Negative electrode material for high-capacity lithium ion battery

Abstract

One aspect of the present invention provides: a negative electrode material for a high-capacity lithium ion battery, which has improved cycle life due to a controllable amount of stabilized zirconia in a Si-carbon composite negative electrode material, thereby preventing a decrease in capacity per weight; and a carbon matrix capable of capturing Si nanoparticles and crystalline carbon is provided.

Description

Technical Field

[0001] The present disclosure relates to a negative electrode material for a high-capacity lithium-ion battery and a method for manufacturing the same. Background Art

[0002] Lithium-ion batteries are currently the most widely used secondary battery systems in portable electronic communication devices, electric vehicles, and even energy storage devices. Compared with commercial aqueous secondary batteries (Ni-Cd, Ni-MH, etc.), such lithium-ion batteries have advantages such as high energy density and working voltage, and relatively low self-discharge rate, and thus are the focus of attention. However, considering more effective usage time in portable devices and improved energy characteristics in electric vehicles, improvement of electrochemical characteristics still exists as a technical problem to be solved. Therefore, research and development are currently being carried out on four main raw materials including a positive electrode, a negative electrode, an electrolyte, and a separator.

[0003] Among these raw materials for the negative electrode, graphite-based materials that exhibit excellent capacity retention characteristics and efficiency have been commercialized. However, the relatively low theoretical capacity value (LiC6: 372 mAh / g) and low discharge capacity ratio of graphite-based materials are slightly insufficient to meet the high energy and high power density characteristics of batteries required in the market.

[0004] Therefore, many researchers are interested in Group IV elements (Si, Ge, Sn) in the periodic table, and among them, in particular, Si is dominant as a very attractive material due to its very high theoretical capacity (Li 15 Si4: 3600 mAh / g) and low working voltage (about 0.1 V relative to Li / Li+). However, Si undergoes large volume expansion and contraction due to the reaction with lithium during charging and discharging, which may lead to fine powder of the silicon active material and poor electrical contact between the silicon active material powder and the current collector. Due to this phenomenon, the capacity of the lithium-ion battery may rapidly decrease as the charge and discharge cycles proceed. Summary of the Invention

[0005] Technical Problem

[0006] One aspect of the present disclosure is to provide a negative electrode material for a high-capacity lithium-ion battery and a method for manufacturing the same, the negative electrode material for a high-capacity lithium-ion battery reducing volume expansion of silicon caused by repeated charging and discharging, having a long cycle life, and having excellent charge and discharge capacity.

[0007] Technical Solution

[0008] According to one aspect of the present disclosure, a negative electrode material for a lithium-ion battery includes: Si nanoparticles; crystalline carbon; a carbon matrix; and zirconia in an amount less than 2.5 wt%.

[0009] The crystalline carbon may include at least one of artificial graphite, flake graphite, amorphous graphite, graphene, coal-based pitch, and petroleum-based pitch.

[0010] The carbon matrix may include carbon derived from at least one of petroleum-based pitch and coal-based pitch having a softening point of 250 °C or lower, coal tar, PAA, and PVA.

[0011] The petroleum-based pitch and the coal-based pitch may have a high β-resin value of 25% or more and a fixed carbon ratio of 70% or more.

[0012] The zirconia may include zirconia derived from a process of nanosizing Si particles.

[0013] The negative electrode material may contain 40 wt% to 65 wt% of Si nanoparticles and less than 50 wt% of crystalline carbon.

[0014] The median particle size of the negative electrode material may be 15 μm or less.

[0015] According to another aspect of the present disclosure, a method for manufacturing a negative electrode material for a lithium-ion battery includes: pulverizing an Si raw material through a mechanical grinding process to obtain Si nanoparticles; mixing crystalline carbon and a carbon matrix precursor with the Si nanoparticles to obtain a mixture; pressing the mixture into a shape to manufacture a block; heating the block in an inert atmosphere at a temperature below 1000 °C; and pulverizing the block, wherein the manufactured negative electrode material may contain less than 2.5 wt% of zirconia.

