Composite particle, method for manufacturing composite particle, and secondary battery

Abstract

The present invention relates to a composite particle, a method for manufacturing the composite particle, and an application thereof. The composite particle is a particle which can solve a volume expansion problem of a conventional silicon-based negative electrode active material and maintain excellent structural stability under repetitive charge and discharge conditions of a battery, the composite particle comprising: a core particle; a first coating layer surrounding at least a portion of an inner surface of the core particle and an outer surface of the core particle; and a second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and a surface of the first coating layer, wherein the core particle includes a crystalline silicon (c-Si) component, the first coating layer includes an amorphous silicon (a-Ci) component, and the second coating layer includes a carbon component.

Description

Composite particles, method for manufacturing composite particles, and secondary batteries

[0001] The present invention relates to a composite particle comprising two or more components, a method for manufacturing the composite particle, and a secondary battery in which the composite particle is applied as an electrode active material.

[0002] Rechargeable batteries are devices that store and supply electrical energy by repeating the process of being charged by an external power source and discharged when needed. They play a key role across various industries, including not only portable electronic devices but also electric vehicles (EVs), hybrid vehicles (HEVs), and energy storage systems (ESS). The performance and reliability of these rechargeable batteries are determined by the physical and chemical properties of the active materials used in the electrodes; in particular, the negative electrode active material has a direct impact on the battery's energy density, output characteristics, fast charging characteristics, and lifespan characteristics. Currently, graphite-based materials are mainly used as negative electrodes in commercially available lithium-ion batteries, but there is a limitation in that it is difficult to meet the demands of next-generation high-capacity batteries as the theoretical capacity of graphite is only about 300–400 mAh / g.

[0003] As an alternative, silicon-based active materials with a high theoretical capacity (approx. 4,000–4,500 mAh / g) are gaining attention. Silicon is suitable as a high-energy-density anode material because it offers storage capacity comparable to lithium metal while maintaining relatively excellent safety. However, silicon undergoes extreme volume expansion of more than 300 percent during the insertion and extraction of lithium, leading to rapid degradation of cycle performance due to particle cracking, delamination, electrode structure collapse, reduced electrical conductivity, and the repeated formation and decomposition of the solid electrolyte interface (SEI) layer. Unless these structural instability and mechanical and / or electrical degradation of the electrode material are resolved, it is difficult to commercialize silicon-only anode materials.

[0004] As a technical approach to overcome this, silicon-based composite particles, formed by combining silicon with carbon, metal oxides, metal silicides, polymer binders, or conductive additives, are being actively developed. Silicon-based composite particles can alleviate mechanical stress caused by volume changes in silicon, enhance electron-ion conductivity through various conductive matrices or surface coatings, and ensure structural and electrochemical stability by inducing the formation of a stable SEI layer. Such composite particle structures enable the realization of cathode active materials that exhibit excellent long lifespan, high-rate performance, and cyclic charge-discharge stability while maintaining the high-capacity characteristics of silicon.

[0005] Therefore, silicon-based composite particles are evaluated as a key next-generation material capable of fundamentally overcoming the capacity limitations of existing graphite-based anode active materials, and their importance is growing further due to the expansion of the electric vehicle industry and the increasing demand for high-output, high-energy storage systems. In the future, silicon-based anode material technology will become an essential element for the development of high-performance secondary batteries, and accordingly, continuous research on manufacturing technology, structural optimization, and electrode design technology for silicon-based composite particles is required.

[0006] One embodiment of the present invention aims to solve the problem in which the volume of silicon particles in conventional silicon-based negative electrode active materials rapidly expands and contracts due to lithium insertion and / or extraction during the charge-discharge process, resulting in cracking of the electrode structure, collapse of the conductive network, electrode delamination, and degradation of lifespan. By introducing specific physical and chemical structures into silicon-based particles, the invention aims to provide a negative electrode active material capable of mitigating mechanical stress caused by volume changes and maintaining structural stability even under repeated charge-discharge conditions.

[0007] Another embodiment of the present invention aims to provide a method for manufacturing silicon-based particles of a specific physical and chemical structure to improve the problems of capacity degradation and lifespan reduction that occur during actual application despite the high theoretical capacity of silicon. This method is an efficient process means for manufacturing silicon-based particles suitable for application as a negative electrode active material, which possess low expansion characteristics that significantly reduce the expansion rate while maintaining high capacity characteristics.

[0008] Another embodiment of the present invention aims to provide a secondary battery in which the problem of rapidly degrading electrochemical performance due to the formation of an unstable solid electrolyte interface (SEI) and reduced conductivity observed in conventional silicon-based negative electrode active materials is resolved when the silicon-based particles are applied as a negative electrode active material.

[0009] In one embodiment of the present invention, a composite particle is provided comprising: a core particle; a first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and a second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer; wherein the core particle comprises a crystalline silicon (c-Si) component, the first coating layer comprises an amorphous silicon (a-Ci) component, and the second coating layer comprises a carbon component.

[0010] In the composite particles according to one embodiment, the content of amorphous silicon (a-Si) may be about 5 parts by weight or more and about 35 parts by weight or less relative to 100 parts by weight of crystalline silicon (c-Si).

[0011] In one embodiment, the core particles may further include graphite.

[0012] In the composite particles according to one embodiment, the content of the graphite may be about 5 parts by weight or more and about 35 parts by weight or less relative to 100 parts by weight of the crystalline silicon (c-Si).

[0013] In the composite particle according to one embodiment, the following [Formula 1] may be greater than about 1.5% and less than or equal to about 15.0%.

[0014] [Formula 1]

[0015]

[0016] In the above [Equation 1], Lc is the particle size (D50) at the 50 volume% point of the cumulative distribution of the core particles, and Lt is the particle size (D50) at the 50 volume% point of the cumulative distribution of the composite particles.

[0017] In one embodiment, the particle size (D50) at the 50 volume% point of the cumulative distribution of the composite particles may be about 15㎛ or more and about 25㎛ or less.

[0018] In another embodiment of the present invention, a method for manufacturing a composite particle is provided, comprising: a step of preparing a first raw material composition containing a crystalline silicon (c-Si) providing component; a step of manufacturing a core particle containing crystalline silicon (c-Si) by processing the first raw material composition by a spray drying method; a step of preparing a second raw material composition containing an amorphous silicon (a-Si) providing component; a step of manufacturing a first coating layer containing amorphous silicon (a-Si) by processing the second raw material composition by a chemical vapor deposition (CVD) method, which surrounds at least a portion of the inner surface of the core particle and the outer surface of the core particle; a step of preparing a third raw material composition containing a carbon providing component; and a step of manufacturing a second coating layer containing a carbon component from the third raw material composition, which surrounds at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer.

[0019] In one embodiment, the crystalline silicon (c-Si) providing component comprises silicon particles, and the average particle size of the silicon particles may be about 40 nm or more and about 100 nm or less.

[0020] In one embodiment, the first raw material composition comprises a dispersion of the silica particles, and the solid content in the dispersion of the silica particles may be about 3% by weight or more and about 15% by weight or less.

[0021] In one embodiment, the first raw material composition may further include graphite.

[0022] In one embodiment, the spray drying method can be performed under conditions where the inflow rate of the first raw material composition is about 100 mL / min or more and about 500 mL / min or less.

[0023] In one embodiment, the amorphous silicon (a-Si) providing component may include one selected from the group consisting of hydrosilane, silazane, aminosilane, silicon halides, organosilicon compounds, and combinations thereof.

[0024] In one embodiment, the content of the amorphous silicon (a-Si) providing component in the second raw material composition may be about 99 volume% or more and about 100 volume% or less.

[0025] In one embodiment, the carbon-providing component is acetylene (C2H2), ethylene (C2H4), ethane (C2H6), propene (C3H6), butadiene (C4H6), methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H 10 It may include one selected from the group consisting of ), benzene (C6H6), toluene, tar, phenol, phenolic resin, polyacrylonitrile (PAN), pitch, and combinations thereof.

[0026] In one embodiment, the third raw material composition may contain the carbon-providing component in an amount of about 5 volume% or more and about 15 volume% or less.

[0027] In another embodiment, the present invention provides a secondary battery comprising: a cathode including a cathode active material layer and a cathode current collector; an anode including an anode active material layer and an anode current collector; and an electrolyte disposed between the cathode and the anode; wherein the cathode active material layer comprises a cathode active material, and the cathode active material comprises a composite particle, and the composite particle comprises a core particle; a first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and a second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer; wherein the core particle comprises a crystalline silicon (c-Si) component, the first coating layer comprises an amorphous silicon (a-Si) component, and the second coating layer comprises a carbon component.

[0028] The above composite particles introduce a dual structure of crystalline silicon and amorphous silicon and carbon composites, thereby mitigating mechanical stress due to volume change compared to conventional silicon-based negative electrode active materials when applied as a negative electrode active material, so that a battery incorporating the above composite particles can maintain excellent structural stability even under repeated charge and discharge conditions.

[0029] The method for manufacturing the above composite particles can produce the composite particles having optimal physical structure and chemical properties through efficient process means, thereby providing a negative electrode active material with low expansion characteristics in which the expansion rate is significantly reduced while maintaining high capacity characteristics.

[0030] The above secondary battery applies the above composite particles to the negative electrode active material, thereby solving the problems of unstable solid electrolyte interface (SEI) formation and reduced electrical conductivity observed in conventional silicon-based active materials, and enabling the realization of technical advantages in which excellent electrochemical performance is maintained for a long time even under repeated charge and discharge conditions.

[0031] FIG. 1 schematically illustrates the cross-sectional structure of the composite particle according to one embodiment.

[0032] FIG. 2 schematically illustrates the process flowchart of the method for manufacturing the composite particles according to one embodiment and the cross-sectional structure of the product of each process.

[0033] FIG. 3 schematically illustrates the cross-sectional structure of the secondary battery according to one embodiment.

[0034] Figure 4 shows the results of the analysis of the energy dispersive spectral (EDS) component distribution of the example and comparative example according to Evaluation Example 1.

[0035] Figure 5 shows the results of Raman spectroscopic analysis of the example and comparative example according to Evaluation Example 2.

[0036] Figure 6 shows the evaluation results of the battery capacity retention rate of the example and comparative example according to Evaluation Example 3.

[0037] The present invention may relate to a composite particle comprising: a core particle; a first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and a second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer, wherein the core particle comprises a crystalline silicon (c-Si) component, the first coating layer comprises an amorphous silicon (a-Ci) component, and the second coating layer comprises a carbon component.

[0038] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments or examples described below. However, the present invention is not limited to the embodiments or examples disclosed below but may be implemented in various different forms. The embodiments or examples specified below are provided merely to ensure that the disclosure of the present invention is complete and to inform those skilled in the art of the scope of the invention, and the scope of the rights of the present invention is defined by the scope of the claims.

[0039] In the drawings, the thickness of some components has been enlarged as necessary to clearly represent layers or regions. Additionally, in the drawings, the thickness of some layers and regions has been exaggerated for convenience of explanation. Throughout the specification, the same reference numerals refer to the same components.

[0040] Unless otherwise specifically defined, terms used in this specification and claims shall be interpreted in the sense generally understood by those skilled in the art to which the present invention pertains.

[0041] In the present specification and claims, if one component or step is described as 'includes,' 'composes,' 'has,' etc., another component or step, or if one component or step is described as 'consists of,' etc., another component or step may be included unless there is a limitation of 'only.'

