A precursor for a negative electrode active material for lithium secondary batteries, a negative electrode active material containing the same, and a method for producing the same.

Abstract

The present embodiment relates to a negative electrode active material precursor, a negative electrode active material, and a manufacturing method thereof. The negative electrode active material precursor according to the embodiment includes a carbon-based material containing a metal compound and a petroleum-based pitch, and the petroleum-based pitch may include 3 to 10 parts by weight based on 100 parts by weight of the carbon-based material, the softening point of the petroleum-based pitch may be 220 to 280° C., and the content of the metal compound may be 10 ppm or more.

Description

[Technical Field]

[0001] This embodiment relates to a secondary battery, and more specifically, to a negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery containing the same. [Background technology]

[0002] Lithium-ion secondary batteries generally consist of a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator membrane, and an electrolyte, and are charged and discharged by the insertion and decalation of lithium ions. Because lithium-ion secondary batteries have the advantages of high energy density, large electromotive force, and high capacity, they are applied in a wide variety of fields.

[0003] Furthermore, improving high-temperature performance, such as high-temperature storage characteristics and high-temperature cycling characteristics, in lithium secondary batteries is a crucial challenge to address. For example, if the total internal pore volume is high after the negative electrode active material is applied to a current collector and rolled, there is a high probability that the high-temperature performance of the negative electrode will deteriorate. Therefore, it is necessary to improve the high-temperature characteristics when developing negative electrode materials for lithium secondary batteries, such as rapid-charging secondary batteries, by minimizing the changes in electrode structure and the total internal pore volume that occur during electrode rolling.

[0004] Furthermore, as technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source has rapidly increased. Among secondary batteries, lithium-ion batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0005] Furthermore, as concern for environmental issues grows, interest in electric vehicles and hybrid electric vehicles, which can replace fossil fuel vehicles such as gasoline and diesel vehicles—one of the main causes of air pollution—is increasing. Research into using lithium-ion batteries as a power source for electric vehicles and hybrid electric vehicles is actively underway.

[0006] Recently, with the rapid rise of electric vehicles (EVs), expectations for lithium-ion batteries have increased, and there is a growing demand for improvements in fast-charging characteristics while maintaining existing capacity. Improving fast-charging is crucial, and the role of the negative electrode active material, which is responsible for storing lithium ions during charging, is becoming increasingly important.

[0007] As the negative electrode active material, metallic lithium negative electrode active material, carbon-based negative electrode active material, or silicon oxide (SiO₂) x Materials such as the above are used. Carbon-based negative electrode active materials exhibit excellent capacity preservation characteristics and efficiency. Carbon-based negative electrode active materials used as negative electrodes in lithium secondary batteries have a potential close to that of lithium metal electrodes, so the change in crystal structure is small during the insertion and deinsertion processes of ionic lithium. In addition, carbon-based negative electrode active materials enable sustained and repeated oxidation and reduction reactions at the electrode, allowing lithium secondary batteries to exhibit high capacity and excellent lifespan.

[0008] As carbon-based anode active materials, various forms of materials are used, such as crystalline carbon-based materials like natural and artificial graphite, or amorphous carbon-based materials like hard carbon and soft carbon. Among carbon-based anode active materials, graphite-based anode active materials are the most widely used because they offer excellent reversibility and can improve the lifespan characteristics of lithium secondary batteries. Because graphite-based anode active materials have a lower discharge voltage of -0.2V compared to lithium, batteries using graphite-based active materials can exhibit a high discharge voltage of 3.6V, providing a significant advantage in terms of energy density compared to lithium secondary batteries.