[0016] The mechanical grinding process may use polycrystalline silicon raw material (polycrystalline Si) having a full width at half maximum of 0.2 degrees or more as a starting material.

[0017] The mechanical grinding may be performed using stabilized zirconia balls having a median particle size (D50) less than twice the D99 particle size of the Si raw material.

[0018] During the mechanical grinding process, the D1 particle size of the stabilized zirconia may be maintained at 52 μm or more.

[0019] The median particle size of the Si nanoparticles may be less than 150 nm.

[0020] The median particle size of the crystalline carbon may be 5 μm or more and 10 μm or less.

[0021] The zirconia may include zirconia derived from the mechanical grinding process.

[0022] The manufactured negative electrode material may contain 40 wt% to 65 wt% of Si nanoparticles and less than 50 wt% of crystalline carbon.

[0023] Beneficial effects

[0024] According to one aspect of the present disclosure, by controlling the content of stabilized zirconia in the Si-carbon composite negative electrode material as described above, a decrease in capacity per weight is prevented, and a carbon matrix capable of capturing Si nanoparticles and crystalline carbon can be provided, thereby providing a negative electrode material for a high-capacity lithium-ion battery with improved cycle life.

[0025] According to another aspect of the present disclosure, a method for manufacturing a negative electrode material for a lithium-ion battery that can easily synthesize the above Si-carbon composite negative electrode material can be provided. Detailed embodiments

[0026] Hereinafter, embodiments of the present disclosure will be described. However, the embodiments of the present disclosure can be modified in various other forms, and the scope of the present disclosure is not limited to the following embodiments. In addition, the embodiments of the present disclosure are provided to more completely describe the present disclosure to those skilled in the art.

[0027] In this specification, unless otherwise specifically stated, the term "comprising / including" is used to indicate that other components may not be excluded, but are included.

[0028] In addition, in the specification of the present disclosure, unless otherwise specifically stated, the % unit represents weight %.

[0029] In order to prevent deterioration of the cycle characteristics caused by volume expansion and contraction of silicon particles, Si nanoparticles must be obtained from a polysilicon raw material (polycrystalline Si) through a Si nanosizing process.

[0030] Such a Si nanosizing process is carried out by a medium having a higher hardness than Si, and stabilized zirconia having high hardness and small volume change at high temperature is generally used. In the corresponding nanosizing process, the stabilized zirconia is collided with Si particles to crush them into nanoparticles of nanosize. The Si nanoparticles finely crushed in this way must be perfectly captured by the carbon matrix so that the Si-carbon composite negative electrode material containing them can ensure long life and low expansion characteristics.

[0031] However, according to the research results of the inventors of the present disclosure, due to the collision between stabilized zirconias during the Si nano-sizing process, fine particles of zirconia are inevitably discharged through the nano-grinding device, and the fine particles of zirconia discharged in this way may be included in the carbon matrix. In this case, due to the high packing density value (6 g / cc) of zirconia, the capacity of the negative electrode material per weight may be reduced. In addition, as the number of particles in the carbon matrix increases, it may be difficult for Si nanoparticles to be captured in the carbon matrix, which may increase the specific surface area of the negative electrode material, thus significantly reducing the cycle life of the negative electrode material.

[0032] Therefore, the inventors of the present disclosure recognized the need to actively limit the content of zirconia in the negative electrode material and arrived at the present disclosure. From this perspective, the negative electrode material according to an embodiment of the present disclosure may include: Si nanoparticles; crystalline carbon; a carbon matrix; and less than 2.5 wt% of zirconia. Hereinafter, each component will be described in detail.

[0033] In an embodiment of the present disclosure, a silicon-based negative electrode material containing Si nanoparticles is targeted. Compared with a carbon-based negative electrode material, the negative electrode material may include Si nanoparticles to achieve a high-capacity battery. In addition, in an embodiment of the present disclosure, the Si nanoparticles may be fine particles having a median particle size (D50) of less than 150 nm. More specifically, the negative electrode material according to an embodiment of the present disclosure may have an upper limit of the silicon particle size of up to 150 nm, such that reversible charge-discharge can be performed without pulverizing the silicon active material powder. The median particle size refers to the particle size at the center of the particle size distribution obtained when measured by a particle size analyzer from Beckmann Coulter.

