Active material structure for lithium ion battery and method for manufacturing same

Abstract

An active material structure for a lithium ion battery, according to one embodiment of the present invention, comprises: silicon active particles having a median particle size of 2 μm to 5 μm; a carbon coating layer surrounding the surface of the silicon active particles; and conductive metal particles located in a partial region within the carbon coating layer and having a grain size of 60 nm to 80 nm, wherein the content of the conductive metal particles is 5 wt% to 18 wt%.

Description

Active material structure for lithium-ion batteries and method for manufacturing the same

[0001] The present invention relates to an active material structure for a lithium-ion battery and a method for manufacturing the same, and more specifically, to a silicon-based active material structure for a lithium-ion battery that provides high energy density while improving electrode stability and lifespan, and a method for manufacturing the same.

[0002] Lithium-ion batteries are used as essential energy storage devices in various industries, including electronic devices, electric vehicles, and energy storage systems (ESS), and cathode material technology is continuously advancing to provide higher energy density and longer lifespan. Conventionally, graphite has been primarily used as a cathode material due to its stability and long lifespan; however, graphite has limitations as a cathode material because its theoretical electric capacity (372 mAh / g) is relatively low.

[0003] Silicon (Si), which is attracting attention as a next-generation cathode material, possesses a high theoretical electric capacity (3600 mAh / g) approximately 10 times that of graphite, giving it great potential in applications requiring high energy density. However, silicon experiences volume expansion during the charging and discharging process, which can act as a major cause of structural collapse and reduced lifespan of the electrode. Additionally, silicon itself has low conductivity, which restricts electron movement within the electrode and can lead to a degradation of electrochemical performance.

[0004] To address these limitations, technologies such as adding conductive materials to cathode materials or stabilizing the silicon surface are being researched. However, the use of conductive materials can increase the proportion of inert materials within the electrode, which can lower energy density, and it remains difficult to fundamentally resolve the volume expansion problem. Accordingly, a technical approach is required to maximize the performance and stability of silicon cathodes without the use of conductive materials.

[0005] One aspect of the present invention, aimed at solving the aforementioned problems, is to provide an active material structure for a lithium-ion battery that improves structural stability by effectively controlling the volume expansion of a silicon active material, while also enhancing electrical conductivity without the addition of a conductive material. Furthermore, the invention is to provide a method for manufacturing an active material structure for a lithium-ion battery that improves process efficiency and reduces costs.

[0006] The technical problems intended to be solved in this document are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this invention belongs from the description below.

[0007] An active material structure for a lithium-ion battery according to one embodiment of the present invention comprises silicon active particles having a central particle size of 2 to 5 μm, a carbon coating layer surrounding the surface of the silicon active particles, and conductive metal particles located in a part of the carbon coating layer having a crystal grain size of 60 to 80 nm, wherein the content of the conductive metal particles is 5 to 18% by weight.

[0008] The above conductive metal particles contain tin (Sn).

[0009] The carbon coating layer is 1 to 3% by weight.

[0010] The thickness of the carbon coating layer is 10 to 20 nm.

[0011] A method for manufacturing an active material structure for a lithium-ion battery according to one embodiment of the present invention comprises the steps of mixing a silicon active material including silicon active particles, a carbon precursor material, and a metal precursor material, and heating the mixture to 380 to 420°C in a nitrogen atmosphere, wherein as the mixture is heated, conductive metal particles are precipitated from the metal precursor material, and the crystal grain size of the precipitated conductive metal particles is 60 to 80 nm.

[0012] In the mixing step above, the metal precursor material is included in a ratio of 9 to 15 parts by weight per 100 parts by weight of the silicon active material.

[0013] The above conductive metal particles contain tin (Sn).

[0014] The above metal precursor material includes tin chloride (SnCl2).

[0015] The carbon precursor is included in a ratio of 10 to 12 parts by weight per 100 parts by weight of the silicon active material.

[0016] The carbon precursor comprises oleic acid and oleamine, and each of the oleic acid and oleamine is included in a ratio of 5 to 6 parts by weight per 100 parts by weight of the silicon active material.