[0009] Synthetic graphite, a crystalline carbon-based material, is produced by applying high thermal energy of over 2,700°C to create the graphite crystalline structure. Therefore, it has a more stable crystalline structure than natural graphite, and its crystalline structure changes less even with repeated charging and discharging of lithium ions. Synthetic graphite has the advantage of having a lifespan two to three times longer than natural graphite. Amorphous carbon-based materials, such as soft carbon and hard carbon, which have unstable crystalline structures, have properties that allow lithium ions to penetrate even more smoothly, enabling faster charging and discharging speeds. They can be used in electrodes where high-speed charging is required. Therefore, it is common practice to mix carbon-based materials in a certain ratio, taking into account the lifespan and output characteristics of the lithium secondary battery to be used.

[0010] However, among graphite-based materials used as negative electrode active materials, natural graphite has the problem of low hardness, making a coating treatment essential to impart hardness. However, this coating treatment presents a limitation in the production of high-capacity batteries. [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The technical problem that this invention aims to solve is to provide a negative electrode active material precursor that ensures high hardness and electrical conductivity.

[0012] Another technical problem that the present invention aims to solve is to provide a negative electrode active material having the aforementioned advantages.

[0013] Another technical problem that the present invention aims to solve is to provide a method for producing a negative electrode active material having the aforementioned advantages. [Means for solving the problem]

[0014] The negative electrode active material precursor according to an embodiment of the present invention includes a carbon-based material containing a metal compound and a petroleum pitch. The petroleum pitch contains 3 to 10 parts by weight based on 100 parts by weight of the carbon-based material. The softening point of the petroleum pitch is 220 to 280 °C, and the content of the metal compound may be 10 ppm or more. In one embodiment, the carbon-based material may be at least one of natural graphite, soft carbon, hard carbon, kish graphite, pyrolytic carbon, liquid crystal pitch-based carbon fiber, mesophase graphite powder, carbon microspheres, liquid crystal pitch, and coal-based coke.

[0015] In one embodiment, the carbon-based material may have a purity of 97% or more. In one example, the average particle size D50 of the carbon-based material may be 13 to 17 μm.

[0016] In one embodiment, the beta resin content of the petroleum pitch may be 15 to 40%. In one embodiment, the petroleum pitch may have a residual mass of 50% or less when measured based on 400 °C. In one embodiment, the metal compound may be a compound containing at least one or more metal elements of Fe, Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Co, Ni, Cu, Zn, Ag, Mg, Sr, and Ba, or a mixture thereof.

[0017] The negative electrode active material according to another embodiment includes a carbon-based material containing a metal compound and a petroleum pitch. The petroleum pitch contains 3 to 10 parts by weight based on 100 parts by weight of the carbon-based material. The softening point of the petroleum pitch is 220 to 280 °C, and the content of the metal compound is 10 ppm or more. The negative electrode active material may include a negative electrode active material precursor. In one embodiment, the negative electrode active material can satisfy the following formula 1.

[0018] <Formula 1> ((Span2 - Span1) / Span1)×100 ≦ 15% (In Equation 1 above, Span1 is (D90-D10) / D50 of the negative electrode active material, Span2 is (D90-D10) / D50 of the negative electrode active material after a 1,000 rpm shear force test, and D10, D50, and D90 represent particle sizes corresponding to 10, 50, and 90% of the volume accumulation, respectively, from the smallest particle size side.)

[0019] A method for producing a negative electrode active material precursor according to another embodiment includes the steps of: preparing a carbon-based material containing 10 ppm or more of a metal compound; adjusting the particle size of the carbon-based material to 13 to 18 μm; adding 3 to 10 parts by weight of petroleum-based binder pitch to the carbon-based material based on 100 parts by weight of the carbon-based material; and mixing the carbon-based material and the petroleum-based binder pitch, wherein the softening point of the petroleum-based binder pitch may be 220 to 280°C.

[0020] In one embodiment, the step of adjusting the particle size of the carbon-based material may include a grinding step by at least one of physical impact and airflow impact. In one embodiment, the step of mixing the carbon-based material and the petroleum-based binder pitch may be carried out by applying rotational shear force. [Effects of the Invention]

[0021] According to one embodiment of the present invention, by utilizing a precursor with high hardness, it is possible to provide a negative electrode active material precursor that exhibits high performance even when forming a low coating film, and that allows for the production of a negative electrode material with high discharge capacity derived from natural graphite by utilizing a thin coating film.

