Negative electrode active material, method for producing the same, and lithium secondary battery including the same

Abstract

To provide a negative electrode active material for a secondary battery with a long life characteristic that a stably charging / discharging behavior can be made even after it is used for a long time while having a high capacitance and a high energy density.SOLUTION: The present invention relates to a negative electrode active material for a lithium secondary battery, containing a core containing a metal particle and a shell layer formed in an outside part of the core. The shell layer contains a metal carbide particle and a carbon system material. A number density in the shell layer of the metal carbide particle (number / μm2) is 50 or more and 100 or less. The present invention relates to a manufacturing method and a lithium secondary battery containing them.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a negative electrode active material, a method for manufacturing the same, and a lithium secondary battery including the same. Specifically, silicon carbide (SiC) particles are introduced into a shell layer at a specific density, and stable behavior is possible even after long-term charge / discharge, and the present invention relates to a negative electrode active material that improves battery life, a method for manufacturing the same, and a lithium secondary battery including the same.

Background Art

[0002] Lithium ion batteries (LIBs) have a high energy density, are easy to design, and are adopted and used as the main power supply source of mobile electronic devices. In the future, their application scope will become wider in electric vehicles or power storage devices for new renewable energy.

[0003] In order to apply to new application fields, research on LIB materials having characteristics such as higher energy density and longer life has been continuously demanded. In particular, in the case of negative electrode materials, research has been conducted on various substances such as silicon, tin, and germanium in addition to carbon.

[0004] Among them, silicon-based negative electrode materials have an extremely high theoretical capacity compared to the currently commercialized graphite negative electrode materials and have attracted much attention. However, silicon-based negative electrode materials have problems such as a decrease in electrochemical properties due to the formation of an unstable SEI (Solid Electrolyte Interphase) layer by the side reaction between the silicon surface and the electrolyte, and pulverization of the electrode material due to internal stress caused by the rapid volume expansion that occurs during charge / discharge.

[0005] To solve this problem, research has been conducted on nanostructuring, surface modification, and composite formation with different substances of silicon-based anode materials. In particular, methods of surface coating or composite formation with carbon materials have been widely studied mainly in the industrial field. Various surface treatments using carbon materials require complex and costly processes. Although some lifetime characteristics of silicon-based anode materials are improved through surface treatments using carbon materials, fundamental modification of the material design concept is required to cope with the large volume changes that occur during charging / discharging of silicon-based anode materials.

[0006] Therefore, there is a current situation where technological development regarding structural modification of high-capacity silicon-based anode active materials is required to suppress the volume expansion of silicon-based anode materials and improve the unstable lifetime characteristics of silicon-based anode materials.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention was devised to solve the above problems, and an object thereof is to provide a negative electrode active material for a secondary battery having a long lifetime characteristic capable of stable charging / discharging behavior even after long-term use while having a high capacity and a high energy density.

[0008] Also, it can be considered that the present invention also aims to provide the method for manufacturing the negative electrode active material and the lithium secondary battery including the negative electrode active material.

[0009] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those having ordinary knowledge in the technical field from the following description.

Means for Solving the Problems

[0010] According to an embodiment of the present invention, it includes a core containing metal particles and a shell layer formed outside the core, the shell layer includes metal carbide particles and a carbon-based substance, and the number density (number / μm 2 ) in the shell layer of the metal carbide particles is 50 or more and 100 or less, and a negative electrode active material is provided.

[0011] According to an embodiment of the present invention, there is provided a method for manufacturing a negative electrode active material, including the steps of: dispersing metal nanoparticles in a solvent (S1); spray-drying the dispersed solution to produce spherical metal precursor powder (S2); mixing the spherical metal precursor powder with an amorphous carbon precursor and crystalline carbon for complexing (S3); and heat-treating at 1100°C to 1400°C for 3 to 8 hours (S4).

[0012] According to an embodiment of the present invention, a lithium secondary battery including the negative electrode active material is provided.

Effects of the Invention

[0013] The negative electrode active material according to an embodiment of the present invention is composed of a core part containing silicon particles and a shell part containing silicon carbide particles and a carbon-based substance surrounding it. In the present invention, the silicon particles can improve the energy density of the composite material as a high-capacity negative electrode active material, and the internal pores can efficiently accommodate the volume expansion during charging of the silicon particles to prevent structural destruction of the composite.

