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

Abstract

To provide a negative electrode active material for a lithium secondary battery manufactured without including a granulation process, a method for manufacturing the same, and a secondary battery including the same.SOLUTION: The present invention provides a manufacturing method of a negative electrode active material for a lithium secondary battery, comprising the steps of: preparing artificial graphite; mixing the artificial graphite and a coal tar to form a coating layer on the artificial graphite; and carbonizing the artificial graphite on which the coating layer is formed, wherein the artificial graphite contains 30 wt.% or more of artificial graphite derived from coal-based coke. The present invention also provides a negative electrode active material manufactured by the method, and a lithium secondary battery including the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates 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. Specifically, the present invention relates to a lithium secondary battery having excellent electrode adhesion and battery performance. Negative electrode active material for lithium secondary batteries, its manufacturing method and lithium secondary batteries containing the same is. [Background technology]

[0002] The graphite / carbon-based negative electrode active material used as the negative electrode of lithium secondary batteries is lithium metal. Since the potential is close to the electrode potential of The change in the crystal structure during oxidation and reduction is small. Therefore, the electrode can undergo continuous and repeated oxidation and reduction reactions. This allows the lithium secondary battery to exhibit high capacity and excellent life.

[0003] The carbon-based negative electrode active material includes crystalline carbon-based materials such as natural graphite and artificial graphite, or amorphous graphite. Various types of carbon-based materials are used, including hard carbon and soft carbon. Among them, graphite has excellent reversibility and can improve the life characteristics of lithium secondary batteries. Graphite-based active materials are the most widely used. Graphite-based active materials have a discharge voltage of -0. Because the discharge voltage is low at 2V, batteries using graphite-based active materials can exhibit a high discharge voltage of 3.6V. This provides many advantages over lithium secondary batteries in terms of energy density.

[0004] Artificial graphite, a crystalline carbon material, is produced by applying high thermal energy of 2,700°C or more to the graphite It has a more stable crystalline structure than natural graphite, allowing for the repetition of lithium ions. The change in the crystal structure is small even during repeated charging and discharging, and the lifespan is relatively long. The material has a lifespan that is about two to three times longer than natural graphite.

[0005] Soft carbon and hard carbon are amorphous carbon-based materials whose crystal structure is not stabilized. The carbon has the property that lithium ions can penetrate more easily. This can increase the charging rate and can be used for electrodes that require high-speed charging.

[0006] Considering the life characteristics and output characteristics of the lithium secondary battery to be used, It is common to use a mixture of the materials in a certain ratio.

[0007] On the other hand, in lithium secondary batteries, high-temperature performance (high-temperature storage characteristics and high-temperature cycle characteristics) After applying the negative electrode active material to the current collector and rolling it, However, if the total internal pore volume is high, the high-temperature performance of the negative electrode is likely to decrease. The structural changes of the electrode and the change in the total internal pore volume that occur during electrode rolling are minimized to prevent lithium ion batteries from being damaged. It is necessary to improve the high-temperature characteristics of secondary batteries.

[0008] In particular, when developing negative electrode materials for fast-charging secondary batteries, improvement of high-temperature properties is most required. .

[0009] Technological developments and increasing demand for mobile devices are driving the adoption of The demand for secondary batteries is increasing rapidly, and among such secondary batteries, high energy Lithium secondary batteries that exhibit high density, high operating potential, long cycle life, and low self-discharge rates are commercially available. It has been standardized and is widely used.

[0010] In addition, as interest in environmental issues grows, air pollution, which is one of the main causes of air pollution, You can transfer vehicles that use fossil fuels such as gasoline and diesel vehicles. There is growing interest in electric vehicles and hybrid electric vehicles. Research and development into the use of lithium secondary batteries as a power source for electric vehicles, hybrid electric vehicles, etc. Research is being actively carried out.

[0011] A lithium secondary battery generally comprises a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and It consists of a silicon dioxide and an electrolyte, and is capable of lithium ion intercalation and deintercalation. It is a secondary battery that is charged and discharged by intercalation. The lithium secondary battery has a high energy density and a large electromotive force. It has the advantage of being large and capable of delivering high capacity, so it is used in a variety of fields.

[0012] In particular, with the recent rapid rise of electric vehicles, expectations for lithium-ion secondary batteries are also increasing. There is an increasing demand for improved fast charging characteristics while maintaining existing capacity. This improvement in fast charging is due to the negative electrode active material, which is responsible for storing lithium ions during charging. The part that must fulfill this role is made up of mainly carbon / graphite-based materials. , stable SEI (solid electrolyte interface) during charging ) is important.

[0013] Here, from the viewpoint of fast charging and lifespan (stability), However, as artificial graphite is used, this trend is expected to continue in the future.