[0022] Furthermore, according to another embodiment of the present invention, a negative electrode active material comprising a negative electrode active material precursor having the above-mentioned advantages can be provided.

[0023] Furthermore, according to other embodiments of the present invention, a method for producing a negative electrode active material having the aforementioned advantages can be provided. [Brief explanation of the drawing]

[0024] [Figure 1] Figure 1 is a flowchart of a method for producing a negative electrode active material precursor according to one embodiment of the present invention. [Modes for carrying out the invention]

[0025] The terms First, Second, Third, etc., are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the First part, component, region, layer, or section described below may be referred to as the Second part, component, region, layer, or section, to the extent that it does not fall outside the scope of the present invention.

[0026] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the phrase explicitly indicates otherwise. The meaning of “including” as used in this specification is to embody a particular characteristic, area, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, areas, integers, steps, operations, elements, and / or components.

[0027] When one part is described as being "on top of" or "above" another part, it immediately implies that the other part may be on top of or above the other part, or that the other part may be between them. In contrast, when one part is described as being "directly on top of" another part, it implies that the other part is not between them.

[0028] Unless otherwise specifically defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have the meaning consistent with the relevant technical literature and the present disclosures, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0029] Embodiments of the present invention will be described in detail below. However, these are presented as examples only and do not limit the present invention, which is defined only by the scope of the claims described later.

[0030] A negative electrode active material precursor according to one embodiment of the present invention comprises a carbon-based material containing a metal compound and petroleum-based pitch. The negative electrode active material precursor serves as the base material for the negative electrode active material and is required to have high electrochemical properties for use in secondary batteries.

[0031] The carbon-based material can be a variety of carbon-based materials such as low-crystalline carbon and high-crystalline carbon. The low-crystalline carbon may include at least one of soft carbon and hard carbon, and the high-crystalline carbon may include carbon-based materials such as natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase graphite powder (MGP), meso-carbon microbeads, mesophase pitches, and coal tar-derived coke, as well as carbon-based materials such as artificial graphite, graphitized carbon fiber, and resin-fired bodies. Specifically, the carbon-based material of the present invention may be natural graphite.

[0032] In one embodiment, the carbon-based material may have at least one shape among flakes, spheres, and lumps. Specifically, the carbon-based material may be spherical natural graphite particles.

[0033] In one embodiment, the carbon-based material includes the metal compound. The metal compound may be a compound or mixture thereof containing at least one metal element from among Fe, Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Co, Ni, Cu, Zn, Ag, Mg, Sr, and Ba, and may specifically contain Fe.

[0034] In one embodiment, the carbon-based material may contain 10 ppm or more of the metal compound. When the metal compound is present in 10 ppm or more by weight, an electrical conductivity of 150 s / cm or more can be ensured, allowing it to be used as a negative electrode material. If the content is less than this range, the electrical conductivity is low, making it difficult to apply as a negative electrode material.

[0035] In one embodiment, the carbon-based material may have a purity of 97% or higher. Specifically, the carbon-based material may have a fixed carbon content of 97% or higher. If the purity of the carbon-based material is lower than this, there is a problem that its performance deteriorates due to impurities.

[0036] In one embodiment, the average particle size D50 of the carbon-based material may be in the range of 13 to 17 μm. D50 refers to the particle size corresponding to 50% of the volume accumulation from the smallest particle size. If the average particle size of the carbon-based material falls outside the upper limit of the range, the base material becomes excessively large, limiting the ability to maintain strength due to the limits of the binder pitch coverage. If the average particle size of the carbon-based material falls outside the lower limit of the range, the specific surface area becomes excessively high, requiring an excessive amount of binder pitch, which inevitably leads to a decrease in battery capacity.