[0042] Where a component is expressed in the singular in this specification and claims, it shall be interpreted to encompass multiple cases unless otherwise stated that it is interpreted only in the singular.

[0043] Where in this specification and claims, if one step or method is described as 'after,' 'followed,' 'next,' 'before,' etc., of / with another step or method, unless 'immediately' or 'directly' is specified, it shall be interpreted to include not only cases where the two steps or methods are consecutive but also cases where they are not consecutive.

[0044] In describing numerical ranges in this specification and claims, when expressed as 'X to Y', 'X or greater', or 'X or less', it shall be interpreted to include all numbers between X and Y, including the numerical values ​​X and Y. Furthermore, unless otherwise explicitly stated, it shall be interpreted to include a margin of error.

[0045] In describing a configuration in this specification and claims, when modified by terms such as 'first,' 'second,' etc., these terms function merely as modifiers to identify mutually distinct configurations and are not to be interpreted as limiting a numerical order or priority.

[0046] Hereinafter, embodiments according to the present invention will be described in detail.

[0047]

[0048] [Composite Particle]

[0049] In one embodiment of the present invention, a composite particle is provided comprising: a core particle; a first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and a second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer; wherein the core particle comprises a crystalline silicon (c-Si) component, the first coating layer comprises an amorphous silicon (a-Ci) component, and the second coating layer comprises a carbon component.

[0050] FIG. 1 schematically illustrates a cross-sectional view of the composite particle (100) according to one embodiment.

[0051] Referring to FIG. 1, the composite particle (100) may include the core particle (10) and may include a first coating layer (21) that surrounds at least a portion of the inner surface and outer surface of the core particle (10). Additionally, the composite particle (100) may include the second coating layer (22), and the second coating layer (22) may have a structure that surrounds at least a portion of the inner surface, outer surface of the core particle (10), and the surface of the first coating layer (21).

[0052] In one embodiment, the composite particle (100) can be applied as an electrode active material of a secondary battery. Specifically, the composite particle (100) can be applied as a negative electrode active material.

[0053] In one embodiment, the core particle (10) may include an internal pore. Specifically, the internal pore may include an open internal pore connected to the outside of the core particle (10). By including such a pore structure in the core particle (10), when the composite particle (100) is applied as an electrode active material, the stress buffering effect against volume expansion can be improved, and it can contribute to the formation of a stable solid electrolyte interface layer (SEI). In addition, the open internal pore improves electrolyte accessibility, thereby providing a structure advantageous for high-efficiency charging and discharging.

[0054] In one embodiment, the porosity of the core particle (10) may be about 20 volume% or more and about 40 volume% or less. By satisfying this range, the volume expansion buffering effect caused by the internal porosity can be maximized, and the weight relative to the amount of the core particle (10) used can be reduced, which may be more advantageous in terms of high capacity design and lightweighting based on the same volume.

[0055] In one embodiment, the core particle (10) may include crystalline silicon (c-Si). The crystalline silicon (c-Si) is a silicon material having a regular crystal lattice structure. Since the core particle (10) includes the crystalline silicon (c-Si), it may be more advantageous in terms of having high electron mobility and excellent mechanical strength due to its crystal structure, and in securing a stable structure maintenance function during electrochemical reactions.

[0056] In one embodiment, the content of the crystalline silicon (c-Si) in the entire composite particle (100) may be about 50 wt% or more, for example, greater than about 50 wt%, greater than about 55 wt%, greater than about 60 wt%, or greater than about 60 wt%. Additionally, the content of the crystalline silicon (c-Si) in the entire composite particle (100) may be about 90 wt% or less, for example, less than about 90 wt%, less than about 85 wt%, less than about 80 wt%, less than about 75 wt%, less than about 70 wt%, less than about 70 wt%, or less than about 69 wt%.

[0057] In one embodiment, the crystalline silicon (c-Si) derived component may include silicon particles. Specifically, the core particle (10) may include the crystalline silicon (c-Si) as a spray-dried processing product of a solution in which the silicon particles are dispersed. Since the crystalline silicon (c-Si) is derived from a raw material component in the form of particles, it may be more advantageous to maximize the technical effect attributed to the crystalline silicon (c-Si) by harmonizing with the physical structure and arrangement characteristics of the core particle (10) within the composite particle (100). Furthermore, since the crystalline silicon (c-Si) is derived from a spray-dried processing product of a solution in which the silicon particles are dispersed, it may be more advantageous in that the physical and chemical properties of the core particle (10) are formed in a way that is favorable for realizing the technical effect of the composite particle (100) to the intended level, compared to cases by other processing methods.

[0058] In one embodiment, the silicon particles, which are the crystalline silicon (c-Si) derived components, may have an average particle size of about 40 nm or more, for example, about 45 nm or more, about 50 nm or more, about 55 nm or more, about 60 nm or more, or about 65 nm or more. Additionally, the silicon particles may have an average particle size of less than about 100 nm, for example, about 95 nm or less, about 90 nm or less, about 85 nm or less, about 80 nm or less, or about 75 nm or less. In this specification, the 'average particle size' refers to the crystal grain size of the silicon primary particles and can be calculated by applying a Scherrer analysis method based on the Full Width at Half Maximum (FWHM) of the peak diffraction pattern obtained using X-ray diffraction (XRD) equipment. The above XRD measurement can be performed using Cu Kα (λ = 1.5406 Å) as a light source and under scan conditions of 0.02 degree (°) step and 1 degree (°) / min in the range of 2θ = 20 degrees (°) to 80 degrees (°), and the grain size calculated by substituting the corrected full width at half maximum values ​​of the obtained diffraction peaks (e.g., (111), (220), (311) reflection planes) into the Scherrer equation can be used as the average grain size.

[0059] In one embodiment, the core particle (10) may further include graphite. When the core particle (10) uses graphite mixed with crystalline silicon (c-Si), the graphite disperses the volume expansion stress during charging and discharging of the crystalline silicon (c-Si), thereby suppressing fracture and the collapse of the conductive path, and can improve electrical conductivity which is insufficient with the crystalline silicon (c-Si) alone, improve initial Coulomb efficiency, and improve the processability of the active material slurry.

[0060] In one embodiment, the graphite may include one selected from the group consisting of natural graphite, synthetic graphite, and combinations thereof. Additionally, in terms of shape, the graphite may include one selected from the group consisting of flake graphite, spherical graphite, and combinations thereof.

[0061] In one embodiment, the core particle (10) may contain about 0 parts by weight or more of the graphite relative to 100 parts by weight of the crystalline silicon (c-Si), for example, more than about 0 parts by weight, about 1 part by weight or more, about 5 parts by weight or more, about 6 parts by weight or more, about 7 parts by weight or more, about 8 parts by weight or more, about 9 parts by weight or more, about 10 parts by weight or more, about 11 parts by weight or more, about 12 parts by weight or more, about 13 parts by weight or more, about 14 parts by weight or more, about 15 parts by weight or more, about 16 parts by weight or more, about 17 parts by weight or more, about 18 parts by weight or more, about 19 parts by weight or more, or about 20 parts by weight or more. Additionally, the core particle (10) may contain about 35 parts by weight or less of the graphite relative to 100 parts by weight of the crystalline silicon (c-Si), for example, less than about 35 parts by weight. By satisfying the relative content ratio of the graphite relative to the crystalline silicon (c-Si) in this range, the high capacity characteristics and volume expansion mitigation characteristics of the core particles (10) are appropriately balanced, making it more advantageous to achieve excellent electrical conductivity and cell efficiency.

[0062] In one embodiment, the graphite in the core particle (10) has a specific surface area (based on the BET method) of about 1 m² 2 It can be more than / g, for example, about 1.5 m 2 / g or more, about 2 m2 / g or more, approximately 2.5 m 2 / g or more, about 3 m 2 / g or more, or about 3.5 m 2 It may be greater than / g. In addition, the graphite has a specific surface area of ​​approximately 15 m² 2 It can be less than / g, for example, about 14.5 m 2 / g or less, approximately 14 m 2 / g or less, approx. 13.5 m 2 / g or less, approximately 13 m 2 / g or less, approximately 12.5 m 2 / g or less, approximately 12 m 2 / g or less, approx. 11.5 m 2 / g or less, or about 10 m 2 It may be less than / g.

[0063] Referring to FIG. 1, the first coating layer (21) may have a structure that surrounds at least a portion of the outer surface of the core particle (10); a structure that surrounds at least a portion of the inner surface of the core particle (10); or a structure corresponding to both of these. By having such a relative arrangement relationship between the core particle (10) and the first coating layer (21), the volume expansion buffering effect of the composite particle (100) can be further enhanced.

[0064] In one embodiment, the first coating layer (21) may include amorphous silicon (a-Si). The crystalline silicon (c-Si) in the core particles (10) is a silicon material having a regular crystal lattice structure, and due to its crystal structure, it has high electron mobility and excellent mechanical strength, and may be more advantageous in terms of securing a stable structure maintenance function during electrochemical reactions. However, the fixed lattice spacing of the crystalline silicon (c-Si) may rapidly expand due to the insertion and extraction of ions during the charging and discharging process, causing a volume change of about 300% or more, and consequently, there is a risk that particle cracking, electrode fracture, and collapse of the conductive path may occur. At this time, since the first coating layer (21) surrounding at least a portion of the outer surface and inner surface of the core particle (10) includes amorphous silicon (a-Si), it can be flexibly deformed in response to external stress during the charging and discharging process due to the irregular atomic arrangement of the amorphous silicon (a-Si), thereby effectively absorbing volume changes and suppressing crack formation.

[0065] Accordingly, the composite particle (100) simultaneously secures high capacity characteristics and expansion absorption characteristics through a composite structure of the core particle (10) based on crystalline silicon (c-Si) and the first coating layer (21) based on amorphous silicon (a-Si), so when applied as a negative electrode active material, it may be more advantageous to maintain structural stability during the charge-discharge cycle of the battery and significantly suppress the degradation of the active material's performance.

[0066] In one embodiment, the composite particle (100) may have an amorphous silicon (a-Si) content of about 5 parts by weight or more relative to 100 parts by weight of crystalline silicon (c-Si), for example, about 5.5 parts by weight or more, about 6 parts by weight or more, about 6.5 parts by weight or more, or about 7 parts by weight or more. Additionally, the amorphous silicon (a-Si) content may be about 35 parts by weight or less relative to 100 parts by weight of crystalline silicon (c-Si), for example, 30 parts by weight or less, or about 25 parts by weight or less. By satisfying the aforementioned ranges for the relative content ratio of crystalline silicon (c-Si) and amorphous silicon (a-Si) in the composite particle (100), it may be more advantageous to simultaneously achieve high capacity characteristics and volume expansion absorption characteristics.

[0067] In one embodiment, the amorphous silicon (a-Si) derived component may include one selected from the group consisting of hydrosilane, silazane, aminosilane, silicon halides, organosilicon compounds, and combinations thereof. Specifically, the first coating layer (21) may include the amorphous silicon (a-Si) as a thermochemical vapor deposition (CVD) processing product of the amorphous silicon (a-Si) derived component. Since the amorphous silicon (a-Si) is derived from the aforementioned types of components, it may be more advantageous to realize a volume expansion buffering effect through the dual structure of the core particle (10) and the first coating layer (21). In addition, since the amorphous silicon (a-Si) is derived from a thermochemical vapor deposition (CVD) processing product, the adhesion between the core particles (10) and the first coating layer (21) can be further improved compared to other processing methods, and it may be more advantageous to realize the technical effect of the composite structure at the intended level.