[0034] The crystalline carbon contained in the negative electrode material may play a role in improving the conductivity of the negative electrode material and enhancing the reversibility of lithium ions, thereby improving the cycle life. At this time, as an example, the crystalline carbon may include at least one of oriented graphite, graphene, and coal-based pitch or petroleum-based pitch containing β resin. More specifically, the graphite may include artificial graphite, flake graphite, amorphous graphite, etc. having excellent reversibility.

[0035] The carbon matrix can play a role in improving the electrochemical properties of the synthesized powder by filling the micropores inside the Si-carbon precursor during press molding after spray drying. Although not limited thereto, the carbon matrix included in the negative electrode material may include carbon derived from at least one of petroleum-based pitch and coal-based pitch, coal tar, PAA, and PVA having a softening point of 250 °C or lower. At this time, the carbon derived from at least one of petroleum-based pitch and coal-based pitch, coal tar, PAA, and PVA having a softening point of 250 °C or lower may refer to carbon formed by carbonization of the above materials. The pitch may have a high β-resin value of 25% or higher and a fixed carbon ratio of 70% or higher. This is to prevent the expansion of Si nanoparticles and ensure a conductive path.

[0036] The above negative electrode material may include less than 2.5 wt% of zirconia. As described above, according to the research results of the inventors of the present disclosure, when the Si-carbon composite negative electrode material includes 2.5% or more of zirconia, due to the high packing density of zirconia, the number of Si nanoparticles per weight in the negative electrode material may decrease, which may cause a problem of reduced battery capacity. Therefore, in the present disclosure, the content of zirconia may be limited to less than 2.5%. A more preferable upper limit is 2.0%, and an even more preferable upper limit is 1.0%. There is no need to specifically limit the lower limit of the zirconia content. Therefore, the zirconia content may also be 0%. However, considering the degree of zirconia inevitably included due to the process, in the examples of the present disclosure, the lower limit of the zirconia content may be set to 0.25%. In this case, the zirconia included in the negative electrode material may be derived from the process of making Si particles nano-sized.

[0037] According to one embodiment, the negative electrode material of the present disclosure may include 40 wt% to 65 wt% of Si nanoparticles and less than 50 wt% of crystalline carbon.

[0038] If the Si nanoparticles are included in an amount greater than 65%, the Si nanoparticles and the crystalline carbon cannot be completely captured in the carbon matrix, and thus there is a problem that the Si nanoparticles may expand during charging and discharging. In this case, the structure of the negative electrode material may collapse, and the cycle life characteristics of the electrode may deteriorate. A more preferable upper limit is 60%, and an even more preferable upper limit is 58%. At the same time, in order to provide a high-capacity Si-carbon composite negative electrode material, preferably, the Si nanoparticles include 40% or more of Si nanoparticles. A more preferable lower limit is 45%, and an even more preferable lower limit is 50%.

[0039] In addition, the crystalline carbon added to impart conductivity and reversibility can be added in a composition of less than 50% by mass because the carbon matrix can effectively capture the crystalline carbon within the corresponding range. A more preferable upper limit is 20%, and an even more preferable upper limit is 18%.

[0040] The median particle size of the negative electrode material according to the present disclosure can be 15 μm or less. If the median particle size of the negative electrode material exceeds 15 μm, the Si content of each particle may increase, and due to the swelling problem of Si particles, the cycle life characteristics may deteriorate.

[0041] The lithium-ion negative electrode containing the Si-carbon composite negative electrode material according to the present disclosure can exhibit high-capacity characteristics and excellent cycle life characteristics. Preferably, the lithium-ion electrode containing the negative electrode material according to the present disclosure can have an initial discharge capacity of 550 mAh / g or more and an initial efficiency of 87% or more.