[0014] In addition, the carbon-based substance can improve the life characteristics of the negative electrode active material through a stable electrochemical reaction with the electrolyte solvent at the outermost part of the shell part.

[0015] Furthermore, silicon carbide (SiC) particles can efficiently prevent the destruction of the shell part due to the stress generated during the expansion of the core part by strengthening the mechanical strength of the shell part, and contribute to the manifestation of stable life characteristics.

[0016] The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, various changes may be made to the embodiments, and the scope of the patent application is not limited or restricted by such embodiments. It should be understood that all changes, equivalents, or alternatives to the embodiments are included in the scope of the rights.

[0019] The terms used in the embodiments are for illustrative purposes only and are not to be construed as having an intention to limit. Singular expressions include plural expressions unless the context clearly indicates a different meaning. In this specification, terms such as "including" or "having" indicate the presence of the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0020] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this embodiment belongs. Commonly used predefined terms shall be construed to have a meaning consistent with the meaning they have in the context of the relevant art and shall not be construed in an idealized or overly formal sense unless clearly defined herein.

[0021] Also, in the description with reference to the accompanying drawings, the same components shall be given the same reference numerals regardless of the reference signs, and redundant descriptions thereof shall be omitted. In the description of the embodiments, when it is determined that the specific description of the related known technology makes the gist of the embodiments needlessly ambiguous, the detailed description thereof shall be omitted.

[0022] According to one aspect of the present invention, there is provided a negative electrode active material including a core containing metal particles and a shell layer formed outside the core, the shell layer containing metal carbide particles and a carbon-based substance, wherein the number density (number / μm 2 ) of the metal carbide particles in the shell layer is 50 or more and 100 or less.

[0023] The metal particles contained in the negative electrode active material core include one or more selected from the group consisting of Si, Al, Zn, Ca, Mg, Fe, Mn, Co, Ni, and Ge, and for the purpose of improving energy density and capacity, preferably, may include silicon (Si) particles.

[0024] On the other hand, the silicon particles may more specifically be in the form of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and / or silicon alloy nanoparticles, and the shape of the silicon particles may have, for example, a flaky structure. Also, the preferred size of the silicon particles corresponds to a nano size of 1000 nm or less, and by including the silicon nanoparticles, it is easy to suppress the volume change of silicon due to charge / discharge.

[0025] More preferably, the average particle size of the silicon nanoparticles is D 50 It may be in the range of 50 nm to 200 nm based on a standard, and more preferably, it may be in the range of 80 nm to 130 nm.

[0026] When the average particle size (D 50 ) of the silicon nanoparticles is less than 50 nm, the manufacturing cost increases, and the battery capacity and efficiency decrease. When the average particle size exceeds 130 nm, it is not preferable in terms of the effect of suppressing volume change and battery life.

[0027] Thus, the negative electrode active material according to an embodiment of the present invention includes a core formed by including a plurality of nano-sized silicon particles. Compared with a core composed of single silicon particles, it has an effect of being more excellent in life characteristics and output characteristics, which can also be confirmed through the comparison of Embodiments 1 to 3 and Comparative Examples 1 to 3 described in detail later.

[0028] On the other hand, the core may contain a carbon-based material in addition to metal particles such as the silicon nanoparticles detailed above. The carbon-based material may specifically contain one or more of crystalline carbon and amorphous carbon.

[0029] The types of the crystalline carbon may include graphite-based carbon. More specifically, it may include natural graphite, artificial graphite, expanded graphite, etc.

[0030] The natural graphite is graphite calculated naturally, and examples include flake graphite and high crystalline graphite. The artificial graphite is graphite synthesized artificially, and is manufactured by heating amorphous carbon at a high temperature, and examples include primary graphite, electrographite, secondary graphite, graphite fiber, etc.

[0031] At the same time, expanded graphite is obtained by inserting chemicals such as acids or alkalis between the layers of graphite and heating it to expand the vertical layers of the molecular structure.

