 1 to 3 were used. This is because the negative electrode materials of Comparative Examples 1 to 3 were manufactured with 100 wt% of silicon. However, it was confirmed that the capacity retention rate of the negative electrode material of Example 1 of the present invention was significantly improved compared to Comparative Examples 1 to 3. On the other hand, the silicon-based negative electrode material of Comparative Example 4 had a low silicon content of 52 wt%, and therefore, as confirmed in the half-cell test, the capacity was very low compared to Example 1. Therefore, even if the capacity retention rate is higher than that of Example 1, the performance as a negative electrode material is judged to be worse than that of Example 1 because the capacity itself is low.

[0093]

[0094] <Experimental Example 3> Full Cell Test

[0095] In Example 1, 5 wt% of the negative electrode material and 95 wt% of graphite were mixed to prepare a negative electrode active material, conductive carbon black (super P) carbon nanotubes (SWCNT) were mixed in a weight ratio of 9:1 to prepare a conductive material, and CMC (sodium slat of carboxymethyl cellulose) and SBR were mixed in a weight ratio of 3:7 to prepare a binder. The negative electrode active material, conductive material, and binder were mixed in a weight ratio of 95.8:1:3.2 to obtain a negative electrode slurry, which was then applied to a copper foil having a thickness of 18 ㎛, dried, rolled, and heat-treated in a vacuum oven at 100°C for 24 hours to punch out a 16 mmØ negative electrode plate. The positive electrode was prepared by punching a 14mmØ plate made by mixing the positive electrode material NCM811, conductive carbon black (Super P), and PVDF in a weight ratio of 96:2:2. A coin full cell (CR2032) was manufactured using the above negative and positive electrode plates, and the electrochemical characteristics were confirmed. The initial 2 cycles were formed with a charge CC / CV of 4.25V / 0.05C, a discharge CC of 2.5V, and a rate of 0.1C, and then the life characteristics were measured for 100 cycles under the same charge and discharge conditions but at a rate of 0.1C, and the results are shown in Fig. 7. The silicon-based negative electrode material of Comparative Example 5 had a high silicon content similar to that of the present invention, but the crystal grain size of the silicon particles was measured to be 67 nm, which exceeds 60 nm. As a result, as confirmed in FIG. 7, which is the result of a full cell test, the capacity retention rate of the secondary battery was lowered compared to Example 1, resulting in a deteriorated lifespan.

[0096]

[0097] Although the embodiments of the present specification have been described in more detail with reference to the attached drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be implemented without departing from the technical spirit of the present specification. Therefore, the embodiments disclosed in this specification are not intended to limit the technical spirit of the present specification, but to explain, and the scope of the technical spirit of the present specification is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of protection of this specification should be interpreted by the claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of rights of this specification.

Claims

1. As a silicon-based negative electrode material, Comprising a carbon-based structural reinforcement and silicon particles bonded to the carbon-based structural reinforcement, The content of silicon element relative to the total weight of the above silicon-based negative electrode material is 80 to 99 wt%, and the content of carbon element is 1 to 20 wt%. A silicon-based negative electrode material having a crystallite size of 60 nm or less.

2. In paragraph 1, A silicon-based negative electrode material having a tap density of 1.0 (g / cc) or more.

3. In paragraph 1, The specific surface area (BET) is 2 m 2 / g or less, silicon-based negative electrode material.

4. In paragraph 1, A silicon-based cathode material with a spherical density of 80% or more.

5. In paragraph 1, Average particle diameter (D 50 ) is a silicon-based negative electrode material with a diameter of 2 to 10 μm.

6. In paragraph 1, A silicon-based negative electrode material, wherein the carbon-based structural reinforcement comprises one or more materials selected from the group consisting of carbon fiber, carbon nanotube, carbon black, pitch, graphite flake, and graphite.

7. In paragraph 1, A silicon-based negative electrode material with a capacity of 3000 mAh / g or more.

8. A negative electrode active material comprising a silicon-based negative electrode material according to any one of claims 1 to 7.

9. A secondary battery comprising a negative electrode active material according to Article 8.

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