[0042] Hereinafter, a method for manufacturing a negative electrode material according to the present disclosure will be described.

[0043] The method for manufacturing a negative electrode material according to the present disclosure may include: pulverizing a Si raw material through a mechanical grinding process to obtain Si nanoparticles; mixing the Si nanoparticles with crystalline carbon and a carbon matrix precursor to obtain a mixture; pressing the mixture into a mold to fabricate a compact; performing heat treatment on the compact; and pulverizing the compact.

[0044] In addition, the negative electrode material manufactured by the above manufacturing method may contain less than 2.5% of zirconia.

[0045] At this time, the zirconia contained in the manufactured negative electrode material may be zirconia derived from the mechanical grinding process.

[0046] The mechanical grinding process can use a polysilicon raw material (polycrystalline Si) having a full width at half maximum of 0.2 or more as a starting material. When the full width at half maximum of the polysilicon raw material is 0.2 or more, even if the starting materials have the same slurry viscosity and undergo a similar wet pulverization process, the viscosity of the slurry containing Si nanoparticles may increase. This means that as the full width at half maximum is higher, the efficiency of nanosizing of silicon particles due to grain boundary breakage is higher. Therefore, in the case of using Si particles having a full width at half maximum of 0.2 or more, the time required for the process of nanosizing Si particles can be reduced, which can reduce the amount of fine particles of zirconia balls discharged during the process and also save manufacturing costs. At the same time, when the full width at half maximum is less than 0.2, the time required for the process of nanosizing Si particles may increase, and thus, the amount of fine particles of stabilized zirconia balls may also increase.

[0047] Stabilized zirconia balls can be used for mechanical grinding. In this case, since the zirconia balls can be used in various sizes in the process, they are not limited to the technical content. However, as an example of an embodiment, the median particle size of the zirconia beads can be less than twice the D99 of the introduced raw material. This is because if the D99 of the introduced raw material is too large or the stabilized zirconia balls are too small, the efficiency of the Si nano-sizing process may be excessively reduced, which may increase the time required for nano-sizing, and thus, side effects such as excessive generation of stabilized zirconia fine particles or oxidation of Si particles may occur.

[0048] In addition, based on D1, the stabilized zirconia particle size during mechanical grinding can be maintained at 52 μm or more. D1 represents the particle size corresponding to the lower 1% of the particle size distribution obtained when measured by a particle size analyzer from Beckmann Coulter. If D1 is less than 52 μm, the fine particles of stabilized zirconia may pass through the sieve of the nano-grinding device and flow out of the corresponding device in large quantities, resulting in an excessive inclusion of stabilized zirconia in the carbon matrix. To prevent this, the stabilized zirconia particle size corresponding to D1 can be set to 52 μm or more.

[0049] In addition, an organic solvent such as ethanol or IPA can be used in the mechanical grinding process to prevent the oxidation of Si.

[0050] In addition, the median particle size of the Si nanoparticles prepared by the above Si nano-sizing process can be less than 150 nm. This is because, as described above, the critical size (Dc) for reversible charge-discharge without pulverizing the silicon active material powder is about 150 nm.

[0051] After pulverization, crystalline carbon and a carbon matrix precursor can be mixed with the Si nanoparticles.

[0052] As described above, the crystalline carbon used in the above manufacturing method can include at least one of graphite, graphene, and coal- or petroleum-based pitch containing β-resin, and preferably can include artificial graphite, flake graphite, amorphous graphite, etc. with excellent reversibility.

[0053] As an example, graphite with a median particle size of 5 μm to 10 μm can be used as the crystalline carbon. If the median particle size of the graphite is less than 5 μm, the number of particles contained in the carbon matrix may relatively increase, so the content of the carbon matrix precursor surrounding the graphite must increase, and thus, the Si content may inevitably decrease relatively, making it difficult to achieve the designed capacity. At the same time, if the median particle size of the graphite exceeds 10 μm, the graphite cannot be positioned inside the Si-carbon precursor, which may deteriorate the performance of the final product.