[0032] On the other hand, the type of the amorphous carbon is not greatly restricted, and it may be formed of one or more selected from the group consisting of sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin, or vinyl chloride resin, coal-based pitch, petroleum-based pitch, polyvinyl chloride, mesophase pitch, tar, block-copolymer, polyol, and low molecular weight middle oil. More specifically, it may be formed of coal-based pitch, petroleum-based pitch, or acrylic resin.

[0033] On the other hand, for the negative electrode active material according to an embodiment of the present invention, a shell layer containing metal carbide particles and a carbon-based material is formed outside the core detailed above.

[0034] By including such a shell layer, the contact between metal particles such as silicon nanoparticles present inside the core and the electrolyte solvent can be efficiently prevented, enabling a stable and reversible electrochemical reaction of the metal particles.

[0035] In addition, the metal carbide particles can efficiently prevent the destruction of the shell layer due to the stress generated during the expansion of the core part by strengthening the mechanical strength of the shell layer. The carbon-based material contained together with the metal carbide particles can improve the life characteristics of the negative electrode active material through a stable electrochemical reaction with the electrolyte solvent at the outermost shell of the shell layer.

[0036] Furthermore, the carbon-based material may be substantially the same / similar to the carbon-based material detailed above.

[0037] On the one hand, the metal carbide particles contained in the shell layer are homogeneously distributed within the shell layer and may be included at a number density of 50 to 100 (unit: number / μm 2 ). The number density is derived by observing the cross-section of the powder particles of the negative electrode active material and judging it as the number of metal carbide particles present per unit area (μm 2 ).

[0038] When the number density of the metal carbide particles in the shell layer exceeds the upper limit, the conductivity of lithium ions decreases, resulting in problems such as a decrease in output characteristics and battery efficiency. When it is less than the lower limit, since the mechanical strength of the shell layer is insufficient, it cannot effectively play the role of preventing the shell layer from being destroyed due to the volume change of the core. Therefore, it is appropriate that the number density of the metal carbide particles in the shell layer is 50 to 100, which is also confirmed to have differences in terms of life characteristics and output characteristics, etc. in the comparison of Embodiments 1 to 3 and Comparative Examples 4 to 5 described later.

[0039] Furthermore, the metal carbide particles contained in the shell layer may preferably be silicon carbide (SiC) particles, and their size is preferably 50 nm to 200 nm. When the size of the silicon carbide particles is less than the lower limit, the effect of improving the strength of the shell layer is not manifested. When the size exceeds the upper limit, there may be problems such as inhibiting the electrochemical reaction or disturbing the formation of the shell layer.

[0040] Furthermore, the thickness of the shell layer may be 100 nm to 3 μm. When the thickness of the shell layer is less than 100 nm, it may be damaged due to the volume change of silicon, which may have an adverse effect on the life characteristics. When the thickness exceeds 3 μm, not only does the capacity of the composite decrease due to an increase in the carbon amount, but the ion conductivity may also decrease, resulting in a decrease in output characteristics.

[0041] In addition, the negative electrode active material according to an embodiment of the present invention has a structure including the above-described core and shell layer, and its size may be 3 μm to 10 μm based on the average particle size (D 50 ), more preferably, it may be 5 μm to 8 μm.

[0042] When the average particle size (D 50 ) of the core-shell structure composite is less than 3 μm, there may be a problem that the dispersibility decreases in the electrode manufacturing process due to fine powder, and when it exceeds 10 μm, the electrode expansion due to the volume expansion of the composite deepens, and there is a risk of problems with life and safety.

[0043] According to one aspect of the present invention, there is provided a method for manufacturing a negative electrode active material including a step (S1) of dispersing metal nanoparticles in a solvent, a step (S2) of spray-drying the dispersed solution to produce spherical metal precursor powder, a step (S3) of mixing the spherical metal precursor powder with an amorphous carbon precursor and crystalline carbon to form a composite, and a step (S4) of heat-treating at 1100 °C to 1400 °C for 3 hours to 8 hours.

[0044] The step (S1) may be to disperse in a solvent using already manufactured metal nanoparticles, or may additionally include a step of manufacturing metal nanoparticles through a pulverization process of metal particles before the step (S1).