[0017] The heating step includes maintaining the mixture at 380 to 420°C for 2 to 3 hours.

[0018] In the heating step above, the heating rate is 3 to 7℃ / min.

[0019] A method for manufacturing an active material structure for a lithium-ion battery further includes a step of performing purging in a nitrogen atmosphere for at least 2 hours prior to the heating step.

[0020] The central particle size of the silicon active particles included in the above silicon active material is 2 to 5 μm.

[0021] In the heating step, the silicon active material forms silicon active particles, the carbon precursor forms a carbon coating layer that coats each of the silicon active particles, and the thickness of the carbon coating layer is 10 to 20 nm.

[0022] According to one aspect of the present invention, an active material structure for a lithium-ion battery can be provided that improves structural stability by effectively controlling the volume expansion of a silicon active material, while also improving electrical conductivity without the addition of a conductive material. Furthermore, in manufacturing the active material structure for a lithium-ion battery, process efficiency can be improved and costs can be reduced.

[0023] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0024] FIG. 1 is a graph showing the change curves of the electrical capacity retention rate according to the number of charge / discharge cycles of embodiments according to the present invention.

[0025] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0026] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof.

[0027] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense. For instance, singular expressions in this specification include plural expressions unless the context clearly indicates an exception.

[0028] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0029] The active material structure for a lithium-ion battery and the method for manufacturing the same according to one embodiment of the present invention will be described in detail below.

[0030] The active material structure for a lithium-ion battery according to an embodiment of the present invention may be an active material used as a negative electrode material for a lithium-ion battery. Specifically, a negative electrode of a lithium-ion battery may be manufactured by arranging the active material structures according to an embodiment of the present invention on a current collector. In this case, a curable binder may be used to maintain physical bonding between the active material structures, physical bonding between the current collector and the active material structures, electrode durability, and electrochemical contact.

[0031] In this embodiment, the active material structure for a lithium-ion battery comprises silicon active particles, a carbon coating layer, and conductive metal particles.

[0032] Silicon active particles contribute to the charging and discharging of the battery through alloying and dealloying reactions with lithium ions. Silicon active particles have a spherical or semi-spherical shape, which allows the silicon active material to be uniformly mixed with carbon structures and metal precursors during the active material structure manufacturing process, and enables the silicon active particles to be uniformly coated with carbon.

[0033] In this embodiment, the silicon active particles may have a central particle size of 2 to 5 μm. The central particle size is defined as the average size of the silicon active particles. If the central particle size is less than 2 μm, the surface area increases excessively, leading to increased formation of the Solid Electrolyte Interface (SEI) and potentially increased initial capacity loss; if the central particle size exceeds 5 μm, it takes a long time for lithium ions to diffuse into the particle, which may result in inefficient charge-discharge reactions. In the present invention, by setting the central particle size range of the silicon active particles to 2 to 5 μm, the lithium diffusion distance and reaction uniformity are optimized, and structural stability is maintained. In this embodiment, the central particle size of the silicon active particles can be measured using a particle size analyzer (PSA) device.

[0034] The carbon coating layer is positioned to uniformly surround the surface of the silicon active particles. By preventing direct contact between the silicon active particles and the electrolyte, the carbon coating layer suppresses SEI formation and minimizes initial capacity loss. Additionally, the carbon coating layer physically limits the volume expansion of the silicon active particles and alleviates stress generated during the charge-discharge process, thereby improving the structural stability of the lithium-ion battery.

[0035] In an embodiment of the present invention, the content of the carbon coating layer may be 1 to 3% by weight. Additionally, the thickness of the carbon coating layer may be 10 to 20 nm.

[0036] The above range may be the optimal range for minimizing SEI formation while allowing smooth diffusion of lithium ions. Specifically, if the carbon coating layer is less than 1% or too thin with a thickness of 10 nm or less, it may not sufficiently cover the surface of the silicon active particles, leading to direct contact with the electrolyte. This can result in an excessive increase in SEI formation, leading to significant initial capacity loss and reduced charge-discharge safety. Additionally, a thin coating layer may fail to effectively suppress the volume expansion of the silicon active particles, potentially causing particle disintegration. On the other hand, if the carbon coating layer exceeds 3% and becomes thicker than 20 nm, the diffusion path of lithium ions lengthens, which may increase reaction resistance. Consequently, charge-discharge efficiency decreases, and the performance of the lithium-ion battery may deteriorate. Furthermore, since carbon does not store lithium ions, an excessive carbon coating can act as an inactive weight; this sacrifices the energy density of the silicon particles themselves, which may lead to a decrease in the overall capacity of the anode material.