[0068] In one embodiment, the hydrogenated silane may include one selected from the group consisting of, for example, silane (SiH4), disilane (Si2H6), trisilane (Si3H8), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2) and combinations thereof.

[0069] In one embodiment, the silazane may include one selected from the group consisting of, for example, ethyl disilazane, hexamethyldisilazane, polysilazane (PSZ), and combinations thereof.

[0070] In one embodiment, the aminosilane may comprise, for example, one selected from the group consisting of 3-aminopropyltriethoxysilane (3-Aminopropyltriethoxysilane, APTES), 3-aminopropyltrimethoxysilane (3-Aminopropyltrimethoxysilane, APTMS), dimethylaminosilane, N-methylaminosilane, N-ethylaminosilane, bis(3-trimethoxysilylpropyl)amine, N-aminoethyl-aminopropyltriethoxysilane (AEAPTES), N-aminoethyl-aminopropyltrimethoxysilane (AEAPTMS), and combinations thereof.

[0071] The above silicon halide may include, for example, one selected from the group consisting of silicon tetrachloride (SiCl4), trichlorosilane (SiHCl3), dichlorosilane (SiH2Cl2), monochlorosilane (SiH3Cl), silicon tetrabromide (SiBr4), tribromosilane (SiHBr3), silicon tetrafluoride (SiF4), trichlorosilane (SiHF3), silicon tetraiodide (SiI4), triiodosilane (SiHI3), and combinations thereof.

[0072] In one embodiment, the organosilicon compound may include one selected from the group consisting of, for example, tetraethoxysilane (TEOS), hexamethyldisilane (HMDS), polydimethylsiloxane (PDMS) and combinations thereof.

[0073] Referring to FIG. 1, in one embodiment, the second coating layer (22) may have a structure that surrounds at least a portion of the outer surface of the core particle (10); a structure that surrounds at least a portion of the inner surface of the core particle (10); a structure that surrounds at least a portion of the surface of the first coating layer (21); or a structure corresponding to at least two or more of these structures.

[0074] In one embodiment, the second coating layer (22) may essentially include a structure that surrounds at least a portion of the surface of the first coating layer (21). The volume expansion buffering effect can be further enhanced by the composite particle (100) including a multi-stage coating structure of the first coating layer (21) and the second coating layer (22), more specifically, a double coating structure.

[0075] In one embodiment, the second coating layer (22) may include a carbon component. By including the carbon component, the second coating layer (22) can significantly improve electrical conductivity, thereby stably securing the electron transport path within the electrode and ensuring that electrochemical reactions proceed smoothly even during repeated charging and discharging, which may be more advantageous in terms of improving output characteristics. Additionally, the second coating layer (22) can improve hydrophobicity, adsorption, and dispersibility, thereby suppressing particle aggregation during the preparation of active material slurries and improving applicability to the electrode manufacturing process.

[0076] In one embodiment, the composite particle (100) may contain about 1 part by weight or more of the carbon component relative to 100 parts by weight of the crystalline silicon (c-Si), for example, about 1.5 parts by weight or more, about 2 parts by weight or more, about 2.5 parts by weight or more, about 3 parts by weight or more, about 3.5 parts by weight or more, about 4 parts by weight or more, about 4.5 parts by weight or more, about 5 parts by weight or more, about 5.5 parts by weight or more, about 6 parts by weight or more, about 6.5 parts by weight or more, about 7 parts by weight or more, or about 7.5 parts by weight or more. Additionally, the composite particle (100) may contain about 20 parts by weight or less of the carbon component relative to 100 parts by weight of the crystalline silicon (c-Si), for example, less than about 20 parts by weight, about 19 parts by weight or less, about 18 parts by weight or less, about 17 parts by weight or less, about 16 parts by weight or less, about 15 parts by weight or less, about 14 parts by weight or less, about 13 parts by weight or less, about 12 parts by weight or less, about 11 parts by weight or less, about 10 parts by weight or less, or less than about 10 parts by weight.

[0077] In one embodiment, the carbon component may include one selected from the group consisting of amorphous carbon, low-crystalline carbon, pyrolytic carbon, and combinations thereof.

[0078] The above amorphous carbon is a carbon material in a state that does not form a crystal lattice, and sp 2 Bonding and sp 3 It may have a form in which bonds are irregularly intermingled. The low-crystalline carbon is a carbon material having a crystal structure at an intermediate stage between the amorphous carbon and graphite, and is a partially aligned sp² 2 It may refer to carbon in which bonds exist but does not form a highly aligned hexagonal crystal structure like the graphite. The pyrolytic carbon may refer to amorphous or low-crystalline carbon formed by pyrolysis of an organic material or hydrocarbon gas containing carbon (C). Since the second coating layer (22) includes at least one of the amorphous carbon, the low-crystalline carbon, and the pyrolytic carbon as the carbon component, it is advantageous to flexibly respond to changes in the shape of the composite particle (100), and it may be more advantageous in terms of stress relief, inhibition of electrolyte penetration, and improvement of interfacial stability occurring during the formation of the solid electrolyte interface layer (SEI).

[0079] In one embodiment, the derived component of the carbon component in the second coating layer (22) may include a carbon precursor, and the carbon precursor is, for example, acetylene (C2H2), ethylene (C2H4), ethane (C2H6), propene (C3H6), butadiene (C4H6), methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H 10It may include one selected from the group consisting of ), benzene (C6H6), toluene, tar, phenol, phenolic resin, polyacrylonitrile (PAN), pitch, and combinations thereof.

[0080] By including the derived component of the second coating layer (22) as described above, it may be more advantageous to improve both the volume expansion mitigation effect and the electrical conductivity enhancement effect caused by the double coating structure of the amorphous silicon (a-Si) of the first coating layer (21) and the carbon component of the second coating layer (22) to a certain level or higher.

[0081] In one embodiment, the core particle (10) and the composite particle (100) each have an appropriate particle size, which may be more advantageous in terms of improving processability as an electrode active material and optimizing the realization of intrinsic performance.

[0082] In one embodiment, the value of [Equation 1] below may be greater than about 1.5% and less than or equal to about 15.0%.

[0083] [Formula 1]

[0084]

[0085] In the above [Equation 1], Lc is the particle size (D50) at the 50 volume% point of the cumulative distribution of the core particle (10), and Lt is the particle size (D50) at the 50 volume% point of the cumulative distribution of the composite particle (100).

[0086] In this specification, D50 refers to the particle size at the 50 volume percent point of the cumulative distribution in the corresponding particle group and can be measured by a commonly known method. For example, D50 can be measured using a laser diffraction and scattering particle size analyzer (PSA, Mastersizer 3000, Malvern Panalytical).

[0087] The above [Equation 1] represents the ratio of the size difference between the composite particle (100) and the core particle (10) relative to the total size of the composite particle (100) as a percentage, and can be understood as an indicator that quantitatively represents the ratio of the first coating layer (21) and the second coating layer (22) within the entire composite particle (100). By including the first coating layer (21) and the second coating layer (22) within the entire composite particle (100) in a ratio corresponding to the aforementioned range, it may be more advantageous for the realization of technical purposes through the two layers.

[0088] In one embodiment, the value of [Equation 1] may be greater than about 1.5%, for example, about 1.6% or more, about 1.7% or more, or about 1.8% or more. Additionally, the value of [Equation 1] may be about 15.0% or less, for example, about 14.5% or less, about 14.0% or less, about 13.5% or less, about 13.0% or less, about 12.5% ​​or less, about 12.0% or less, about 11.5% or less, about 11.0% or less, or 10.5% or less.

[0089] In one embodiment, the particle size (D50) at the 50 volume% point of the cumulative distribution of the composite particle (100), i.e., the Lt value, may be about 15 μm or more, for example, about 15.5 μm or more, about 16 μm or more, about 16.5 μm or more, or about 17 μm or more. Additionally, the Lt value may be about 25 μm or less, for example, about 24.5 μm or less, about 24 μm or less, about 23.5 μm or less, about 23 μm or less, about 22.5 μm or less, about 22 μm or less, about 21.5 μm or less, about 21 μm or less, about 20.5 μm or less, about 20 μm or less, about 19.5 μm or less, or about 19 μm or less. The overall size of the composite particle (100) satisfies this range, which may be advantageous for uniform coating without voids in the active material slurry during the process of utilizing it as an electrode active material, and the quantitative ratio of the first coating layer (21) and the second coating layer (22) satisfying [Equation 1] relative to the composite particle (100) may be more advantageous in realizing the technical effect intended by the composite particle (100).

[0090] According to one embodiment, the composite particle (100) comprises a core particle (10) containing crystalline silicon (c-Si), a first coating layer (21) containing amorphous silicon (a-Si), and a composite structure of a second coating layer (22) containing carbon components. By applying the composite particle (100) as a negative electrode active material, it is possible to effectively alleviate mechanical stress due to volume change compared to conventional silicon-based negative electrode active materials, while simultaneously realizing high capacity characteristics. This solves the problems of unstable solid electrolyte interface (SEI) formation and reduced electrical conductivity in the battery, and enables the realization of technical advantages such as maintaining excellent electrochemical performance for a long time even under repeated charge and discharge conditions.

[0091]

[0092] [Method for manufacturing composite particles]

[0093] In another embodiment of the present invention, a method for manufacturing a composite particle is provided, comprising the steps of: preparing a first raw material composition containing a crystalline silicon (c-Si) providing component; processing the first raw material composition by a spray drying method to produce a core particle containing crystalline silicon (c-Si); preparing a second raw material composition containing an amorphous silicon (a-Si) providing component; processing the second raw material composition by a chemical vapor deposition (CVD) method to produce a first coating layer containing amorphous silicon (a-Si) that surrounds at least a portion of the inner surface of the core particle and the outer surface of the core particle; preparing a third raw material composition containing a carbon providing component; and producing a second coating layer containing a carbon component from the third raw material composition that surrounds at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer.

[0094] The method for manufacturing the above composite particles is an embodiment of a method for manufacturing the above composite particles (100) according to the above-described embodiment with reference to FIG. 1, and can provide process means suitable for manufacturing the above composite particles (100) to optimally realize the above-described technical advantages.

[0095] All features of the composite particle (100) according to the embodiment described above with reference to FIG. 1 may be applied independently or in any combination in the same manner to the resulting particle produced through the method of manufacturing the composite particle, even if they are not repeatedly described in this specification, to the extent that there is no technical contradiction.

[0096] FIG. 2 schematically illustrates the process flowchart of the composite particle manufacturing method (110) according to one embodiment and the cross-sectional view of the product of each process step.

[0097] Referring to FIG. 2, the method for manufacturing the composite particle (110) comprises the step (111) of preparing a first raw material composition containing a crystalline silicon (c-Si) providing component; and the step (112) of manufacturing a core particle (10) containing crystalline silicon (c-Si) from the first raw material composition.