[0045] When additionally including the pulverization process, the metal particles are pulverized to a nano-sized size of a specific size (for example, 80 nm to 130 nm) through milling or the like, and the type of metal particles used here can be regarded as being substantially the same as the type of metal particles described in detail above.

[0046] As an example, the metal particles may be one or more silicon-containing nanoparticles selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles, and more preferably, silicon nanoparticles.

[0047] Further, the solvent may be a solvent containing one or more selected from the group consisting of methanol, ethanol, propanol, and butanol, and preferably may be a solvent containing isopropyl alcohol (IPA).

[0048] Also, the spherical metal precursor powder formed through the step (S2) is compounded under the conditions of air or an inert atmosphere for 1 minute to 24 hours at a reaction temperature of 40°C to 250°C through a compounder manufactured by itself using a hansol chemical by mixing an amorphous carbon precursor and a crystalline carbon precursor (step (S3)), and through the step (S3), a core-shell structure composite can be manufactured. The types of crystalline carbon and amorphous carbon mixed with the spherical metal precursor powder can be regarded as substantially the same as the crystalline carbon and amorphous carbon detailed above.

[0049] Furthermore, in the step (S3), by adjusting the mixing weight ratio of the spherical metal precursor powder and the amorphous carbon precursor within the range of 40:20 to 40:35, metal carbide particles such as silicon carbide (SiC) can be manufactured to have a number density of 50 or more and 100 or less in the negative electrode active material shell layer. When it is less than the said range (less than 40:20, for example, 40:10, etc.), the number density in the manufactured negative electrode active material shell layer may be less than 50. When it exceeds the said range (exceeds 40:35, for example, 40:40, etc.), the said number density will exceed 100.

[0050] In such a case, as described above, it will result in inferior results in terms of life characteristics and output characteristics.

[0051] Furthermore, the heat treatment process of the step (S4) is carried out at 1100°C to 1400°C for 3 hours to 8 hours. When it is lower than the said temperature range or the heat treatment time is less than that, silicon carbide particles such as silicon carbide (SiC) may not be sufficiently formed in the shell layer.

[0052] The composite powder formed through such a process can ultimately be used as the negative electrode active material according to an embodiment of the present invention after passing through a sieving process such as 325 mesh.

[0053] On the other hand, the present invention can also provide a lithium secondary battery including the negative electrode active material detailed above.

[0054] The lithium secondary battery according to an embodiment of the present invention includes a negative electrode, a positive electrode, an electrolyte, and a separator as components. The negative electrode may additionally include, in addition to the negative electrode active material described above, a negative electrode active material material that is commonly used as a negative electrode active material for lithium batteries in the art. As the commonly used negative electrode active material material, for example, one or more selected from the group consisting of lithium metal, metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbon-based materials may be included.

[0055] Also, the positive electrode may include a positive electrode active material. As the type of the positive electrode active material, it corresponds to a lithium-containing metal oxide and is applicable to the lithium secondary battery of the present invention as long as it is commonly used in the art.

[0056] Furthermore, the electrolyte may include a non-aqueous electrolyte containing a lithium salt. Specifically, a non-aqueous electrolyte solution, a solid electrolyte, an inorganic solid electrolyte, etc. may be used.

[0057] On the other hand, as the separator, a separator such as glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) can be disposed between the positive electrode and the negative electrode and included in the lithium secondary battery.

[0058] Hereinafter, the configuration of the present invention and the effects thereof will be described in more detail through embodiments and comparative examples. However, this embodiment is for more specifically explaining the present invention, and the scope of the present invention is not limited to this embodiment.

[0059] Embodiment (1) Manufacture of the negative electrode active material a) Embodiment 1 A solution in which silicon nanoparticles (D 50 = 93 nm) and a small amount of nano-carbon particles were dispersed was spray-dried to obtain a secondary particle precursor. The precursor was mixed with petroleum pitch and graphite in a weight ratio of 40:25:35 and put into a composite equipment (manufactured by Hansol Chemical Co., Ltd. itself), and then composite was carried out to obtain a composite powder. The composite powder was heat-treated at 1100 °C for 3 hours in an inert atmosphere, and then the powder obtained through a sieve (325 mesh) process was utilized as the negative electrode active material.