[0037] A carbon coating layer can be formed by conversion from a carbon precursor. In the present embodiment, the carbon precursor may be oleic acid and oleilamine. However, the present invention is not limited thereto, and the carbon precursor material may be at least one of linoleic acid, linoleylamine, polyvinylpyrrolidone, citric acid, glycerol, dextran, coal tar, and pitch.

[0038] Conductive metal particles improve the electrical conductivity of the active material structure, thereby reducing internal resistance during the charging and discharging process of the lithium-ion battery and enabling the battery to maintain stable performance even at high current densities. In this embodiment, the conductive metal particles may be distributed in a portion of the carbon coating layer of the silicon active particle. For example, the conductive metal particles may be placed on top of the carbon coating layer or in a discontinuous portion of the carbon coating layer on the surface of the silicon active particle. That is, the conductive metal particles may overlap with the carbon coating layer, but may also be placed independently on the surface of the silicon active particle.

[0039] In this embodiment, the conductive metal particles may include tin (Sn). Tin can provide additional lithium storage capacity separate from the silicon active particles through an alloying reaction with lithium. Therefore, when the conductive metal particles include tin (Sn), the low conductivity of silicon can be compensated for even if the cathode does not contain a conductive material, because tin has excellent conductivity. Tin can effectively absorb or disperse the volume expansion stress of silicon.

[0040] In an embodiment of the present invention, the grain size of the conductive metal particles may be 60 to 80 nm. The grain size refers to the size formed by the conductive metal particles through a heat treatment process. The above range may be an optimized value to balance electrochemical performance and mechanical stability. For example, if the grain size becomes smaller than 60 nm, aggregation between particles may occur, which may reduce conductivity, and if it exceeds 80 nm, the lithium ion diffusion path may become longer, which may reduce reaction efficiency.

[0041] According to an embodiment of the present invention, the content of conductive metal particles can determine the size and distribution of conductive metal particles formed during heat treatment. If the content of conductive metal particles is low, the grain size may become too small or the formation may be incomplete; if the content is excessively high, the grain size may become excessively large or an excessive number of metal particles may be formed, which may reduce the uniformity of the cathode material.

[0042] Specifically, in this embodiment, the content of conductive metal particles may be 5 to 18% by weight. If the content of conductive metal particles is insufficient, metal particles may not be sufficiently formed during heat treatment, the grain size may become too small, or electrochemical performance may be degraded. In addition, the volume expansion buffering effect may also decrease, which may reduce the stability of the silicon active particles. On the other hand, if the content of conductive metal particles is excessively high, the size of the conductive metal particles may become excessively large, obstructing the lithium ion diffusion pathway, and the conductive metal particles may be excessively formed on the silicon surface, failing to effectively suppress the volume expansion of the silicon active particles. Furthermore, the electrochemical performance may be degraded due to the uneven distribution of conductive metal particles throughout the cathode material. In a more preferred embodiment of the present invention, the content of conductive metal particles may be 5 to 9%.

[0043] Hereinafter, a method for manufacturing an active material structure for a lithium-ion battery according to an embodiment of the present invention will be described.

[0044] A method for manufacturing an active material structure for a lithium-ion battery according to an embodiment of the present invention comprises the steps of: mixing a solution comprising a silicon active material including silicon active particles, a carbon precursor material, and a metal precursor material to prepare a mixture; performing purging in a nitrogen atmosphere for at least 2 hours; and heating the mixed mixture in a nitrogen atmosphere.

[0045] In this embodiment, the mixture may contain, in weight percent, 75-85% silicon active material, 8-9.5% carbon precursor material, 7-12% metal precursor material, and other impurities.