[0098] In one embodiment, the first raw material composition is a raw material component for manufacturing the core particle (10), and the crystalline silicon (c-Si) providing component may include silicon particles. Since the core particle (10) is manufactured from a raw material component in the form of particles, the physical structure and arrangement characteristics of the core particle (10) within the composite particle (100) and its chemical composition are appropriately harmonized, which may be more advantageous for simultaneously realizing volume expansion buffering characteristics, electrical conductivity enhancement characteristics, and high capacity retention characteristics of the composite particle (100) at a level above a certain level.

[0099] In one embodiment, the silicon particles may have an average particle size of about 40 nm or more, for example, about 45 nm or more, about 50 nm or more, about 55 nm or more, about 60 nm or more, or about 65 nm or more. Additionally, the silicon particles may have an average particle size of less than about 100 nm, for example, about 95 nm or less, about 90 nm or less, about 85 nm or less, about 80 nm or less, or about 75 nm or less.

[0100] In one embodiment, the first raw material composition may include a dispersion of the silicon particles. Specifically, the first raw material composition may include a colloidal solution in which the silicon particles are dispersed in a solvent.

[0101] In one embodiment, the dispersion of silicon particles may have a solid content of about 3 wt% or more, for example, about 3.5 wt% or more, about 4 wt% or more, about 4.5 wt% or more, about 5 wt% or more, about 5.5 wt% or more, about 6 wt% or more, about 6.5 wt% or more, about 7 wt% or more, about 7.5 wt% or more, about 8 wt% or more, or about 8.5 wt% or more. Additionally, the solid content of the silicon particle dispersion may be about 15 wt% or less, for example, about 14.5 wt% or less, about 14 wt% or less, about 13.5 wt% or less, about 13 wt% or less, about 12.5 wt% or less, about 12 wt% or less, about 11.5 wt% or less, or about 11 wt% or less. When the above solid content is satisfied, the first raw material composition containing the silica particle dispersion can secure fluidity and flowability suitable for a subsequent spray drying method, and the core particle (10) produced from the first raw material composition may have an internal pore structure having an appropriate porosity and may be more advantageous to have a physical structure suitable for forming the first coating layer (21) and the second coating layer (22) that surround at least a part of the inner and / or outer surface of the core particle (10).

[0102] In one embodiment, the silicon particle dispersion may include an organic solvent as the solvent. Specifically, the organic solvent may include, for example, one selected from the group consisting of anhydrous ethanol, methanol, 1-propanol, isopropyl alcohol (IPA), butanol, diethyl ether, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), ethyl acetate (EtOAc), methyl acetate, and combinations thereof.

[0103] In one embodiment, the first raw material composition may further include graphite. When the first raw material composition further includes graphite, the core particles (10) produced from the first raw material composition contain a mixture of graphite and crystalline silicon (c-Si). The graphite disperses the volume expansion stress during charging and discharging of the crystalline silicon (c-Si), thereby suppressing fracture and the collapse of the conductive path. Additionally, the advantages of improving electrical conductivity, which is insufficient with the crystalline silicon (c-Si) alone, improving initial Coulomb efficiency, and improving the processability of the active material slurry can be realized.

[0104] In one embodiment, the graphite may include one selected from the group consisting of natural graphite, synthetic graphite, and combinations thereof. Additionally, in terms of shape, the graphite may include one selected from the group consisting of flake graphite, spherical graphite, and combinations thereof.

[0105] In one embodiment, the graphite has a specific surface area (based on the BET method) of approximately 1 m² 2 It can be more than / g, for example, about 1.5 m 2 / g or more, about 2 m 2 / g or more, approximately 2.5 m 2 / g or more, about 3 m 2 / g or more, or about 3.5 m 2 It may be greater than / g. In addition, the graphite has a specific surface area of ​​approximately 15 m² 2 It can be less than / g, for example, about 14.5 m 2 / g or less, approximately 14 m 2 / g or less, approx. 13.5 m 2 / g or less, approximately 13 m 2 / g or less, approximately 12.5 m 2 / g or less, approximately 12 m 2 / g or less, approx. 11.5 m 2 / g or less, or about 10 m 2 It may be less than / g.

[0106] In one embodiment, the step (112) of manufacturing a core particle (10) containing crystalline silicon (c-Si) from the first raw material composition may be performed by processing the first raw material composition using a spray drying method. Since the core particle (10) is manufactured using a spray drying method, it may be more advantageous to simultaneously achieve excellent volume expansion mitigation characteristics, high capacity characteristics, and electrical conductivity enhancement characteristics in terms of physical structure and chemical properties compared to cases where it is manufactured by other process means.

[0107] In the spray drying method according to one embodiment, the inflow rate of the first raw material composition may be about 100 mL / min or more, for example, about 110 mL / min or more, about 120 mL / min or more, about 130 mL / min or more, about 140 mL / min or more, about 150 mL / min or more, about 160 mL / min or more, about 170 mL / min or more, about 180 mL / min or more, about 190 mL / min or more, about 200 mL / min or more, about 210 mL / min or more, about 220 mL / min or more, about 230 mL / min or more, about 240 mL / min or more, or about 250 mL / min or more. Additionally, the inflow rate of the first raw material composition may be about 500 mL / min or less, for example, about 480 mL / min or less, about 460 mL / min or less, about 450 mL / min or less, about 440 mL / min or less, about 420 mL / min or less, or about 400 mL / min or less. When the inflow rate of the first raw material composition satisfies such a range, the physical structure of the core particle (10) produced through the spray drying method may be advantageous in providing an internal and external surface structure suitable for subsequently forming the coating layer (20), and may be more advantageous in terms of forming the particle size of the core particle (10) uniformly.

[0108] In the spray drying method according to one embodiment, the drying temperature may be about 80°C or higher, for example, about 85°C or higher, about 90°C or higher, about 95°C or higher, or about 100°C or higher. Additionally, the drying temperature may be about 300°C or lower, for example, about 280°C or lower, about 260°C or lower, about 250°C or lower, about 240°C or lower, about 220°C or lower, or about 200°C or lower. In the spray drying method, the first raw material composition may be manufactured into the core particles (10) by drying through instantaneous heat treatment after being finely sprayed. By satisfying the drying temperature within this range, the sprayed first raw material composition may be condensed through appropriate thermal shock, and as a result, it may be advantageous for the core particles (10) to secure an appropriate pore structure and porosity.

[0109] In the spray drying method according to one embodiment, the drying time may be about 0.05 seconds or more, for example, about 0.1 seconds or more, about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 seconds or more, about 0.5 seconds or more, or about 1 second or more. Additionally, the drying time may be about 30 seconds or less, for example, about 25 seconds or less, about 20 seconds or less, about 15 seconds or less, or about 10 seconds or less. The drying time is the time for processing the sprayed first raw material composition under the drying temperature conditions, and by performing it under temperature and time conditions within this range, the physical structure and shape of the core particles (10) produced from the first raw material composition may be harmonized with the coating layer (20), making it more advantageous to realize volume expansion mitigation characteristics, electrical conductivity improvement characteristics, and high capacity characteristics.

[0110] Referring to FIG. 2, the core particles (10) are manufactured by processing the first raw material composition using a spray drying method, and the core particles (10) may include crystalline silicon (c-Si). Additionally, if the first raw material composition further includes graphite, the core particles (10) may include crystalline silicon (c-Si) and graphite.

[0111] The core particle (10) manufactured according to one embodiment may contain about 0 parts by weight or more of the graphite relative to 100 parts by weight of the crystalline silicon (c-Si), for example, more than about 0 parts by weight, about 1 part by weight or more, about 5 parts by weight or more, about 6 parts by weight or more, about 7 parts by weight or more, about 8 parts by weight or more, about 9 parts by weight or more, about 10 parts by weight or more, about 11 parts by weight or more, about 12 parts by weight or more, about 13 parts by weight or more, about 14 parts by weight or more, about 15 parts by weight or more, about 16 parts by weight or more, about 17 parts by weight or more, about 18 parts by weight or more, about 19 parts by weight or more, or about 20 parts by weight or more. In addition, the core particle (10) may contain about 35 parts by weight or less of the graphite relative to 100 parts by weight of the crystalline silicon (c-Si), for example, less than about 35 parts by weight. By satisfying this range of the relative content ratio of the graphite relative to the crystalline silicon (c-Si), the high capacity characteristics and volume expansion mitigation characteristics of the core particle (10) are appropriately balanced, making it more advantageous to achieve excellent electrical conductivity and cell efficiency.

[0112] According to one embodiment, the core particle (10) manufactured may include an internal pore. Specifically, the internal pore may include an open internal pore connected to the outside of the core particle (10). By including such a pore structure in the core particle (10), when the composite particle (100) is applied as an electrode active material, the stress buffering effect against volume expansion can be improved, and it can contribute to the formation of a stable solid electrolyte interface layer (SEI). In addition, the open internal pore improves electrolyte accessibility, thereby providing a structure advantageous for high-efficiency charging and discharging.

[0113] In one embodiment, the porosity of the core particle (10) may be about 20 volume% or more and about 40 volume% or less. By satisfying this range, the volume expansion buffering effect caused by the internal porosity can be maximized, and the weight relative to the amount of the core particle (10) used can be reduced, which may be more advantageous in terms of high capacity design and lightweighting based on the same volume.

[0114] Referring to FIG. 2, the method for manufacturing the composite particle (110) according to one embodiment may include the step (113) of preparing a second raw material composition containing an amorphous silicon (a-Si) providing component; and the step (114) of manufacturing a first coating layer (21) containing amorphous silicon (a-Si) from the second raw material composition.

[0115] The second raw material composition may include an amorphous silicon (a-Si) providing component as a raw material component for manufacturing the first coating layer (21), and the amorphous silicon (a-Si) providing component may include one selected from the group consisting of hydrosilane, silazane, aminosilane, silicon halides, organosilicon compounds and combinations thereof.

[0116] In one embodiment, the hydrogenated silane may include one selected from the group consisting of, for example, silane (SiH4), disilane (Si2H6), trisilane (Si3H8), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2) and combinations thereof.

[0117] In one embodiment, the silazane may include one selected from the group consisting of, for example, ethyl disilazane, hexamethyldisilazane, polysilazane (PSZ), and combinations thereof.

[0118] In one embodiment, the aminosilane may comprise, for example, one selected from the group consisting of 3-aminopropyltriethoxysilane (3-Aminopropyltriethoxysilane, APTES), 3-aminopropyltrimethoxysilane (3-Aminopropyltrimethoxysilane, APTMS), dimethylaminosilane, N-methylaminosilane, N-ethylaminosilane, bis(3-trimethoxysilylpropyl)amine, N-aminoethyl-aminopropyltriethoxysilane (AEAPTES), N-aminoethyl-aminopropyltrimethoxysilane (AEAPTMS), and combinations thereof.

[0119] The above silicon halide may include, for example, one selected from the group consisting of silicon tetrachloride (SiCl4), trichlorosilane (SiHCl3), dichlorosilane (SiH2Cl2), monochlorosilane (SiH3Cl), silicon tetrabromide (SiBr4), tribromosilane (SiHBr3), silicon tetrafluoride (SiF4), trichlorosilane (SiHF3), silicon tetraiodide (SiI4), triiodosilane (SiHI3), and combinations thereof.

[0120] In one embodiment, the organosilicon compound may include one selected from the group consisting of, for example, tetraethoxysilane (TEOS), hexamethyldisilane (HMDS), polydimethylsiloxane (PDMS) and combinations thereof.