[0014] To obtain artificial graphite, coke particles and binder materials are mixed and heat treated. It is difficult to build equipment to collect the secondary particles, and in actual practice, a certain amount of contamination is Since there are always problems such as contamination, it is difficult to guarantee uniformity in terms of quality realization by location. Therefore, it is necessary to proceed with the minimum number of steps. Summary of the Invention [Problem to be solved by the invention]

[0015] One embodiment is a negative electrode active material for a lithium secondary battery that is manufactured without a granulation process, The present invention provides a manufacturing method and a secondary battery including the same.

[0016] In one embodiment, a lithium secondary battery is manufactured using coal tar without a granulation process. The present invention provides a negative electrode active material for a battery, a method for producing the same, and a secondary battery including the same. [Means for solving the problem]

[0017] According to one embodiment, a method for producing a negative electrode active material for a lithium secondary battery includes preparing artificial graphite. and mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite. and carbonizing the artificial graphite on which the coating layer is formed, The synthetic graphite has a sphericity of 0.6 to 1.

[0018] In the step of preparing the artificial graphite, the artificial graphite is obtained by dividing the artificial graphite derived from coal-based coke into two Contains 0% by weight or more.

[0019] In the step of preparing the artificial graphite, the particle size is 6 μm to 10 μm based on the total volume of the artificial graphite. The volume of artificial graphite with a particle size of 34 μm is 70% or more by volume.

[0020] In the step of preparing the artificial graphite, the particle size of the artificial graphite is 5 μm to 10 μm. The sphericity of artificial graphite is 0.55 or more.

[0021] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In the present invention, the coal tar is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of artificial graphite. It is something.

[0022] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In this study, the coal tar contained quinoline insolubles (QI) in an amount of 1 part by weight relative to the total weight of the coal tar. % to 7% by weight.

[0023] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In this case, the amount of fixed carbon in the coal tar is 10 to 30% by weight based on the total weight of the coal tar. %.

[0024] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In this case, the coal tar has a light oil content of 30% by weight or more based on the total weight of the coal tar. Below.

[0025] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In this study, the coal tar contained 50% toluene insoluble matter (TI) relative to the total weight of the coal tar. % by weight or less.

[0026] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In this case, the beta resin content of the coal tar is 50% by weight of the total weight of the coal tar. % or less.

[0027] The steps of preparing the artificial graphite include crushing coke; and graphitizing the coke. The coke is a coal-based coke or a mixture of a coal-based coke and a petroleum-based coke. The mixture of coal-based coke and petroleum-based coke is a mixture of coal-based coke and petroleum-based coke by weight. Contains 20% by weight or more of coke.

[0028] The step of crushing the coke includes adjusting the sphericity of the crushed coke.

[0029] According to one embodiment, the negative electrode active material for a lithium secondary battery is a material comprising artificial graphite and the artificial graphite surface. The artificial graphite has a coal tar-derived carbon coating layer formed on its surface, and the sphericity of the artificial graphite is It is between 0.6 and 1.

[0030] The artificial graphite contains 20% by weight or more of coal-based coke-derived artificial graphite.

[0031] The coal tar carbon coating layer is formed by mixing 1 to 20 parts by weight of the coal tar carbon based on 100 parts by weight of the artificial graphite. Parts by weight are included.

[0032] The coal tar has a quinoline insoluble content (QI) of 1 wt. % to 7% by weight.

[0033] The coal tar has a fixed carbon content of 10 to 30% by weight based on the total weight of the coal tar. is.

[0034] The coal tar has a light oil content of 30% by weight or less based on the total weight of the coal tar. is.

[0035] The coal tar contains 50% by weight of toluene insoluble matter (TI) relative to the total weight of the coal tar. The amount is less than %.

[0036] The coal tar has a beta resin content of 50% by weight based on the total weight of the coal tar. The following is the result.

[0037] According to one embodiment, the lithium secondary battery further comprises: The present invention includes a negative electrode including a negative electrode active material prepared from the above, a positive electrode, and an electrolyte. [Effects of the Invention]

[0038] A negative electrode active material for a lithium secondary battery according to one embodiment, a method for manufacturing the same, and a battery including the same The secondary battery uses coal tar, a liquid coating material, and does not require a separate granulation process.

[0039] A negative electrode active material for a lithium secondary battery according to one embodiment, a method for manufacturing the same, and a battery including the same The secondary battery has excellent electrode adhesion.

[0040] A negative electrode active material for a lithium secondary battery according to one embodiment, a method for manufacturing the same, and a battery including the same The battery does not require a separate granulation process, so it provides an artificial graphite negative electrode active material made up of single particles. It is possible. DETAILED DESCRIPTION OF THE INVENTION

[0041] Terms such as first, second and third refer to various parts, components, regions, layers and / or sections. The terms are used to describe, but are not limited to, certain parts, components, To distinguish an area, layer, or section from other parts, components, areas, layers, or sections Therefore, the first part, component, region, layer or section described below The embodiment may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention. It can be done.