[0046] The content of the silicon active material may be 75 to 85%. If the content of the silicon active material is less than 75%, the distance between silicon particles in the mixture becomes too far, which may result in insufficient connectivity of the active material structure formed in subsequent processes. This may lead to a decrease in electrical conductivity and make it difficult to form a uniform structure. On the other hand, if the content of the silicon active material exceeds 85%, carbon precursors and metal precursors may not be sufficiently interposed between the silicon particles, which may cause excessive aggregation between particles during subsequent heat treatment. This may reduce the porosity of the final active material structure and hinder the formation of a uniform coating layer, making it difficult to obtain the structural characteristics intended by the present invention.

[0047] In the step of preparing the above mixture, the carbon precursor material is used to form a carbon coating layer surrounding the surface of the silicon active particle. In this embodiment, the content of the carbon precursor material may be 8 to 9.5%. That is, the carbon precursor material may be included in a ratio of 10 to 12 parts by weight per 100 parts by weight of the silicon active material. If the content of the carbon precursor material is less than 8% (10 parts by weight), the carbon coating layer is not sufficiently formed, which weakens the protective function of the silicon active particle surface and may result in the formation of excessive SEI. If the content of the carbon precursor material exceeds 9.5% (12 parts by weight), the carbon coating layer becomes excessively thick, which increases the diffusion resistance of lithium ions and may degrade battery performance.

[0048] In a preferred embodiment, the carbon precursor material may include oleic acid and oleilamine. Specifically, the content of each of oleic acid and oleilamine may be 4 to 4.75%. That is, each of oleic acid and oleilamine may be included in a ratio of 5 to 6 parts by weight per 100 parts by weight of silicon active material. In another embodiment of the present invention, the carbon precursor material may include at least one of linoleic acid, linoleylamine, polyvinylpyrrolidone, citric acid, glycerol, dextran, coal tar, and pitch.

[0049] A metal precursor material is used to form metal particles of the aforementioned active material structure. The metal precursor material can be converted into conductive metal particles through a heat treatment process. In this embodiment, the metal precursor material may be tin chloride (SnCl2).

[0050] The content of the metal precursor material may be 7 to 12%. That is, the metal precursor material may be included in a ratio of 9 to 15 parts by weight per 100 parts by weight of the silicon active material. If the amount of metal precursor material added is insufficient, the conductive metal particles formed during the heat treatment process may be insufficient, resulting in a grain size of less than 60 nm. In this case, the size of the metal particles themselves becomes too small, failing to significantly contribute to the improvement of conductivity, and thus the increase in electrical conductivity may be minimal. On the other hand, if the amount of metal precursor material added is excessive, the size of the metal particles may become excessively large, exceeding 80 nm, which prevents them from being well dispersed on the surface of the silicon active material and causes localized aggregation, potentially obstructing the lithium ion diffusion pathway. Furthermore, excessive metal particles may cover the surface of the silicon active particles, thereby reducing charge / discharge efficiency.

[0051] After the mixing of the silicon active material, carbon precursor material, and metal precursor material is completed, purging is performed in a nitrogen atmosphere. Nitrogen purging is a process of controlling the reaction environment or removing impurities using nitrogen (N2) gas during the manufacturing process. Specifically, by replacing the inside of the chamber with nitrogen to remove oxygen from the air, oxidation reactions of silicon and metal are prevented, and a stable atmosphere with low reactivity can be formed using nitrogen, an inert gas. If nitrogen purging is performed for more than 2 hours, the oxygen and moisture content in the reaction space can be reduced to an extremely low level.

[0052] Afterward, the mixture is heated to 380 to 420°C in a nitrogen atmosphere. The mixture is heated at a heating rate of 3 to 7°C / min and can be maintained at that temperature for 2 to 3 hours.

[0053] In the heating step, the carbon precursor material is converted into carbon through thermal decomposition. In this process, the carbon precursor material can be uniformly distributed on the surface of the silicon active particles to form a carbon coating layer with a thickness of 10 to 20 nm. Accordingly, the surface of the silicon active particles is protected and SEI formation can be suppressed. In addition, the volume expansion of the silicon active particles can be physically limited while maintaining the lithium ion diffusion pathway.