[0037] The petroleum-based pitch is included in amounts of 3 to 10 parts by weight, based on 100 parts by weight of the carbon-based material. Specifically, this means that the petroleum-based pitch is included in amounts of an additional 3 to 10 parts by weight, based on extrapolation to the carbon-based material.

[0038] When the content of the petroleum-based pitch falls outside the upper and lower limits of the range, a problem arises when manufacturing a negative electrode material using a negative electrode active material precursor containing the petroleum-based pitch: the rate of increase in the span value of the negative electrode material after a shear force test becomes excessively high. This excessively high rate of increase in the span value leads to the generation of an excessive amount of fine powder, causing the coating layer to peel off and the particles to separate. Specifically, a problem arises where the adhesion between the coating material and the base material surface decreases, resulting in a reduction in the function of the negative electrode active material.

[0039] In one embodiment, the softening point of the petroleum-based pitch is within the range of 220 to 280°C. This softening point being within this range provides the advantage of superior functionality as a negative electrode active material.

[0040] If the aforementioned range is not met, the rate of increase of the span value becomes excessively high, which can lead to problems such as the coating layer peeling off and particles separating.

[0041] In one embodiment, the residual weight of the petroleum-based pitch at 400°C may be 50% or less based on its weight. If the residual weight is greater than 50%, during battery manufacturing, the increase in amorphous carbon structure makes the insertion and removal of lithium ions unfavorable, resulting in a problem of reduced battery efficiency.

[0042] In one embodiment, the petroleum-based pitch may have a beta-resin content of 15 to 40% by weight. The beta-resin can act as an adhesive during the manufacture of the negative electrode material.

[0043] In another embodiment of the present invention, the negative electrode active material is a negative electrode active material for a lithium secondary battery produced by heat-treating the negative electrode active material precursor described above. The negative electrode active material of the present invention satisfies the following formula 1.

[0044] <Expression 1> ((Span2-Span1) / Span1)×100≦15% (In Equation 1 above, Span1 is (D90-D10) / D50 of the negative electrode active material, Span2 is (D90-D10) / D50 of the negative electrode active material after a 1,000 rpm shear force test, and D10, D50, and D90 represent particle sizes corresponding to 10, 50, and 90% of the volume accumulation, respectively, from the smallest particle size side.)

[0045] Span1 may be the span value obtained when the aforementioned negative electrode active material precursor is carbonized to produce the negative electrode active material. The carbonization may be carried out, for example, in a temperature range of 900°C or higher. Span2 may be the change in span value measured after a shear force test is performed on the negative electrode active material.

[0046] If the value of Equation 1 does not meet the above range, there is a problem that excessive fine powder will be generated, causing the coating layer to peel off and the particles to separate. Specifically, there is a problem that the adhesion between the coating material and the base material surface will decrease, reducing its function as a negative electrode active material.

[0047] Figure 1 is a flowchart of a method for producing a negative electrode active material precursor according to one embodiment of the present invention.

[0048] Referring to Figure 1, the process includes the steps of preparing a carbon-based material containing a metal compound (S100), adjusting the particle size of the carbon-based material (S200), adding petroleum-based binder pitch to the carbon-based material (S300), and mixing the carbon-based material and the petroleum-based binder pitch (S400). Detailed descriptions of the carbon-based material, the petroleum-based binder pitch, and the metal compound can be referenced to the extent that they do not contradict the descriptions of the anode active material precursor and the anode active material described above.

[0049] The step of preparing a carbon-based material containing a metal compound (S100) allows for the preparation of a carbon-based material containing 10 ppm or more of the metal compound. The presence of 10 ppm or more of the metal compound makes it suitable for use as a negative electrode material with excellent electrical conductivity.