[0060] b) Embodiment 2 The negative electrode active material was manufactured in the same manner as in Embodiment 1 above, except that the ratio of the silicon precursor, petroleum pitch and graphite was manufactured in parts by weight of 40:22:38.

[0061] c) Embodiment 3 The negative electrode active material was manufactured in the same manner as in Embodiment 1 above, except that the ratio of the silicon precursor, petroleum pitch and graphite was manufactured in parts by weight of 40:28:32.

[0062] d) Comparative Example 1 The negative electrode active material was manufactured in the same manner as in Embodiment 1 above, except that the silicon precursor was applied to silicon microparticles (D 50 = 3 μm) during the composite process.

[0063] e) Comparative Example 2 The cathode active material was manufactured in the same manner as in Example 2 above, except that the silicon precursor was applied to silicon microparticles (D 50 = 3 μm) during the composite process.

[0064] f) Comparative Example 3 The negative electrode active material was manufactured in the same manner as in Embodiment 3 above, except that the silicon precursor was applied to silicon microparticles (D 50 = 3 μm) during the composite process.

[0065] g) Comparative Example 4 A negative electrode active material was produced in the same manner as in Embodiment 1 above, except that the ratio of the silicon precursor, petroleum pitch, and graphite was produced in parts by weight of 40:18:42.

[0066] h) Comparative Example 5 A negative electrode active material was produced in the same manner as in Embodiment 1 above, except that the ratio of the silicon precursor, petroleum pitch, and graphite was produced in parts by weight of 40:38:22.

[0067] i) Comparative Example 6 A negative electrode active material was produced in the same manner as in Embodiment 1 above, except that the heat treatment was carried out at 900 °C for 3 hours in an inert atmosphere.

[0068] (2) Method for Evaluating Physical Properties (Table 1) a) Particle Size Measurement The average particle sizes of the silicon particles and the precursor were measured using a particle size analyzer (Mastersizer 3000, Malvern Panalytical) with an organic solution in which the negative electrode active material produced by the method described above was dispersed.

[0069] b) Measurement of Carbon Content The carbon content of the produced negative electrode active material was measured through quantification of the gas generated by combustion at a high temperature (2200 °C or higher) (ELEMENTRAC CS-I, ELTRA).

[0070] c) Measurement of Porosity The porosity of the core part was derived through the following Equation 1.

Equation

[0071] In the above formula (1), the true density is 2.33 g / cc, and the total pore volume was measured using TriStar II 3020 equipment from Micrometrics. Also, the total pore volume was measured through the amount of nitrogen gas adsorbed due to the change in relative pressure at liquid nitrogen temperature (77K).

[0072] d) Measurement of the number density of silicon carbide (SiC) particles The silicon carbide particles in the negative electrode active material shell part manufactured in the above Embodiments 1 to 3 and Comparative Examples 4 to 6 were measured.

[0073] In this measurement, the cross-section of the powder was processed using a Focused-ion beam (FIB) and observed and measured via FE-SEM.

[0074] e) Measurement of the amount of oxygen The negative electrode active material was measured via quantification of the gas generated by combustion at a high temperature (3000 °C or higher) (836 Series, LECO).

[0075] f) Measurement of crystal grains (XRD) The Cu-Kα line was scanned on the sample powder pellet to be measured by an XRD (X’pert, Malvern Panalytical) instrument to analyze the crystal structure. Here, the size of the observed crystal grains was calculated via the following formula.

Equation

[0076] The powder electrical conductivity of the negative electrode active materials manufactured in the above Embodiments 1 to 3 and Comparative Examples 1 to 6 was measured.

[0077] In this measurement, the powder was pelletized, and the electrical conductivity of the powder was measured based on the 4-probe measurement method. After loading 500 g of each negative electrode active material powder into the powder resistance measurement container, the generated electrical resistance was measured and converted into electrical conductivity. Here, the electrical resistance was measured in real time while compressing the powder pellet.

[0078] The measurement results thereof are summarized and shown in Table 1 below.