[0121] In one embodiment, the content of the amorphous silicon (a-Si) providing component in the second raw material composition may be about 99 volume% or more, for example, about 99.5 volume% or more, and may also be about 100 volume% or less.

[0122] The step (114) of manufacturing the first coating layer (21) from the second raw material composition can be performed by processing using a chemical vapor deposition (CVD) method. Specifically, the second raw material composition can be processed using the chemical vapor deposition (CVD) method to manufacture the first coating layer (21) that is deposited to surround at least a portion of the inner surface of the core particle (10) and the outer surface of the core particle (10). In one embodiment, the step (114) of manufacturing the first coating layer (21) can be performed by applying a thermal chemical vapor deposition (Thermal CVD) method. By manufacturing the first coating layer (21) using such process means, the adhesion between the core particle (10) and the first coating layer (21) can be further improved compared to when other process means are applied, and it may be more advantageous to realize the technical effect of their composite structure at the intended level.

[0123] In one embodiment, the temperature at which the step of manufacturing the first coating layer (21) is performed may be about 200°C or higher, for example, about 220°C or higher, about 240°C or higher, about 250°C or higher, about 260°C or higher, about 280°C or higher, about 300°C or higher, about 320°C or higher, about 340°C or higher, about 350°C or higher, or about 400°C or higher, and may also be about 1200°C or lower, for example, about 1000°C or lower, about 950°C or lower, about 900°C or lower, about 850°C or lower, about 800°C or lower, about 750°C or lower, about 700°C or lower, about 650°C or lower, about 600°C or lower, or about 550°C or lower. When the process is carried out at the above-mentioned operating temperature, thermal decomposition from the second raw material composition is carried out with appropriate efficiency, so that the first coating layer (21) of appropriate thickness can be formed, and it may be more advantageous to form the first coating layer (21) to include amorphous silicon (a-Si) having an appropriate degree of amorphousness without hindering the technical effect of the core particle (10).

[0124] In one embodiment, the pressure at which the step of manufacturing the first coating layer (21) is performed may be about 50 kPa or more, for example, about 60 kPa or more, about 70 kPa or more, about 80 kPa or more, about 90 kPa or more, or about 100 kPa or more. Additionally, the pressure at which the performance is performed may be about 200 kPa or less, for example, about 190 kPa or less, about 180 kPa or less, about 170 kPa or less, about 160 kPa or less, about 150 kPa or less, about 140 kPa or less, about 130 kPa or less, or about 120 kPa or less. When the process is carried out at the above operating pressure, the first coating layer (21) may contain amorphous silicon (a-Si) of appropriate density and may be more advantageous for improving volume expansion buffering characteristics and high capacity characteristics together with the crystalline silicon (c-Si) of the core particle (10).

[0125] In the step of manufacturing the first coating layer (21) according to one embodiment, the time during which the process is performed under the performing temperature and the performing pressure may be about 20 minutes or more, for example, about 25 minutes or more, or about 30 minutes or more. Additionally, the time may be about 100 minutes or less, for example, about 90 minutes or less, or about 90 minutes or less. By processing the second raw material composition by the CVD method under the temperature, pressure, and time ranges, the first coating layer (21) can be deposited with an appropriate thickness on at least a portion of the inner surface or outer surface of the core particle (10), and the amorphousness and density of the amorphous silicon (a-Si) in the first coating layer (21) may be more advantageous for optimizing the effect.

[0126] Referring to FIG. 2, through the step (113) of preparing the second raw material composition and the step (114) of manufacturing the first coating layer (21), the first coating layer (21) may have a structure that surrounds at least a portion of the outer surface of the core particle (10); a structure that surrounds at least a portion of the inner surface of the core particle (10); or a structure corresponding to all of these. By manufacturing in a manner that includes the aforementioned process features, it may be more advantageous to form the core particle (10) and the first coating layer (21) to have such a relative arrangement relationship, and as a result, the volume expansion buffering effect of the finally manufactured composite particle can be further improved.

[0127] In the core particle (10) and the first coating layer (21) manufactured according to one embodiment, the content of the amorphous silicon (a-Si) in the first coating layer (21) may be about 5 parts by weight or more relative to 100 parts by weight of the crystalline silicon (c-Si) in the core particle (10), for example, about 5.5 parts by weight or more, about 6 parts by weight or more, about 6.5 parts by weight or more, or about 7 parts by weight or more. Additionally, the content of the amorphous silicon (a-Si) may be about 35 parts by weight or less relative to 100 parts by weight of the crystalline silicon (c-Si), for example, 30 parts by weight or less, or about 25 parts by weight or less. By satisfying the relative content ratio of the crystalline silicon (c-Si) and the amorphous silicon (a-Si) in the aforementioned range, the finally manufactured composite particle may be more advantageous for simultaneously achieving excellent high capacity characteristics and volume expansion absorption characteristics.

[0128] Referring to FIG. 2, the method for manufacturing the composite particle (110) may include the step (115) of preparing a third raw material composition containing a carbon-providing component; and the step of manufacturing the second coating layer (22) containing a carbon component from the third raw material composition.

[0129] The third raw material composition above may include the carbon-providing component as a raw material for manufacturing the second coating layer (22). The carbon-providing component is a precursor of the carbon component in the second coating layer (22), for example, acetylene (C2H2), ethylene (C2H4), ethane (C2H6), propene (C3H6), butadiene (C4H6), methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H 10 It may include one selected from the group consisting of benzene (C6H6), toluene, tar, phenol, phenolic resin, polyacrylonitrile (PAN), pitch, and combinations thereof. Since the third raw material composition includes such a material, it may be advantageous for the volume expansion buffering effect and electrical conductivity enhancement effect to be realized above a certain level by the multi-stage coating structure of the second coating layer (22) containing the carbon component prepared therefrom and the first coating layer (21) containing the amorphous silicon (a-Si).

[0130] In one embodiment, the third raw material composition may contain about 5 volume% or more of the carbon-providing component, for example, about 5.5 volume% or more, about 6 volume% or more, about 6.5 volume% or more, about 7 volume% or more, about 7.5 volume% or more, about 8 volume% or more, about 8.5 volume% or more, about 9 volume% or more, or about 9.5 volume% or more. Additionally, the third raw material composition may contain about 15 volume% or less of the carbon-providing component, for example, about 14.5 volume% or less, about 14 volume% or less, about 13.5 volume% or less, about 13 volume% or less, about 12.5 volume% or less, about 12 volume% or less, about 11.5 volume% or less, about 11 volume% or less, or about 10.5 volume% or less. By satisfying the content of the carbon-providing component in the third raw material composition, the carbon component in the second coating layer (22) produced therefrom may exhibit appropriate crystallinity and may be more advantageous for exhibiting excellent adhesion to the surface of the first coating layer (21) and / or the core particle (10).

[0131] In one embodiment, the third raw material composition may further include an inert gas. The inert gas may include, for example, one selected from the group consisting of nitrogen (N2), argon (Ar), helium (He), and combinations thereof. The inert gas may function as a carrier gas or transporter gas for the carbon-providing component and may serve to prevent thermal shock and local overheating during the process of manufacturing the second coating layer (22).

[0132] In one embodiment, the third raw material composition may contain about 85 volume% or more of the inert gas, for example, about 85.5 volume% or more, about 86 volume% or more, about 86.5 volume% or more, about 87 volume% or more, about 87.5 volume% or more, about 88 volume% or more, about 88.5 volume% or more, about 89 volume% or more, or about 89.5 volume% or more. Additionally, the third raw material composition may contain about 95 volume% or less of the inert gas, for example, about 94.5 volume% or less, about 94 volume% or less, about 93.5 volume% or less, about 93 volume% or less, about 92.5 volume% or less, about 92 volume% or less, or about 91.5 volume% or less.

[0133] In one embodiment, the step (116) of manufacturing the second coating layer can be performed by a process of pyrolyzing the third raw material composition.

[0134] In one embodiment, the temperature of the step (116) of manufacturing the second coating layer may be about 300°C or higher, for example, about 350°C or higher, about 400°C or higher, or about 450°C or higher. Additionally, the temperature of the step may be about 1200°C or lower, for example, about 1100°C or lower, about 1000°C or lower, about 950°C or lower, about 900°C or lower, about 850°C or lower, about 800°C or lower, about 750°C or lower, about 700°C or lower, about 650°C or lower, about 600°C or lower, or about 550°C or lower. If the temperature of the pyrolysis processing process is excessively high, the carbonization of the third raw material composition proceeds excessively, and there is a risk that the structure of the second coating layer (22) may collapse or the pore structure of the core particle (10) may be closed. That is, by performing the above pyrolysis processing at an appropriate range of operating temperatures, the second coating layer (22) may be more advantageous in having physical and chemical properties optimized for the implementation of the technical effects of the composite particle (100).

[0135] In one embodiment, the step (116) of manufacturing the second coating layer may perform constant temperature pyrolysis processing within the operating temperature range. Specifically, in the step (116) of manufacturing the second coating layer, after the process temperature range reaches the operating temperature, the third raw material composition may be carbonized by maintaining the operating temperature environment constant for a predetermined period of time.

[0136] In one embodiment, the constant temperature pyrolysis process may be performed by maintaining the operating temperature environment constant for about 10 minutes or more, for example, about 15 minutes or more, about 20 minutes or more, about 25 minutes or more, about 30 minutes or more, about 35 minutes or more, about 40 minutes or more, about 45 minutes or more, or about 50 minutes or more. Additionally, the constant temperature pyrolysis process may be performed by maintaining the operating temperature environment constant for about 150 minutes or less, for example, about 140 minutes or less, about 130 minutes or less, about 120 minutes or less, about 110 minutes or less, or about 100 minutes or less. Since the constant temperature pyrolysis process is performed by maintaining the operating temperature environment constant for such a range of time, it may be more advantageous for the second coating layer (22) to have physical and chemical properties optimized for the technical effect of the composite particle (100).

[0137] Referring to FIG. 2, the second coating layer (22) manufactured according to one embodiment may have a structure that surrounds at least a portion of the outer surface of the core particle (10); a structure that surrounds at least a portion of the inner surface of the core particle (10); a structure that surrounds at least a portion of the surface of the first coating layer (21); or a structure corresponding to at least two or more of these structures. In one embodiment, the second coating layer (22) may necessarily include a structure that surrounds at least a portion of the surface of the first coating layer (21). The volume expansion buffering effect can be further enhanced by the composite particle (100) including a multi-stage coating structure of the first coating layer (21) and the second coating layer (22), more specifically, a double coating structure.

[0138] In the core particle (10) and the second coating layer (22) manufactured according to one embodiment, the content of the carbon component in the second coating layer (22) relative to 100 parts by weight of the crystalline silicon (c-Si) in the core particle (10) may be about 1 part by weight or more, for example, about 1.5 parts by weight or more, about 2 parts by weight or more, about 2.5 parts by weight or more, about 3 parts by weight or more, about 3.5 parts by weight or more, about 4 parts by weight or more, about 4.5 parts by weight or more, about 5 parts by weight or more, about 5.5 parts by weight or more, about 6 parts by weight or more, about 6.5 parts by weight or more, about 7 parts by weight or more, or about 7.5 parts by weight or more. In addition, the content of the carbon component in the second coating layer (22) relative to 100 parts by weight of the crystalline silicon (c-Si) in the core particle (10) may be about 20 parts by weight or less, for example, less than about 20 parts by weight, about 19 parts by weight or less, about 18 parts by weight or less, about 17 parts by weight or less, about 16 parts by weight or less, about 15 parts by weight or less, about 14 parts by weight or less, about 13 parts by weight or less, about 12 parts by weight or less, about 11 parts by weight or less, about 10 parts by weight or less, or less than about 10 parts by weight.