[0054] In addition, as described above, the carbon matrix precursor may be at least one of petroleum-based pitch, coal-based pitch, coal tar, PAA, and PVA having a softening point of 250 °C or lower, and the pitch used in the manufacturing method may have a high β-resin value of 25% or more and a fixed carbon ratio of 70% or more as described above. Such a carbon matrix precursor may be added to electrically connect and physically connect the Si nanoparticles and the crystalline carbon, and the cohesion between the three raw materials may be improved by forming an amorphous carbon layer via subsequent pressing and heat treatment processes.

[0055] The mixing of the Si nanoparticles, the crystalline carbon, and the carbon matrix precursor may be carried out by a grinding process such as mechanical fusion and ball milling using a powder contact medium. In this way, since the grinding process is carried out using a powder contact medium, the independent flow of the Si nanoparticles can be minimized when mixed with a solvent.

[0056] After the above mixing, the mixture may be pressed into a block. By pressing, the pores present inside the Si nanoparticle-crystalline carbon precursor can be minimized, and a high-density negative electrode material can be manufactured by increasing the cohesion of the constituent particles. The pressure and the pressing time in the pressing operation are not particularly limited within the range that can achieve the above object. In one preferred embodiment, the pressing may be carried out at a pressure of less than 1 ton / cm 2 ².

[0057] Thereafter, the present disclosure may include heating the pressed block in an inert atmosphere at a temperature below 1000 °C. When heated at 1000 °C or higher, a final product inert to lithium ions can be manufactured, so the heat treatment temperature is set below 1000 °C. In addition, the heat treatment may be carried out in an inert atmosphere to prevent the oxidation of the Si nanoparticles.

[0058] After the above heat treatment, the heat-treated block may be pulverized. The pulverization may be carried out using a JET mill, a needle mill, etc., and a final product having a median particle size of 15 μm or less can be obtained thereby.

[0059] Meanwhile, in one embodiment of the present disclosure, it may further include coating the surface of the pulverized particles after pulverization. By additional coating, the surface of the partially exposed Si can be protected to suppress side reactions with the electrolyte. Therefore, the expansion of the Si nanoparticles can be prevented, and excellent electrical properties of the negative electrode material can be ensured.

[0060] In addition, the surface coating may be carried out using petroleum-based pitch or coal tar having a softening point below 250 °C, PAA, PVA, etc.

[0061] Meanwhile, the negative electrode material manufactured as described above may contain 40 wt% to 65 wt% of Si nanoparticles and less than 50 wt% of crystalline carbon.

[0062] Embodiments of the Invention

[0063] (Examples)

[0064] (1) Preparation of a slurry containing Si nanoparticles

[0065] To prepare Si nanoparticles, polycrystalline silicon raw materials having the particle size and grain size shown in Table 1 were ball-milled (which is one of the wet nanosizing processes). In this experiment, the grinding process was started first using new zirconia balls, and samples were collected according to the elapsed time of the grinding process. At this time, the measured values (D1, D50, D90, and distribution width value ((D90 - D10) / D50)) of the stabilized zirconia particle size according to the elapsed time of the grinding process are shown in Table 2 below. The full width at half maximum of the polycrystalline silicon raw material is 0.2 degrees or more, and the median particle size of the Si nanoparticles manufactured by this process is 100 nm. In addition, anhydrous ethanol with 99.9% purity as the solvent and a solid solution ratio of 8% to 15% were used for the wet nanosizing process. In the above process, the ball per ratio (BPR) of the raw material to the stabilized zirconia balls was 5:1, and the rotational speed of the rotor inside the grinder was maintained at 2500 rpm.