[0050] The step of adjusting the particle size of the carbon-based material (S200) can adjust the particle size of the carbon-based material to 13 to 18 μm. The step of adjusting the particle size of the carbon-based material (S200) can be controlled by physical impact. The physical impact can be provided by equipment that utilizes physical impact, such as a jet mill, an air classifier mill, or a roller mill. The jet mill directly grinds particles using collisions between particles, the air classifier grinds particles using airflow, and the roller mill grinds particles by feeding, compressing, and grinding them between two or more rollers rotating in opposite directions.

[0051] The step of adding petroleum-based binder pitch to the carbon-based material (S300) may include adding 3 to 10 parts by weight based on 100 parts by weight of the carbon-based material. By satisfying the above range, it is possible to prevent the rate of increase of the span value described above from becoming excessively large.

[0052] The step of mixing the carbon-based material and the petroleum-based binder pitch (S400) can utilize a mixing method such as dry or wet. Specifically, the step of mixing the carbon-based material and the petroleum-based binder pitch (S400) may be carried out by at least one of the following methods: an airflow method, a granulation spheroidization method, and a mechanical milling method.

[0053] The airflow method may involve mixing the wall surface and the negative electrode active material precursor by friction using centrifugal force. The granulation spheroidization method is a method in which crushing and granulation are performed simultaneously, and may include a dry method in which the crushed particles are processed by a blade mill, a multi-purpose mixing mill, or a combination thereof, and a wet method using spray drying. The mechanical milling method is a method in which two or more rollers rotate by friction in the vertical direction, and the carbon-based material and the petroleum-based binder pitch can be milled and mixed.

[0054] The step of mixing the carbon-based material and the petroleum-based binder pitch (S400) may include the step of forming a coating layer. The coating layer may be formed by mixing the carbon-based material and the petroleum-based binder pitch, with the petroleum-based binder pitch coating the surface of the carbon-based material.

[0055] In one embodiment, after mixing the negative electrode active material precursor and the coating material to form the coating layer, shear and / or compressive forces may be applied. The shear and / or compressive forces may be applied to allow the coating material to be positioned on the surface of the negative electrode active material precursor.

[0056] In another embodiment of the present invention, a lithium secondary battery may include a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a separation membrane and electrolyte located between the positive electrode and the negative electrode.

[0057] The positive electrode is LiCoO2, LiNiO2, LiNix Mn y O2, Li 1+z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, LiFeO2, LiFePO4, or any one of the group consisting of combinations thereof, wherein x is from 0.3 to 0.8, y is from 0.1 to 0.45, and z may independently be from 0 to 0.2. More specifically, the positive electrode may be LiFePO4, LiCoO2, NCM811, and NCM622.

[0058] The negative electrode can use a negative electrode active material produced using the aforementioned negative electrode active material precursor, negative electrode active material, or a negative electrode active material precursor produced through a method for producing a negative electrode active material precursor.

[0059] The separator can be used alone or in a laminated form a normal porous polymer film conventionally used as a separator, for example, a porous polymer film made of a polyolefin polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / propylene copolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a normal porous non-woven fabric, for example, a non-woven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, etc. This is a non-limiting example.

[0060] In the electrolyte solution, the lithium salt that can be included as the electrolyte can be used without limitation to those commonly used as an electrolyte solution for a lithium secondary battery. For example, as the anion of the lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4- ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - It may be any one selected from the group consisting of the following.

[0061] In the electrolyte, the organic solvent can be any solvent commonly used in electrolytes for lithium secondary batteries, and typically one or more solvents selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran can be used.

[0062] The lithium secondary battery may be placed inside a battery case. The battery case may be, without limitation, cylindrical, rectangular, pouch-type, or coin-type, using a can. [Examples]

[0063] The embodiments of the present invention will be described below in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be embodied in a variety of different forms and is not limited to the embodiments described herein.