[0139] The second coating layer (22) manufactured according to one embodiment comprises the carbon component, and the carbon component may comprise one selected from the group consisting of amorphous carbon, low-crystalline carbon, pyrolytic carbon, and combinations thereof.

[0140] The composite particle manufactured according to the method (110) for manufacturing the composite particle according to one embodiment comprises the core particle (10), the first coating layer (21), and the second coating layer (22), wherein the first coating layer (21) is disposed on at least a portion of the inner surface and the outer surface of the core particle (10), and the second coating layer (22) may be disposed on at least a portion of the inner surface of the core particle (10), the outer surface of the core particle (10), and the surface of the first coating layer (21). Additionally, the core particle (10) may comprise crystalline silicon (c-Si), the first coating layer (21) may comprise amorphous silicon (a-Si), and the second coating layer (22) may comprise a carbon component. In this way, the composite particles manufactured according to one embodiment have a composite structure of crystalline silicon (c-Si) and amorphous silicon (a-Si) and introduce a carbon component as the outermost surface layer, thereby solving the problem caused by volume expansion of conventional silicon-based negative electrode active materials and, at the same time, achieving the effects of improved electrical conductivity and improved battery efficiency.

[0141] The composite particles manufactured according to one embodiment may have a value of [Equation 1] greater than about 1.5%, for example, about 1.6% or more, about 1.7% or more, or about 1.8% or more. Additionally, the value of [Equation 1] may be about 15.0% or less, for example, about 14.5% or less, about 14.0% or less, about 13.5% or less, about 13.0% or less, about 12.5% ​​or less, about 12.0% or less, about 11.5% or less, about 11.0% or less, or 10.5% or less. The above [Equation 1] is an indicator that quantitatively represents the ratio of the first coating layer (21) and the second coating layer (22) to the entire composite particle, and it may be more advantageous for the technical purpose of the entire composite particle to be excellently realized by introducing each component corresponding to satisfying the aforementioned range.

[0142] The composite particles manufactured according to one embodiment may have a particle size (D50) of about 15 μm or more at the point of 50 volume% of the cumulative distribution standard, for example, about 15.5 μm or more, about 16 μm or more, about 16.5 μm or more, or about 17 μm or more. Additionally, it may be about 25 μm or less, for example, about 24.5 μm or less, about 24 μm or less, about 23.5 μm or less, about 23 μm or less, about 22.5 μm or less, about 22 μm or less, about 21.5 μm or less, about 21 μm or less, about 20.5 μm or less, about 20 μm or less, about 19.5 μm or less, or about 19 μm or less. Since the D50 of the above composite particle satisfies this range, it may be advantageous for uniform coating without voids in the active material slurry during the process of utilizing it as an electrode active material, and the quantitative ratio of the first coating layer (21) and the second coating layer (22) satisfying [Equation 1] may be more advantageous in realizing the technical effect intended by the above composite particle (100).

[0143] Referring to FIG. 2, the step of preparing the first raw material composition (111), the step of preparing the second raw material composition (113), and the step of preparing the third raw material composition (115) may be performed regardless of their mutual chronological order. Each step of preparing the first, second, and third raw material compositions may be performed simultaneously, for example, or sequentially.

[0144] The method for manufacturing the above composite particles comprises an efficient process means capable of manufacturing the above composite particles (100) according to one embodiment, thereby allowing the above composite particles (100) manufactured through the method to have a physical and chemical structure capable of optimally expressing their technical effects. As a result, the above composite particles manufactured through the method can be applied as a negative electrode active material of a secondary battery to achieve an enhanced effect in terms of maintaining a stable structure and realizing excellent electrochemical performance.

[0145]

[0146] [Rechargeable Battery]

[0147] In another embodiment of the present invention, a secondary battery is provided comprising: a cathode including a cathode active material layer and a cathode current collector; an anode including an anode active material layer and an anode current collector; and an electrolyte disposed between the cathode and the anode, wherein the cathode active material layer comprises a cathode active material, and the cathode active material comprises a composite particle, and the composite particle comprises a core particle; a first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and a second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer; wherein the core particle comprises a crystalline silicon (c-Si) component, the first coating layer comprises an amorphous silicon (a-Si) component, and the second coating layer comprises a carbon component.

[0148] Recently, there has been a growing demand for negative electrodes containing silicon (Si)-based materials instead of graphite to increase cell energy density and manufacture thinner and lighter secondary batteries. However, compared to graphite, silicon (Si) has a higher tendency for volume expansion and repeated fracture during charging, raising concerns about potential issues such as cracking and particle pulverization. The secondary battery according to one embodiment solves the technical problems of conventional silicon (Si)-based active materials by applying the composite particles as the negative electrode active material. By applying the composite particles, which are characterized by a combination of the core particles, the first coating layer, and the second coating layer, to the negative electrode active material, volume expansion is effectively suppressed, problems such as the formation of an unstable solid electrolyte interface (SEI) layer and reduced conductivity are resolved, and technical advantages are realized in which excellent electrochemical performance is maintained for a long time even under repeated charge and discharge conditions.

[0149] FIG. 3 schematically illustrates the cross-sectional structure of the secondary battery (200) according to one embodiment.

[0150] Referring to FIG. 3, the secondary battery (200) may include the negative electrode (30) and the positive electrode (40) having a structure facing the negative electrode (30). Additionally, the negative electrode (30) may include the negative electrode active material layer (31) and the negative electrode current collector (32), and the positive electrode (40) may include the positive electrode active material layer (41) and the positive electrode current collector (42).

[0151] In one embodiment, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material may comprise the composite particle (100).

[0152] In the secondary battery (200) above, the composite particle may be the composite particle (100) according to the embodiment described above with reference to FIG. 1. Matters concerning the composite particle and its sub-composition applied to the secondary battery (200) may be applied substantially identically, either independently or in any combination, to the extent that there is no technical contradiction, even if all features of the composite particle (100) according to the embodiment are not repeatedly described in this specification.

[0153] In the secondary battery (200) above, the composite particles may be particles manufactured by the method (110) for manufacturing the composite particles according to the embodiment described above with reference to FIG. 2. Matters concerning the method for manufacturing the composite particles applied to the secondary battery (200) may be applied substantially identically, either independently or in any combination, to the extent that there is no technical contradiction, even if all features of the method (110) for manufacturing the composite particles according to the embodiment are not repeatedly described in this specification.

[0154] The above-mentioned cathode active material may further include an additional active material together with the above-mentioned composite particles. The additional active material may include, for example, one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, carbon microspheres, nitrogen-doped carbon (N-doped carbon), gold (Au), silver (Ag), copper (Cu), germanium (Ge), silicon (Si), aluminum (Al), tin (Sn), zinc (Zn), antimony (Sb), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), and combinations thereof.

[0155] The content of the composite particles in 100 weight% of the total negative electrode active material may be about 70 weight% or more, for example, about 75 weight% or more, about 80 weight% or more, about 85 weight% or more, about 90 weight% or more, or about 95 weight% or more. Additionally, the content of the composite particles in 100 weight% of the total negative electrode active material may be about 100 weight% or less.

[0156] In the secondary battery (200) according to one embodiment, the content of the crystalline silicon (c-Si) in the entire composite particle may be about 50 weight% or more, for example, greater than about 50 weight%, greater than about 55 weight%, greater than about 60 weight%, or greater than about 60 weight%. Additionally, the content of the crystalline silicon (c-Si) in the entire composite particle (100) may be about 90 weight% or less, for example, less than about 90 weight%, less than about 85 weight%, less than about 80 weight%, less than about 75 weight%, less than about 70 weight%, less than about 70 weight%, or less than about 69 weight%.

[0157] In one embodiment, the composite particles may have an amorphous silicon (a-Si) content of about 5 parts by weight or more relative to 100 parts by weight of crystalline silicon (c-Si), for example, about 5.5 parts by weight or more, about 6 parts by weight or more, about 6.5 parts by weight or more, or about 7 parts by weight or more. Additionally, the amorphous silicon (a-Si) content may be about 35 parts by weight or less relative to 100 parts by weight of crystalline silicon (c-Si), for example, 30 parts by weight or less, or about 25 parts by weight or less.

[0158] In one embodiment, the composite particle may contain about 1 part by weight or more of the carbon component relative to 100 parts by weight of the crystalline silicon (c-Si), and, for example, may contain about 1.5 parts by weight or more, about 2 parts by weight or more, about 2.5 parts by weight or more, about 3 parts by weight or more, about 3.5 parts by weight or more, about 4 parts by weight or more, about 4.5 parts by weight or more, about 5 parts by weight or more, about 5.5 parts by weight or more, about 6 parts by weight or more, about 6.5 parts by weight or more, about 7 parts by weight or more, or about 7.5 parts by weight or more. Additionally, the composite particle (100) may contain about 20 parts by weight or less of the carbon component relative to 100 parts by weight of the crystalline silicon (c-Si), for example, less than about 20 parts by weight, about 19 parts by weight or less, about 18 parts by weight or less, about 17 parts by weight or less, about 16 parts by weight or less, about 15 parts by weight or less, about 14 parts by weight or less, about 13 parts by weight or less, about 12 parts by weight or less, about 11 parts by weight or less, about 10 parts by weight or less, or less than about 10 parts by weight.

[0159] In the secondary battery (200) according to one embodiment, the value of [Equation 1] may be greater than about 1.5%, for example, about 1.6% or more, about 1.7% or more, or about 1.8% or more. Additionally, the value of [Equation 1] may be about 15.0% or less, for example, about 14.5% or less, about 14.0% or less, about 13.5% or less, about 13.0% or less, about 12.5% ​​or less, about 12.0% or less, about 11.5% or less, about 11.0% or less, or 10.5% or less.

[0160] In one embodiment, the negative electrode active material layer (31) may further include a binder.

[0161] In one embodiment, the binder is styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorinated resin, sodium / lithium alginate, guar gum, xanthan gum, pullulan, pectin, carrageenan, chitosan, carboxymethyl chitosan, cellulose nanofiber, polyurethane, styrene-acrylate copolymer, catechol-functional polymer, It may include one selected from the group consisting of boronate-crosslinked polyvinyl alcohol (Boronate-crosslinked PVA), ureidopyrimidinone-functional polymer, imine-based dynamic covalent polymer, polyurethane / urea-based polymer, ionomeric binder, and combinations thereof.

[0162] In one embodiment, the negative electrode active material layer (31) may contain about 0 parts by weight or more of the binder with respect to 100 parts by weight of the negative electrode active material, for example, about 0.5 parts by weight or more, about 1 part by weight or more, about 1.5 parts by weight or more, about 2 parts by weight or more, about 2.5 parts by weight or more, about 3 parts by weight or more, or about 3.5 parts by weight or more. Additionally, the binder may contain about 20 parts by weight or less, for example, about 15 parts by weight or less, or about 10 parts by weight or less. The binder is a component for ensuring adhesion and interfacial stability between the negative electrode active material layer and the negative electrode current collector, but if an excessive amount is used or if a specific functional group is contained in excess, there is a risk of causing problems such as lowering electrical conductivity, causing the solid electrolyte interface layer (SEI) to enlarge, or lowering the initial Coulomb efficiency (ICE). Accordingly, by including the binder in the aforementioned amount in the cathode active material layer (31), it may be more advantageous in terms of ensuring adhesion and interfacial stability between the cathode active material layer (31) containing the composite particles and the cathode current collector (32), while simultaneously reliably exhibiting the battery performance enhancement effect by the composite particles.