[0066] (2) Preparation of the negative electrode material

[0067] 53% of the slurry manufactured according to the corresponding process was mixed with 18% of graphite particles using a high-speed mixer and spray-dried to synthesize a nano Si-graphite precursor with a median particle size of about 8 μm. The above percentages are based on the final Si-graphite composite negative electrode material. The median particle size of the graphite is 5 μm to 10 μm. Then the precursor and pitch powder were mixed. The mixing was carried out by a mechanical fusion process. The mixed nano Si-graphite precursor and pitch powder were placed in a mold with a specific size and uniaxially pressed at a pressure of about 50 tons. The block obtained by the above pressing was heat-treated in an inert atmosphere at a temperature below 1000 °C and pulverized using a JET mill to a median particle size of less than 15 μm. Thereafter, 5% to 10% of coal tar relative to the added Si nanoparticles was added, stirred using a spiral blade mixer for about 30 minutes, heat-treated in an inert atmosphere at a temperature below 1000 °C, and the final Si-carbon composite negative electrode material was obtained through a #635 mesh (20 μm) sieve.

[0068] The content of stabilized zirconia in the obtained final Si-carbon composite negative electrode material was measured and shown in Table 2.

[0069] (3) Electrochemical Evaluation

[0070] For the analysis of electrochemical properties, the synthesized Si-carbon composite anode active material was mixed with 79% commercial natural graphite to fabricate a coin half-cell with a negative electrode capacity of 630 mAh / g. The composition of the negative electrode was active material: conductive material: CMC: SBR = 96.1:1:1.7:1.2. The thickness of the electrode was fixed at 60 μm to maintain the same volume ratio, and the roll pressing density was maintained at 1.6 g / cc. The effective area of the electrode was measured using a diameter of 14 mm. The electrolyte for the life test was EC: EMC = 3:7 (1.0 M LiPF6) + 1.5 wt% VC. The current during charge-discharge at 0.1C in the initial cycle was measured. In addition, based on the first 1C capacity, a current of 0.5C was applied during charge-discharge, and the life of 50 cycles was measured. At this time, the charge cut-off current was set to 0.005C.

[0071] Table 3 shows the electrochemical properties (initial discharge capacity and initial efficiency) of the negative electrode fabricated in this way and the zirconia content contained in the Si-carbon composite negative electrode material.

[0072] [Table 1]

[0073]

[0074]

[0075] [Table 2]

[0076]

[0077] [Table 3]

[0078]

[0079]

[0080] The particle size and grain size of the polysilicon raw material in Table 1 above were measured using XRD, and the zirconia content in the Si-carbon composite negative electrode materials in Table 2 and Table 3 above was measured using icp-aes of SpectroARCO.

[0081] Through the above experiments, the correlation between the content of stabilized zirconia incorporated into the negative electrode material during the process of making Si particles nano-sized, the raw materials for the Si-carbon composite negative electrode material, and the performance of the Si-carbon composite negative electrode material can be determined.

[0082] As shown in Table 2, it can be seen that as the Si nanosizing process proceeds, the content of zirconia in the Si-carbon anode material increases, and at the same time, the particle size of stabilized zirconia decreases. This is because as the time of the Si nanosizing process increases, fine particles of zirconia are generated due to the collision between stabilized zirconia spheres, and they are incorporated into the carbon matrix of the anode material.

[0083] In addition, it can be seen that as the grinding process time increases from 61,440 minutes to 150,720 minutes, and the zirconia content in the anode material exceeds 2.5 wt%, the particle size of the zirconia spheres corresponding to D1 rapidly decreases. Therefore, it can be seen that when the particle size of the zirconia spheres corresponding to D1 is less than 52 μm, it becomes more difficult to prevent the leakage of fine zirconia particles from the nanogrinding device during the Si nanosizing process, and thus a relatively large amount of zirconia is included in the carbon matrix. Even when the grinding process is carried out for a long time, there is no significant difference in the particle size of zirconia corresponding to D1 in Comparative Examples 1 to 3, which is considered to be because a large number of fine particles smaller than 50 μm (which is the screen size of the nanogrinding device) escape from the screen.