[0064] <Negative electrode active material precursor> The following examples and comparative examples show the electrical conductivity of the negative electrode material based on the iron (Fe) particle content, using natural graphite spheroidal particles, D50 of 16 μm, and density of 1.8 g / cc as a reference at 25°C. Specifically, the iron particle content was measured via ICP (Inductively Coupled Plasma).

[0065] [Table 1]

[0066] As can be seen in Table 1 above, when the iron (Fe) content is 10 ppm or more, it can be confirmed that the electrical conductivity of the negative electrode material is 150 s / cm or more.

[0067] <Negative electrode active material> Table 2 below shows the results of mixing petroleum-based or coal-based pitch based on the negative electrode active material precursor of Example 1 in Table 1, using the method described in Table 2 as a reference, followed by mixing by running the machine dry. The mixed material was then carbonized at 1,000°C for 1 hour to produce the negative electrode active material. The change in span was measured by a shear force test at 1,000 rpm. In this case, the span represents the (D90-D10) / D50 value.

[0068] [Table 2]

[0069] Table 2 shows that when coal-based pitch is used, the span value increases significantly. This increase in span value indicates that a large amount of fine powder is generated, and the generation of this fine powder is due to the peeling of the coating layer, separation of particles, and low adhesion between the coating material and the base material surface. Thus, the low adhesion between the coating material and the base material surface leads to a problem in that the functionality of the negative electrode active material is reduced.

[0070] Looking again at Table 2, when petroleum-based pitch is used, if the pitch content is 2% or 11%, the increase rate of the span value is 15% or more, which presents a problem of reduced functionality as a negative electrode active material.

[0071] As shown in Table 3 below, based on the anode active material precursor of Example 1 in Table 1, petroleum-based pitch or coal-based pitch was mixed using a 5% extrapolation basis, and then mixing was performed by running the mixture dry. After that, the mixed material was carbonized at 1,000°C for 1 hour to produce the anode active material. The change in span was measured by a shear force test at 1,000 rpm. In this case, the span represents the (D90-D10) / D50 value.

[0072] [Table 3]

[0073] As can be seen in Table 3, the coal-based material exhibits a large rate of change in span value regardless of the softening point. This confirms that, when using the coal-based pitch as a base for battery manufacturing, all of them will be peeled off.

[0074] Looking again at Table 3, it can be confirmed that in the case of petroleum-based materials, the span increase rate is 15% or less only in Examples 2 to 4, where the softening point is greater than 210 and less than 280. Comparative Examples 1 and 5 are based on petroleum-based pitch, but because the softening point temperature falls outside the range of the present invention, the span increase rate is greater than 15%, and it can be confirmed that peeling is severe during battery manufacturing.

[0075] <Electrochemical evaluation of lithium secondary batteries> Table 4 below shows the results of thermogravimetric analysis (TGA) of two types of pitch, specifically coal-based and petroleum-based pitch, using weight as the basis and residual weight at 400°C as the basis, when the D50 of spherical natural graphite is 14 μm, the pitch type is petroleum-based pitch, the softening point is 250°C, and the pitch content is 6%.

[0076] Based on the examples and comparative examples listed in Table 4 below, electrochemical evaluations were performed through the following process.

[0077] A negative electrode active material slurry was prepared by mixing 97% by weight of the manufactured negative electrode active material, 2% by weight of a binder containing carboxymethylcellulose and styrene-butadiene rubber, and 1% by weight of Super P conductive material in a distilled water solvent. The negative electrode active material slurry was applied to a copper (Cu) current collector, and then vacuum-dried in a 100°C vacuum oven for 12 hours to produce a negative electrode.

[0078] After vacuum drying, the electrode density of the negative electrode was adjusted to 1.5 to 1.7 g / cc. Since the negative electrode material is included as a component during slurry production, the same series of processes, such as copper (Cu) coating, are applied to all of them.

[0079] The negative electrode manufactured by the above method and lithium metal (Li-Metal) were used as the relative electrode, and the electrolyte was a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1 in which 1 mole of LiPF6 solution was dissolved.