[0163] In one embodiment, the negative electrode active material layer (31) may further include a conductive component. In one embodiment, the conductive component is intended to improve electrical conductivity and may include, for example, one selected from the group consisting of high-structure carbon black, carbon nanotube (CNT), carbon nanofiber (CNF), graphene, acetylene black, furnace black, thermal black, Supreme P, Ketjen black, and combinations thereof.

[0164] In one embodiment, the negative electrode active material layer (31) may contain about 0 parts by weight or more of the conductive component with respect to 100 parts by weight of the negative electrode active material, for example, about 0.1 parts by weight or more, and may also contain about 15 parts by weight or less, for example, about 10 parts by weight or less, about 9.5 parts by weight or less, about 9.0 parts by weight or less, about 8.5 parts by weight or less, about 8.0 parts by weight or less, about 7.5 parts by weight or less, about 7.0 parts by weight or less, about 6.5 parts by weight or less, about 6.0 parts by weight or less, about 5.5 parts by weight or less, about 5.0 parts by weight or less, about 4.5 parts by weight or less, about 4.0 parts by weight or less, about 3.5 parts by weight or less.

[0165] In one embodiment, the negative current collector (32) may be a conductive metal thin film.

[0166] In one embodiment, the negative current collector (32) may include one selected from the group consisting of copper (Cu), nickel (Ni), iron (Fe), chromium (Cr), cobalt (Co), zinc (Zn), tungsten (W), molybdenum (Mo), gold (Au), silver (Ag), tin (Sn), palladium (Pd), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), lead (Pb), aluminum (Al), and combinations thereof.

[0167] In one embodiment, the thickness of the negative current collector (32) may be about 3 μm or more, for example, about 4 μm or more, about 5 μm or more, about 6 μm or more, about 7 μm or more, about 8 μm or more, about 9 μm or more, or about 10 μm or more. Additionally, the thickness of the negative current collector (32) may be about 15 μm or less, for example, about 14 μm or less, about 13 μm or less, or about 12 μm or less.

[0168] In one embodiment, the positive active material layer (41) comprises a positive active material, and the positive active material may comprise a lithium (Li) transition metal oxide. The positive active material is, for example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi 1-x-y Co x Mn y O2), lithium nickel cobalt aluminum oxide (LiNi 1-x-y Co x Al y O2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), lithium manganese aluminum oxide (LiMn 2-x Al x O4), lithium nickel manganese aluminum oxide (LiNi x Mn y Al z It may include one selected from the group consisting of O) and combinations thereof.

[0169] In one embodiment, the particle size (D50) at the point of 50 volume% of the cumulative distribution of the positive active material may be, for example, about 0.1 μm or more, for example, about 0.5 μm or more, about 1 μm or more, or about 1.5 μm or more. Additionally, the D50 of the positive active material may be about 20 μm or less, for example, about 10 μm or less.

[0170] In one embodiment, the positive active material layer (41) may further include a binder. The binder may include, for example, one selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethylcellulose (CMC), polyacrylic acid (PAA), and combinations thereof.

[0171] In one embodiment, the positive active material layer (41) may contain about 1 part by weight or more of the binder relative to 100 parts by weight of the positive active material, for example, about 2 parts by weight or more, about 3 parts by weight or more, about 4 parts by weight or more, or about 5 parts by weight or more, and may also contain about 15 parts by weight or less.

[0172] In one embodiment, the positive active material layer (41) may further include a conductive component. The conductive component may include, for example, one selected from the group consisting of acetylene black, carbon black, graphite, carbon nanotubes (CNT), and combinations thereof.

[0173] In one embodiment, the positive active material layer (41) may contain at least about 0.1 parts by weight of the conductive component relative to 100 parts by weight of the positive active material, for example, at least about 0.5 parts by weight, at least about 0.8 parts by weight, at least about 1 part by weight, at least about 2 parts by weight, or at least about 3 parts by weight, and may also contain at least about 15 parts by weight, for example, at least about 10 parts by weight, at least about 8 parts by weight, or at least about 6 parts by weight.

[0174] In one embodiment, the positive current collector (42) may be a form selected from the group consisting of a thin film, a foil, a sheet, a net, a porous material, a foam material, and combinations thereof.

[0175] In one embodiment, the positive current collector (42) may include one selected from the group consisting of iron (Fe), chromium (Cr), titanium (Ti), aluminum (Al), silver (Ag), nickel (Ni), manganese (Mn), carbon (C), and combinations thereof. Specifically, the positive current collector (42) may include one selected from the group consisting of aluminum (Al), aluminum alloy, iron-chromium-nickel alloy, and combinations thereof.

[0176] In one embodiment, the thickness of the positive current collector (42) may be about 3 µm to about 500 µm, for example, about 3 µm to about 300 µm, for example, about 3 µm to about 200 µm, for example, about 3 µm to about 100 µm, for example, about 3 µm to about 80 µm, for example, about 3 µm to about 60 µm, for example, about 3 µm to about 50 µm, for example, about 3 µm to about 30 µm.

[0177] Referring to FIG. 3, the secondary battery (200) may include an electrolyte (50) disposed between the negative electrode (30) and the positive electrode (40). The electrolyte is a selective conductor that blocks electrons and moves ions, and needs to be designed with an appropriate composition and structure to chemically and / or electrochemically interact with the negative electrode active material layer (31) or the positive electrode active material layer (41) to suppress side reactions, reduce metal leaching, and prevent changes in the electrode structure.

[0178] In one embodiment, the electrolyte (50) may include one selected from the group consisting of a non-aqueous electrolyte, a solid electrolyte, a gel electrolyte, and combinations thereof.

[0179] In one embodiment, the electrolyte (50) comprises a non-aqueous electrolyte, and the non-aqueous electrolyte may comprise an electrolyte salt and a non-aqueous organic solvent. Specifically, the non-aqueous electrolyte may comprise an electrolyte salt, a non-aqueous organic solvent and at least one additive.

[0180] The above electrolyte salt may include, for example, one selected from the group consisting of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perfluoroethylsulfonate (LiCF3SO3), lithium tetrafluoroborate (LiBF4), lithium chloroaluminate (LiAlCl4), and combinations thereof.

[0181] The above-mentioned non-aqueous organic solvent may include, for example, one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), dipropyl carbonate (DPC), vinylene carbonate (VC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, propylene sulfide, tetrahydrofuran, and combinations thereof.

[0182] The above additive may include, for example, one selected from the group consisting of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), lithium difluoro(oxalato)borate (LiDFOB), p-toluene sulfonic acid, trimethyl phosphate (TMP), and combinations thereof.

[0183] In one embodiment, the electrolyte (50) comprises a solid electrolyte, and the solid electrolyte is a solid medium having ion conductivity, such as Li7La3Zr2O 12 (LLZO), Li 1.3 Al 0.3 Ti 1.7 Oxide-based electrolytes such as (PO4)3(LATP); Li 10 GeP2S 12 It may include one selected from the group consisting of sulfide-based electrolytes such as (LGPS) and Li2S-P2S5; polymer-based electrolytes such as polyethylene oxide (PEO) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP); and combinations thereof.

[0184] Referring to FIG. 3, the secondary battery (200) according to one embodiment may further include a separator (60) disposed between the negative electrode (30) and the positive electrode (40).

[0185] In one embodiment, the secondary battery (200) may further include a separator (60) disposed between the negative electrode (30) and the positive electrode (40), wherein the electrolyte (50) comprises a non-aqueous electrolyte.

[0186] In another embodiment, the secondary battery (200) may not include a separator (60) disposed between the negative electrode (30) and the positive electrode (40), wherein the electrolyte (50) comprises a solid electrolyte.

[0187] The above separator (60) may include, for example, one selected from the group consisting of polyethylene (PE), polypropylene (PP), ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, polyamide (PA), polyimide (PI), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET) and combinations thereof.

[0188] In one embodiment, the total thickness of the separator (60) may be about 5 μm or more, for example, about 6 μm or more, for example, about 7 μm or more, for example, about 8 μm or more, for example, about 9 μm or more, for example, about 10 μm or more, for example, about 30 μm or less, for example, about 25 μm or less.

[0189] In one embodiment, the porosity of the separator (60) may be about 30 volume% or more, for example, about 35 volume% or more, for example, about 65 volume% or less, for example, about 60 volume% or less.

[0190] By applying the composite particles according to one embodiment as the negative electrode active material, the above secondary battery can effectively suppress the formation and hypertrophy of the unstable solid electrolyte interface layer (SEI) observed in conventional silicon-based active materials, solve the problem of reduced electrical conductivity, and realize the technical advantage of maintaining excellent electrochemical performance for a long time even under repeated charge and discharge conditions.

[0191]

[0192] Specific embodiments of the present invention are presented below. However, the embodiments described below are merely for the purpose of specifically illustrating or explaining the present invention, and the scope of the present invention is not to be interpreted as limited by this, and the scope of the present invention is determined by the claims.

[0193]

[0194] <Examples and Comparative Examples>

[0195] Example 1

[0196] Silicon nanoparticles (nano-Si) with an average particle size of about 70 nm were dispersed in an anhydrous ethanol solvent, and a colloidal silica solution with a solid content of 10 wt% was prepared. Graphite was dispersed and mixed in the colloidal silica solution to prepare a first raw material composition.

[0197] The above first raw material composition was processed using a spray dryer (FineTech, FSD-1.5R) under conditions of a raw material inflow rate of 300 mL / min, an atomizer of 20,000 rpm, a drying temperature of 100℃, and an exhaust temperature of 65℃ to produce core particles containing a mixture of crystalline silicon (c-Si) and graphite.

[0198] Next, a second raw material composition containing 100 volume% of silane (SiH4) was prepared, and the core particles and the second raw material composition were supplied to a thermal chemical vapor deposition (Thermal CVD, Scientech) equipment and processed for 30 minutes under conditions of a deposition temperature of 450°C and a pressure of 101.3 kPa to form a first coating layer containing amorphous silicon (a-Si) on the surface of the core particles.

[0199] Next, a third raw material composition comprising 10 volume% acetylene (C2H2) and 90 volume% nitrogen (N2) was prepared. The third raw material composition was supplied to the core particle on which the first coating layer was formed, and a carbon coating was performed using a constant temperature pyrolysis method at 500°C for 60 minutes, thereby forming a second coating layer, which is a surface carbon layer. Afterward, it was naturally cooled in an inert atmosphere.

[0200] Thus, a composite particle comprising the above-mentioned core particle, the first coating layer, and the second coating layer was manufactured.

[0201]

[0202] Example 2

[0203] In Example 1 above, the second raw material composition was supplied to a Thermal CVD (Scientech) equipment and processed for a time of more than 30 minutes and less than 90 minutes under conditions of a deposition temperature of 450°C and a pressure of 760 Torr, and composite particles were manufactured in the same manner except that the content of the first coating layer containing amorphous silicon (a-Si) was varied as shown in [Table 1] below.