[0054] The heating temperature and holding time have a suitable range to ensure the uniformity of the carbon coating layer. Excessive heating can cause non-uniform decomposition of carbon, which may result in irregular thickness and distribution of the carbon coating layer.

[0055] The metal precursor material can be converted into conductive metal particles through reduction or thermal decomposition reactions during heating. The formed metal particles have a grain size of 60 to 80 nm and can be uniformly distributed in some areas within the carbon coating layer.

[0056] Heating temperature and holding time can determine the grain size and distribution of metal particles. At temperatures too low, the formation of metal particles is incomplete, and at excessively high temperatures, the grain size may exceed 80 nm, which can reduce the uniformity of the cathode material.

[0057] Table 1 below shows the results of electrochemical evaluations performed according to the content of conductive metal particles and grain size. The variable is the content of conductive metal particles, and electrochemical evaluations were performed by fabricating half-cells to have identical conditions excluding the aforementioned variable. Grain size was determined by analyzing the diffraction peak (Sn

[0200] peak) corresponding to a specific crystal plane (200) of tin (Sn) based on XRD (X-ray diffraction) data, measuring the full width at half maximum (FWHM), and then...

[0058] It was calculated by substituting into the Scherrer equation. The Scherrer equation is as follows.

[0059] D=βcosθK·λ

[0060] (Here, D: grain size (nm), K: Scherrer constant (usually values ​​between 0.9 and 1 are used), λ: wavelength of X-ray, β: full width at half maximum of diffraction peak (radians), θ: Bragg diffraction angle (half angle of peak position))

[0061] Example 1 involved mixing 100g of silicon active material, 11g of carbon precursor material, and 14.3g of metal precursor material (in weight %, silicon active material 80%, carbon precursor 8.8%, metal precursor material 11.2%). Subsequently, heat treatment was performed up to 400℃ in a nitrogen atmosphere. The carbon precursor material was a mixture to which 5.5g of oleic acid and 5.5g of oleamine were added. The heat treatment conditions were nitrogen purging for 2 hours, a heating rate of 5℃ / min, and a holding time of 3 hours (400℃).

[0062] Example 2 was prepared by fabricating an active material structure under the same conditions as Example 1, with only the amount of metal precursor material added being different. Specifically, 100g of silicon active material, 11g of carbon precursor material, and 9.5g of metal precursor material were mixed (in weight%, silicon active material 83.33%, carbon precursor 9.16%, metal precursor material 7.51%). Subsequently, heat treatment was performed up to 400℃ in a nitrogen atmosphere. The heat treatment conditions were nitrogen purging for 2 hours, a heating rate of 5℃ / min, and a holding time of 3 hours (400℃).

[0063] Comparative Example 1 did not add a metal precursor material. Otherwise, an active material structure was prepared under the same conditions as Example 1. Specifically, 100g of silicon active material and 11g of carbon precursor were mixed (in weight %, silicon active material 90.09%, carbon precursor 9.9%). Subsequently, heat treatment was performed up to 400℃ in a nitrogen atmosphere. The heat treatment conditions were nitrogen purging for 2 hours, a heating rate of 5℃ / min, and a holding time of 3 hours (400℃).

[0064] Comparative Example 2 was prepared by fabricating an active material structure under the same conditions as Example 1, with only the amount of metal precursor material added being different. Specifically, 100g of silicon active material, 11g of carbon precursor material, and 28.5g of metal precursor material were mixed (in weight%, silicon active material 71.94%, carbon precursor 7.92%, metal precursor material 20.14%). Subsequently, the active material structure was fabricated by performing heat treatment up to 400℃ in a nitrogen atmosphere. The heat treatment conditions were nitrogen purging for 2 hours, a heating rate of 5℃ / min, and a holding time of 3 hours (400℃).