[0080] Using the aforementioned components, a 2032 coin cell type half-cell was manufactured by a conventional manufacturing method.

[0081] [Table 4]

[0082] As seen in Table 4 above, it was confirmed that when the remaining weight exceeds 50%, there is a problem in that the battery efficiency decreases. This is because when the remaining weight is 50% or more, there is a problem that is unfavorable for the insertion and removal of lithium ions due to the increase in amorphous carbon structure.

[0083] The present invention is not limited to the embodiments described above and can be manufactured in a variety of different forms. Those with ordinary skill in the art to which the present invention pertains will understand that the invention can be implemented in other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects.

Claims

1. A carbon-based material which is natural graphite containing a metal, a metal compound, or a mixture thereof, and a petroleum-based pitch, The aforementioned petroleum-based pitch contains 3 to 10 parts by weight of carbon-based material, based on 100 parts by weight of carbon-based material. The softening point of the aforementioned petroleum-based pitch is 220 to 280°C. A negative electrode active material precursor having a content of 10 ppm to 30 ppm of the aforementioned metal, metal compound, or mixture thereof.

2. The carbon-based material has a purity of 97% or more, as described in claim 1, for the anode active material precursor.

3. The negative electrode active material precursor according to claim 1, wherein the average particle size D50 of the carbon-based material is 13 to 17 μm.

4. The anode active material precursor according to claim 1, wherein the beta resin content of the petroleum-based pitch is 15 to 40%.

5. The anode active material precursor according to claim 1, wherein the petroleum-based pitch has a residual mass of 50% or less when measured at a reference temperature of 400°C.

6. The negative electrode active material precursor according to claim 1, wherein the metal, metal compound, or mixture thereof is at least one metal from Fe, Ge, Sn, Pb, Sb, Bi, Al, Ga, In, Ti, Mn, Co, Ni, Cu, Zn, Ag, Mg, Sr, and Ba, a compound containing at least one of these metal elements, or a mixture thereof.

7. A carbon-based material which is natural graphite containing a metal, a metal compound, or a mixture thereof, and a petroleum-based pitch, The aforementioned petroleum-based pitch contains 3 to 10 parts by weight of carbon-based material, based on 100 parts by weight of carbon-based material. The softening point of the aforementioned petroleum-based pitch is 220 to 280°C. A negative electrode active material comprising a negative electrode active material precursor having a content of the aforementioned metal, metal compound, or mixture thereof of 10 ppm to 30 ppm.

8. The negative electrode active material according to claim 7, satisfying the following formula 1. <Formula 1> ((Span ２ -Span １ ) / Span １ )×100≦15% (In the above equation 1, Spa １ This is the (D90-D10) / D50 of the negative electrode active material, and Spa ２ This is (D90 - D10) / D50 after a 1,000 rpm shear force test of the negative electrode active material, where D10, D50, and D90 represent particle sizes corresponding to 10%, 50%, and 90% of the volume accumulation, respectively, from smallest to largest particle size.

9. The steps include preparing a carbon-based material, which is natural graphite, containing 10 ppm to 30 ppm of metal, metal compounds, or mixtures thereof, The steps include adjusting the particle size of the carbon-based material to 13 to 18 μm, The step of adding 3 to 10 parts by weight of petroleum-based binder pitch to the carbon-based material, based on 100 parts by weight of the carbon-based material. The step includes mixing the carbon-based material and the petroleum-based binder pitch, A method for producing a negative electrode active material precursor, wherein the softening point of the petroleum-based binder pitch is 220 to 280°C.

10. The method for producing a negative electrode active material precursor according to claim 9, wherein the step of adjusting the particle size of the carbon-based material includes a grinding step by at least one of physical impact and airflow impact.

11. The method for producing a negative electrode active material precursor according to claim 9, wherein the step of mixing the carbon-based material and the petroleum-based binder pitch is carried out by applying a rotational shear force.

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