[0204]

[0205] Example 3

[0206] In Example 1 above, the second raw material composition was supplied to a Thermal CVD (Scientech) equipment and processed for 90 minutes under conditions of a deposition temperature of 450°C and a pressure of 760 Torr, and composite particles were prepared in the same manner except that the content of the first coating layer containing amorphous silicon (a-Si) was varied as shown in [Table 1] below.

[0207]

[0208] Comparative Example 1

[0209] In the above Example 1, a composite particle was manufactured in the same way, except that the process of forming the first coating layer on the core particle was omitted and the second coating layer was formed.

[0210]

[0211] The composition and content of each composite particle of the above examples and comparative examples are listed in [Table 1] below. In addition, the composition of each composite particle of the above examples and comparative examples is listed in [Table 2] below, converted into a relative content ratio (unit: parts by weight) with respect to 100 parts by weight of crystalline silicon (c-Si).

[0212] Classification Core Particle 1st Coating Layer 2nd Coating Layer c-Si Graphite a-Si Carbon Unit wt% wt% wt% wt% Example 167 2355 Example 264 21105 Example 361 19155 Comparative Example 170 25-5

[0213] Classification Core Particle 1st Coating Layer 2nd Coating Layer c-Si Graphite a-Si Carbon Unit Weight Part Weight Part Weight Part Weight Example 1 10034.37.57.5 Example 2 10032.815.67.8 Example 3 10031.124.68.2 Comparative Example 110035.7-7.1

[0214]

[0215] Measurement and Evaluation

[0216] Measurement Example 1: Size of Composite Particles

[0217] For each of the core particles and composite particles of the above examples and comparative examples, a water-dispersed sample was prepared at a concentration of about 0.5 (±0.2) mg / L, and the D50 of the particles was measured using a laser diffraction and scattering particle size analyzer (PSA) instrument (Mastersizer 3000, Malvern Panalytical).

[0218] In addition, the values ​​of D50(Lc) of the core particle and D50(Lt) of the composite particle were substituted into the following [Equation 1] to derive the values.

[0219] The results are as shown in [Table 3] below.

[0220]

[0221] Classification D50 Formula 1 Core Particle Composite Particle Unit µm µm% Example 1 16.7 2 17.0 2 1.8 Example 2 16.8 1 17.4 6 3.7 Example 3 16.7 6 18.6 6 10.2 Comparative Example 1 16.8 5 17.1 11.5

[0222]

[0223] Evaluation Example 1: Energy Dispersive Spectral (EDS) Component Distribution Analysis

[0224] For the composite particles of Example 2 above, specimens were prepared by dispersing them onto a scanning electron microscope (SEM) stub attached with carbon tape, and analysis was performed using a focused ion beam scanning electron microscope (FIB-SEM; Helios NanoLab 600i, FEI) and an energy dispersive X-ray spectrometer (EDS; XFlash 6|130, BRUKER). EDS analysis was performed under conditions of a working distance of 4 mm and an analysis area of ​​approximately 15 μm × 11 μm (= 160 μm²).

[0225] The results are as shown in [Fig. 4]. Specifically, (a) of Fig. 4 is the result for the core particle, (b) is the result for a particle with the first coating layer formed on the core particle, and (c) is the result for a particle with the core particle, the first coating layer, and the second coating layer formed on it.

[0226]

[0227] Evaluation Example 2: Raman Spectroscopic Analysis

[0228] For each of the composite particles of the above examples and comparative examples, a specimen was prepared by uniformly dispersing the powdered sample onto a sample holder or glass slide, and a Micro Raman Spectroscopy (Olympus, BX51) was used with an excitation wavelength of 532 nm and a resolution (grating) of 1 to 2 cm⁻¹ -1 Raman spectroscopic spectra were obtained under conditions of accumulation (acquisition) time: 2 to 10 seconds / scan. The resulting graph is shown in [Fig. 5].

[0229]

[0230] Evaluation Example 3: Battery Capacity Retention Rate

[0231] An active material was prepared by mixing 16.3 parts by weight of composite particles and 83.7 parts by weight of graphite, each of the above examples and comparative examples. Then, 2 parts by weight of carboxymethylcellulose (CMC) and 2 parts by weight of styrene-butadiene rubber (SBR) were mixed as binders relative to 100 parts by weight of the active material, and distilled water was applied as a solvent to prepare a slurry having a solid content of approximately 45 (±5) weight%.

[0232] The above slurry is applied to the top of copper foil using a doctor blade with an area-to-area capacity of approximately 3.5 (±0.5) mAh / cm² 2 The coating was applied to achieve this. Subsequently, the negative electrode plate was manufactured by first drying at approximately 80(±5) ℃, and after a rolling process, second drying for 3 hours under a vacuum atmosphere at approximately 120(±5) ℃.

[0233] A solution containing 1.0 M lithium hexafluorophosphate (LiPF6) salt as the electrolyte and with a volume ratio of ethylene carbonate (EC) / ethylmethyl carbonate (EMC) / diethyl carbonate (DEC) of 3 / 4 / 4, to which 10% by weight of fluoroethylene carbonate (FEC) was added, was used.

[0234] A battery cell was manufactured using lithium (Li) metal as the positive electrode and a polypropylene (PP) film as the separator.

[0235] For each battery cell, the discharge current rate (C-rate) was measured in the order of 0.2C, 0.5C, 1C, 2C, and 0.2C, and the battery capacity was evaluated according to the following measurement protocol.

[0236] 1. Formation cycle: 0.1C, 2 times

[0237] 2. Standard: 0.2C, per use

[0238] 3. Life Cycle: 50 times at 0.5C

[0239] In addition, the capacity retention rate was calculated as a percentage (%) of the 0.5C, 50-cycle remaining capacity relative to the 0.5C, 1-cycle discharge capacity.

[0240] The results are shown in [Table 4] and [Figure 6] below.

[0241]

[0242] Classification Si Converted Standard Capacity Initial Coulomb Efficiency Capacity Retention Rate Unit mAh / g ICE% Example 1 2,313 88.05 9.6 Example 2 2,440 90.28 5.8 Example 3 2,368 87.57 5.2 Comparative Example 1 2,185 87.13 3.3

[0243]

[0244] 100: Composite particles

[0245] 10: Core Particle

[0246] 20: Coating layer

[0247] 21: First coating layer

[0248] 22: Second coating layer

[0249] 110: Method for manufacturing composite particles

[0250] 111: Step of preparing the first raw material composition

[0251] 112: Step of manufacturing core particles

[0252] 113: Step of preparing the second raw material composition

[0253] 114: Step of manufacturing the first coating layer

[0254] 115: Step of preparing the third raw material composition

[0255] 116: Step of manufacturing the second coating layer

[0256] The present invention relates to a composite particle comprising two or more components, a method for manufacturing the composite particle, and a secondary battery in which the composite particle is applied as an electrode active material.

Claims

1. Core particle; A first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and A second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer; comprising The above core particles contain crystalline silicon (c-Si) components, and The first coating layer comprises an amorphous silicon (a-Ci) component, and The above second coating layer contains a carbon component, Composite particles.

2. In Paragraph 1, Based on 100 parts by weight of the above crystalline silicon (c-Si), The above amorphous silicon (a-Si) content is 5 parts by weight or more and 35 parts by weight or less, Composite particles.

3. In Paragraph 1, The above core particles further include graphite, Composite particles.

4. In either Paragraph 1 or Paragraph 3, Based on 100 parts by weight of the above crystalline silicon (c-Si), The graphite content is 5 parts by weight or more and 35 parts by weight or less, Composite particles.

5. In Paragraph 1, The following [Formula 1] is greater than 1.5% and less than or equal to 15.0%, Composite particles: [Formula 1] In the above [Formula 1], The above Lc is the particle size (D50) at the 50 volume% point of the cumulative distribution of the core particles, and The above Lt is the particle size (D50) at the 50 volume% point of the cumulative distribution of the above composite particles.

6. In Paragraph 5, The particle size (D50) at the 50 volume% point of the cumulative distribution of the above composite particles is 15㎛ or more and 25㎛ or less, Composite particles.

7. A step of preparing a first raw material composition comprising a crystalline silicon (c-Si) providing component; A step of manufacturing core particles containing crystalline silicon (c-Si) by processing the above-mentioned first raw material composition using a spray drying method; A step of preparing a second raw material composition comprising an amorphous silicon (a-Si) providing component; A step of manufacturing a first coating layer comprising amorphous silicon (a-Si) by processing the second raw material composition using a chemical vapor deposition (CVD) method to surround at least a portion of the inner surface of the core particle and the outer surface of the core particle; A step of preparing a third raw material composition containing a carbon-providing component; and A step of preparing a second coating layer containing a carbon component, which surrounds at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer from the third raw material composition; Method for manufacturing composite particles.

8. In Paragraph 7, The above crystalline silicon (c-Si) providing component includes silicon particles, and The average particle size of the above silicon particles is 40 nm or more and less than 100 nm, Method for manufacturing composite particles.

9. In Paragraph 8, The above first raw material composition is, It includes a dispersion of the above silica particles, A dispersion of the above silica particles having a solid content of 3% or more and 15% or less by weight, Method for manufacturing composite particles.

10. In Paragraph 7, The above first raw material composition further comprises graphite, Method for manufacturing composite particles.

11. In Paragraph 7, The above spray drying method is, Performed under conditions of an inflow flow rate of the first raw material composition of 100 mL / min or more and 500 mL / min or less, Method for manufacturing composite particles.

12. In Paragraph 7, The above amorphous silicon (a-Si) providing component comprises one selected from the group consisting of hydrogenated silanes, silazanes, aminosilanes, silicon halides, organosilicon compounds, and combinations thereof. Method for manufacturing composite particles.

13. In Paragraph 7, The content of the amorphous silicon (a-Si) providing component in the second raw material composition is 99 volume% or more and 100 volume% or less, Method for manufacturing composite particles.

14. In Paragraph 7, The above carbon-providing components are acetylene (C2H2), ethylene (C2H4), ethane (C2H6), propene (C3H6), butadiene (C4H6), methane (CH4), ethane (C2H6), propane (C3H8), and butane (C4H 10 ), comprising one selected from the group consisting of benzene (C6H6), toluene, tar, phenol, phenolic resin, polyacrylonitrile (PAN), pitch, and combinations thereof, Method for manufacturing composite particles.

15. In Paragraph 7, The above third raw material composition comprises the carbon-providing component in an amount of 5 volume% or more and 15 volume% or less, Method for manufacturing composite particles.

16. A cathode comprising a cathode active material layer and a cathode current collector; Anode comprising an anode active material layer and an anode current collector; and Includes an electrolyte disposed between the above-mentioned cathode and the above-mentioned anode; The above-mentioned negative electrode active material layer includes a negative electrode active material, The above-mentioned cathode active material includes composite particles, and The above composite particles, Core particle; A first coating layer surrounding at least a portion of the inner surface of the core particle and the outer surface of the core particle; and A second coating layer surrounding at least a portion of the inner surface of the core particle, the outer surface of the core particle, and the surface of the first coating layer; comprising, The above core particles contain crystalline silicon (c-Si) components, and The first coating layer comprises an amorphous silicon (a-Si) component, and The above second coating layer contains a carbon component, Secondary battery.

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