[0079]

Table 1

[0080] (3) Manufacture of coin cells a) Manufacture of coin half-cells The negative electrode active material, conductive material (Super P), and binder (SBR-CMC) manufactured according to the above Embodiments 1 to 3 and Comparative Examples 1 to 6 were uniformly mixed at a weight ratio of 94:2:4 to prepare a negative electrode slurry. The negative electrode slurry was coated on a copper thin film current collector with a thickness of 10 μm, and the coated electrode was dried at 120°C for 20 minutes and then rolled (pressing) to manufacture a negative electrode.

[0081] Using the negative electrode and metallic lithium as the counter electrode, a polyethylene (PE) separator as the separator, and an electrolyte prepared by dissolving 1.0 M LiPF6 in a solvent mixed at a volume ratio of ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) = 3:5:2, a CR2032 type coin half-cell was manufactured.

[0082] b) Manufacture of coin full-cells Using the same negative electrode used in the coin half-cell, the positive electrode was manufactured as follows.

[0083] As the positive electrode active material, LiNi 0.6 Co 0.2 Mn 0.2 O2, conductive material (Super P), and binder (PVDF) were mixed at a weight ratio of 95:2:3 to prepare a positive electrode slurry. Then, the positive electrode slurry was coated on an aluminum foil current collector with a thickness of 12 μm, and the coated electrode plate was dried at 120°C for 15 minutes and rolled (pressing) to manufacture a positive electrode.

[0084] Using the manufactured positive and negative electrodes, a PE separator membrane as the separator membrane, and a mixture of 1.5 M LiPF6 dissolved in a mixed solvent with a volume ratio of EC:DEC:DMC = 2:1:7 + 5% fluoroethylene carbonate (FEC), a CR2032 type coin full cell was manufactured.

[0085] (3) Electrochemical evaluation method (Table 2) a) Coin half cell The coin half cells manufactured using the negative electrode active materials manufactured in Embodiments 1 to 3 and Comparative Examples 1 to 6 according to the present invention were each charged at a constant current of 0.1C rate at 25°C until the voltage reached 0.01V (vs. Li), and then charged at a constant voltage until the current reached 0.05C while maintaining 0.01V. After the charged cells were rested for 10 minutes, they were discharged at a constant current of 0.1C until the voltage reached 1.5V (vs. Li) during discharge (performed 2 times, initial formation).

[0086] On the other hand, the "C" means a value obtained by dividing the total capacity of the cell by the total discharge time as the discharge rate of the cell.

[0087] The initial charge capacity and the initial discharge capacity are the charge and discharge capacities in the first cycle, which were calculated from the following formula. Initial efficiency [%] = (discharge capacity of the first cycle / charge capacity of the first cycle) × 100

[0088] b) Coin full cell The coin full cells manufactured using the negative electrode active materials manufactured in Embodiments 1 to 3 and Comparative Examples 1 to 6 were each charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.2V, and then charged at a constant voltage until the current reached 0.05C while maintaining 4.2V. After the charged cells were rested for 10 minutes, they were discharged at a constant current of 0.1C until the voltage reached 2.7V during discharge (performed 2 times, initial formation).

[0089] Thereafter, the cell was charged at a constant current of 1.0 C rate at 25 °C until the voltage reached 4.2 V, and then charged at a constant voltage while maintaining 4.2 V until the current reached 0.05 C. After allowing the charged coin cell to rest for 10 minutes, the cycle of discharging at a constant current of 1.0 C until the voltage reached 2.7 V during discharge was repeated (cycles 1 to 100).

[0090] The life characteristics were calculated from the following formula, and the results are shown in Table 2 and Figure 2 below. Lifetime characteristics [%] = (discharge capacity of the 100th cycle / discharge capacity of the first cycle) × 100

[0091] The measured output characteristics of the cells using the negative electrode active materials manufactured according to Embodiments 1 to 3 and Comparative Examples 1 to 6 were calculated from the following formula, and the results are shown in Table 2 and Figure 3 below. Output characteristics [%] = (discharge capacity at 5.0C / discharge capacity at 0.1C) × 100

[0092] The measured electrical resistance (DCIR) of the cells using the negative electrode active materials manufactured according to Embodiments 1 to 3 and Comparative Examples 1 to 6 was calculated from the following formula, and measured through the ratio of the voltage and current change values in the equilibrium state (0) and the current application state (a) by the following formula. DC - iR [%] = [(V a -V 0 ) / (I a -I 0 )] = [△V / △I]

[0093] The results are shown in Table 2 below.