[0065] Comparative Example 3 was prepared by fabricating an active material structure under the same conditions as Example 1, with only the amount of metal precursor material added being different. Specifically, 100g of silicon active material, 11g of carbon precursor, and 19g of metal precursor material were mixed (in weight%, silicon active material 77.52%, carbon precursor 8.52%, metal precursor material 13.96%). Subsequently, heat treatment was performed up to 400℃ in a nitrogen atmosphere. The heat treatment conditions were nitrogen purging for 2 hours, a heating rate of 5℃ / min, and a holding time of 3 hours (400℃).

[0066] Afterwards, for each of the active material structures of Example 1 and Example 2 and Comparative Examples 1 to 3, a half cell was prepared by mixing 80 wt% of the active material structure and 20 wt% of the PAA binder in weight%.

[0067] When fabricating the half-cell, the electrolyte composition used was 1 molar concentration lithium hexafluorophosphate (LiPF6), and as the solvent, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7. In addition, 1.0 wt% vinylene carbonate (VC) and 10 wt% fluoroethylene carbonate (FEC) were used as additives.

[0068] The charge-discharge protocol was divided into initial formation charging and general charge-discharge. The initial formation charging stage was performed at a low current density of 0.05C in a voltage range between 0.01V and 1.5V. The purpose of this stage is to form a stable SEI layer on the surface of the cathode material, and the SEI layer controls the reaction between the cathode surface and the electrolyte and is an important factor in determining the Initial Coulombic Efficiency (ICE).

[0069] General charge and discharge tests were performed within a voltage range of 0.01V to 1.0V. The tests began with a current density of 0.1C, and the capacity retention rate and charge / discharge stability of the cathode material were evaluated. To evaluate high-speed charge / discharge characteristics, additional tests were conducted at a current density of 0.5C to verify the effects of conductive metal particles and the carbon coating layer on the electrical and mechanical stability of the silicon active particles. The test results are listed in Table 1.

[0070] Figure 1 is a graph showing the change curves of the electrical capacity retention rate according to the number of charge-discharge cycles of the embodiments listed in Table 1.

[0071] Initial Efficiency (%) Capacity Retention Rate @ 50 cycles Sn Content (%) Sn Grain Size (nm) C Content (%) Comparative Example 1 80.15 6.3--1.66 Comparative Example 2 75.85 4.617.84 116.22 1.83 Example 1 78.669.58.927 4.94 1.67 Example 2 79.166.25.95 60.59 1.79 Comparative Example 3 76.65 3.41 1.89 107.79 1.71

[0072] Referring to Figure 1 and Table 1, it was confirmed that the crystal grain size of the conductive metal particles increased as the amount of added metal precursor material increased. It was also observed that when the crystal grain size became excessively large, it lowered the initial efficiency (ICE) and had a negligible effect on improving cycle stability. Specifically, Comparative Example 1, which did not contain conductive metal particles, showed the highest initial efficiency at 80.1%, but the capacity retention rate after 50 cycles was low at 56.3%. This is attributed to the low electrical conductivity due to the absence of conductive metal particles and the inability to effectively control the volume expansion of the silicon active particles, resulting in reduced long-term stability. In the case of the active material structure of Example 1, the content of conductive metal particles (Sn) was 8.92 wt% and the crystal grain size was 74.94 nm. The electrode material fabricated using the active material structure of Example 1 showed an initial efficiency of 78.6% and a capacity retention rate of 69.5% after 50 cycles, demonstrating the best performance. This is interpreted as a result of conductive metal particles of appropriate size being uniformly distributed within the sulfur material structure, thereby improving electrical conductivity and effectively controlling the volume expansion of silicon active particles.

[0073] In the case of the active material structure of Example 2, the content of conductive metal particles was 5.95 wt% and the grain size was 60.59 nm, and the electrode material fabricated with the active material structure of Example 2 showed an initial efficiency of 79.1% and a capacity retention rate of 66.2%. Although it showed slightly lower performance compared to Example 1, it exhibited generally good electrochemical characteristics.

[0074] On the other hand, in the case of the active material structure of Comparative Example 2, the content of conductive metal particles was excessive at 17.84 wt%, so the grain size increased to 116.22 nm. As a result, the initial efficiency of the electrode material was the lowest at 75.8%, and the capacity retention rate was also poor at 54.6%. The active material structure of Comparative Example 3 also had a high content of conductive metal particles at 11.89 wt%, which increased the grain size to 107.79 nm, and consequently, the performance of the electrode material deteriorated to an initial efficiency of 76.6% and a capacity retention rate of 53.4%.