[0084] In Comparative Examples 1 to 3, as the Si nanosizing process proceeds, fine particles of stabilized zirconia are excessively introduced into the Si-carbon anode material, and the zirconia content in the anode material exceeds 2.5%. Therefore, the initial discharge capacity and initial efficiency of Comparative Examples 1 to 3 are significantly reduced. This was confirmed by the fact that when the anode material contains zirconia with a large bulk density, the capacity decreases due to the reduction in the amount of Si nanoparticles available per unit weight. In addition, the initial efficiency and capacity generally decrease as the carbon layer becomes thicker. In the case of Comparative Examples 1 to 3, as the amount of Si nanoparticles available per unit weight decreases, the content of pitch, which is the starting material for the carbon matrix, relatively increases within the particles, and the carbon layer becomes thicker. Therefore, the initial efficiency and initial discharge capacity decrease.

[0085] At the same time, since the corresponding zirconia content in Inventive Examples 1 to 3 is less than 2.5%, it is determined that the negative electrode battery exhibits excellent cycle life and high capacity.

Claims

1. A negative electrode material for a lithium-ion battery, the negative electrode material comprising: Si nanoparticles; Crystalline carbon; A carbon matrix; and Zirconia in an amount less than 2.5% by weight.

2. The negative electrode material for a lithium-ion battery according to claim 1, wherein the crystalline carbon comprises at least one of artificial graphite, flake graphite, amorphous graphite, graphene, coal-based pitch, and petroleum-based pitch.

3. The negative electrode material for a lithium-ion battery according to claim 1, wherein the carbon matrix comprises carbon derived from at least one of petroleum-based pitch and coal-based pitch having a softening point of 250 °C or lower, coal tar, PAA, and PVA.

4. The negative electrode material for a lithium-ion battery according to claim 3, wherein the petroleum-based pitch and the coal-based pitch have a high β-resin value of 25% or more and a fixed carbon ratio of 70% or more.

5. The negative electrode material for a lithium-ion battery according to claims 1 to 4, wherein the zirconia comprises zirconia derived from the process of nanosizing Si particles.

6. The negative electrode material for a lithium-ion battery according to claims 1 to 4, wherein the negative electrode material comprises 40% to 65% by weight of the Si nanoparticles and less than 50% by weight of the crystalline carbon.

7. The negative electrode material for a lithium-ion battery according to claims 1 to 4, wherein the median particle size of the negative electrode material is 15 μm or less.

8. A method for manufacturing a negative electrode material for a lithium-ion battery, the method comprising: Crushing Si raw material through a mechanical grinding process to obtain Si nanoparticles; Mixing crystalline carbon and a carbon matrix precursor with the Si nanoparticles to obtain a mixture; Pressing the mixture into a compact to manufacture a block; Heating the block in an inert atmosphere at a temperature below 1000 °C; and Crushing the block, wherein the negative electrode material comprises zirconia in an amount less than 2.5% by weight.

9. The method for manufacturing a negative electrode material for a lithium-ion battery according to claim 8, wherein the mechanical grinding process uses polycrystalline silicon raw material (polycrystalline Si) having a full width at half maximum of 0.2 degrees or more as a starting material.

10. The method for manufacturing a negative electrode material for a lithium-ion battery according to claim 8, wherein the mechanical grinding is carried out using stabilized zirconia balls having a median particle size (D50) less than twice the D99 particle size of the Si raw material.

11. The method for manufacturing a negative electrode material for a lithium-ion battery according to claim 8, wherein during the mechanical grinding process, the D1 particle size of the stabilized zirconia is maintained at 52 μm or more.

12. The method for manufacturing a negative electrode material for a lithium-ion battery according to claim 8, wherein the median particle size of the Si nanoparticles is less than 150 nm.

13. The method for manufacturing a negative electrode material for a lithium-ion battery according to claim 8, wherein the crystalline carbon comprises at least one of artificial graphite, flake graphite, amorphous graphite, graphene, coal-based pitch, and petroleum-based pitch.

14. The method for manufacturing a negative electrode material for a lithium ion battery according to claim 8, wherein the carbon matrix precursor is at least one of petroleum-based pitch and coal-based pitch, coal tar, PAA, and PVA having a softening point of 250 °C or lower.

15. The method for manufacturing a negative electrode material for a lithium ion battery according to claim 8, wherein the zirconia includes zirconia derived from a mechanical grinding process.

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