[0094]

Table 2

[0095] As a result, in the cases of Embodiments 1 to 3 including the negative electrode active material according to one embodiment of the present invention, the life characteristics and output characteristics are superior compared to Comparative Examples 1 to 3 including single silicon particle cores, and the SiC particle density is 50 to 100 / μm 2 It is confirmed that it is better in terms of life characteristics compared to Comparative Examples 4 to 5 where the range is exceeded and Comparative Example 6 where SiC is not formed.

[0096] On the other hand, in the cases of Comparative Examples 1 to 3, the DC-iR value was measured to be low and the electric conductivity was shown to be high. However, as described above, in Comparative Examples 1 to 3, the structure of the material is disadvantageous for durability and shows inferior results in terms of life / output, etc.

[0097] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and those having ordinary knowledge in the technical field can apply various technical modifications and deformations based on the above. For example, the described technology may be executed in a different order from the described method, and / or the described components may be combined or combined in a different form from the described method, or may be replaced or substituted by other components or equivalents, and appropriate results can be achieved.

[0098] Therefore, other realizations, other embodiments, and equivalents to the claims will also fall within the scope of the claims described below.

Description of Reference Numerals

[0099] 10: Silicon carbide (SiC) particles 20: Silicon nanoparticles 30: Carbon-based shell layer

Claims

1. a core containing metal particles, a shell layer formed outside the core, and the shell layer contains metal carbide particles and a carbonaceous material, the metal particles contained in the core include at least one silicon particle selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles, the metal carbide particles contained in the shell layer are silicon carbide (SiC) particles, The number density (number / μm ２ ) within the shell layer of the metal carbide particles is 50 or more and 100 or less, and the negative electrode active material is characterized by this.

2. The average particle size of the silicon nanoparticles is D ５０ The negative electrode active material according to claim 1, wherein the standard is 80 nm to 130 nm.

3. The size of the silicon carbide is 50 nm to 200 nm. The negative electrode active material according to Claim 1.

4. The carbonaceous material contains one or more of crystalline and amorphous carbon. The negative electrode active material according to Claim 1.

5. The crystalline carbon contains graphite-based carbon. The negative electrode active material according to Claim 4.

6. The amorphous carbon is made of one or more selected from the group consisting of sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin, or vinyl chloride resin, coal-based pitch, petroleum-based pitch, polyvinyl chloride, mesophase pitch, tar, block-copolymer, polyol, and low molecular weight medium oil. The negative electrode active material according to Claim 4.

7. The average particle size (D ５０ ) of the core-shell structure is 3 μm to 10 μm, The thickness of the shell layer is 100 nm to 3 μm. The negative electrode active material according to Claim 1.

8. The core additionally contains one or more of crystalline carbon and amorphous carbon. The negative electrode active material according to Claim 1.

9. a step (S1) of dispersing metal nanoparticles in a solvent, a step (S2) of spray-drying the dispersed solution to produce spherical metal precursor powder, a step (S3) of mixing the spherical metal precursor powder with an amorphous carbon precursor and crystalline carbon to form a composite, a step (S4) of heat-treating at 1100°C to 1400°C for 3 hours to 8 hours, and The method for manufacturing a negative electrode active material according to claim 1, wherein the metal nanoparticles contain at least one silicon particle selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles.

10. The manufacturing method according to claim 9, wherein the solvent is a solvent containing one or more selected from the group consisting of methanol, ethanol, propanol, and butanol.

11. The crystalline carbon contains graphite-based carbon, The amorphous carbon is formed from one or more selected from the group consisting of sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin, or vinyl chloride resin, coal-based pitch, petroleum-based pitch, polyvinyl chloride, mesophase pitch, tar, block-copolymer, polyol, and low molecular weight medium oil. The manufacturing method according to claim 9.

12. The manufacturing method according to claim 9, wherein the mixing weight ratio of the spherical metal precursor powder and the amorphous carbon precursor in the step (S3) is 40:20 to 40:

35.

13. A lithium secondary battery containing the negative electrode active material according to any one of claims 1 to 8.

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