[0075] Through these results, it was confirmed that the grain size tends to increase as the amount of metal precursor material added increases. On the other hand, it was confirmed that when the amount of metal precursor material added is excessive, the grain size increases to over 100 nm, hindering the diffusion of lithium ions and reducing the volume expansion control effect of silicon active particles, thereby degrading battery performance.

[0076] Therefore, it has been confirmed that the content range of the metal precursor material presented in this invention is a very important factor in optimizing the electrochemical performance of the active material structure for lithium-ion batteries.

[0077] Although embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be made by those skilled in the art to which the disclosed invention belongs without departing from the essence claimed in the claims.

Claims

1. Silicon active particles having a central particle size of 2 to 5 μm; A carbon coating layer surrounding the surface of the above silicon active particle; and It comprises conductive metal particles located in a portion of the carbon coating layer and having a grain size of 60 to 80 nm, and An active material structure for a lithium-ion battery, wherein the content of the conductive metal particles is 5 to 18% by weight.

2. In Paragraph 1, The above conductive metal particles are an active material structure for a lithium-ion battery containing tin (Sn).

3. In Paragraph 1, An active material structure for a lithium-ion battery, wherein the content of the carbon coating layer is 1 to 3% by weight.

4. In Paragraph 1, An active material structure for a lithium-ion battery having a carbon coating layer thickness of 10 to 20 nm.

5. A step of preparing a mixture by mixing a silicon active material containing silicon active particles, a carbon precursor material, and a metal precursor material; and The step of heating the above mixture to 380 to 420°C in a nitrogen atmosphere, and As the above mixture is heated, conductive metal particles are precipitated from the metal precursor material, and A method for manufacturing an active material structure for a lithium-ion battery, wherein the crystal grain size of the precipitated conductive metal particles is 60 to 80 nm.

6. In Paragraph 5, A method for manufacturing an active material structure for a lithium-ion battery, wherein, in the step of manufacturing the above mixture, the metal precursor material is included in a ratio of 9 to 15 parts by weight per 100 parts by weight of the silicon active material.

7. In Paragraph 5, The above conductive metal particles are a method for manufacturing an active material structure for a lithium-ion battery containing tin (Sn).

8. In Paragraph 5, A method for manufacturing an active material structure for a lithium-ion battery, wherein the metal precursor material comprises tin chloride (SnCl2).

9. In Paragraph 5, A method for manufacturing an active material structure for a lithium-ion battery, wherein the carbon precursor material is included in a ratio of 10 to 12 parts by weight per 100 parts by weight of the silicon active material.

10. In Paragraph 5, The above carbon precursor material includes oleic acid and oleamine, and A method for manufacturing an active material structure for a lithium-ion battery, wherein each of the oleic acid and the oleamine is included in a ratio of 5 to 6 parts by weight per 100 parts by weight of the silicon active material.

11. In Paragraph 5, A method for manufacturing an active material structure for a lithium-ion battery, wherein the heating step comprises maintaining the mixture at 380 to 420°C for 2 to 3 hours.

12. In Paragraph 11, A method for manufacturing an active material structure for a lithium-ion battery, wherein in the heating step above, the heating rate is 3 to 7℃ / min.

13. In Paragraph 5, A method for manufacturing an active material structure for a lithium-ion battery, further comprising the step of performing purging in a nitrogen atmosphere for at least 2 hours prior to the heating step.

14. In Paragraph 5, A method for manufacturing an active material structure for a lithium-ion battery, wherein the central particle size of the silicon active particles included in the silicon active material is 2 to 5 μm.

15. In Paragraph 5, In the heating step above, The above silicon active material forms silicon active particles, and The carbon precursor forms a carbon coating layer that coats each of the silicon active particles, and A method for manufacturing an active material structure for a lithium-ion battery, wherein the thickness of the carbon coating layer is 10 to 20 nm.

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