[0042] The terminology used herein is merely to refer to particular embodiments and is not intended to limit the scope of the present invention. As used herein, the singular forms "a," "an," and "the" are used interchangeably unless the terms clearly state otherwise. Unless the meaning indicates otherwise, the plural form "includes" is also included. It embodies properties, domains, integers, steps, operations, elements and / or components and other properties, domains, It does not exclude the presence or addition of integers, steps, operations, elements and / or components.

[0043] When one part is said to be "on" or "above" another, this immediately refers to the other. It may be on or above a part of, or may have other parts in between. In contrast, when we say that one part is "directly on top of" another part, it means that the other part is in between. Not intervened.

[0044] Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. do.

[0045] In one embodiment of the present invention, further containing an additional element means an additional amount of the additional element. This means that the remaining amount is converted to iron (Fe).

[0046] All technical and scientific terms used herein, including but not limited to, but not limited to: The terms have the meanings commonly understood by those skilled in the art to which this invention pertains. The terms defined in commonly used dictionaries have the same meaning as those in the related technical literature and the present invention. Unless otherwise construed and defined, the terms and conditions of the present disclosure shall have a meaning consistent with the present disclosure. It is not interpreted in a very formal sense.

[0047] The following description of the embodiments of the present invention is provided to those skilled in the art. However, the present invention may be practiced in a variety of different ways. The present invention can be implemented in various forms and is not limited to the embodiments described herein.

[0048] Each step will be described in detail below.

[0049] According to one embodiment, a method for manufacturing a negative electrode active material for a lithium secondary battery includes preparing artificial graphite. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; and carbonizing the artificial graphite on which the coating layer is formed.

[0050] In the method for manufacturing a negative electrode active material for a secondary battery, the step of preparing artificial graphite comprises using coke and graphitizing the coke.

[0051] In addition, in the step of crushing coke in the step of preparing artificial graphite, the coke is crushed into stone. It is a coal-based coke or a mixture of coal-based coke and petroleum-based coke.

[0052] The mixture of coal-based coke and petroleum-based coke contains coal-based coke in an amount of 100% by weight based on the total weight of the mixture. Specifically, the coal-based coke may contain 30% by weight or more of coke. up to 100% by weight, or 40% to 100% by weight, or 60% to 100% by weight %, or 70% to 100% by weight.

[0053] Therefore, in the step of preparing the artificial graphite, the artificial graphite is made from coal-based coke. It can contain 30% by weight or more of artificial graphite. Specifically, it can contain artificial graphite derived from coal-based coke. 30% to 100% by weight, or 40% to 100% by weight, or 60% by weight or more It may be present in an amount up to 100% by weight, or between 70% and 100% by weight.

[0054] In the step of crushing coke in the step of preparing the artificial graphite, coal-based coke or or petroleum coke, respectively, green coke, calcined coke, or a mixture thereof Each coke may be needle coke, isotropic coke, or any of these. It can be a mixture of:

[0055] As the coal-based coke, a mixture of coal-based green coke and coal-based calcined coke was used. When using green coke, the content of green coke must be 20% by weight or more based on the total weight of the mixture. Specifically, it can be 20 to 100% by weight. Volatile Matter content is generally 5 to 10% by weight. If the coating material contains less than 20% by weight of carbon-based green coke, the coating material may be Therefore, the problem of poor wettability with coal may occur, resulting in poor caking properties. When a mixture of coal-based green coke and coal-based calcined coke is used as the coke, It is preferable that the coal-based green coke falls within the above range.

[0056] In addition, the artificial graphite according to the present invention is not a granulated product. The particles themselves are not granulated, and are used as raw materials in the negative electrode active material manufacturing method. Artificial graphite does not include soft carbon adhesives or hard carbon adhesives.

[0057] The method of crushing the coke in the step of preparing the artificial graphite is There is no limitation on the grinding method as long as it can adjust the particle size described below. For example, Jet mill l, Pin mill, Air classifier mill, Raymond m Mill, Jaw crusher, Vertical roller mill, etc. The crushed coke can be classified into the desired particle size using a vibrating sieve. It is possible.

[0058] The step of crushing the coke may include a step of adjusting the sphericity of the crushed coke. The step of adjusting the sphericity is not limited if a means for controlling the sphericity is used. In particular, a means for controlling sphericity by friction using centrifugal force can be used.

[0059] In the step of preparing the artificial graphite, the sphericity of the crushed coke is adjusted to prepare the artificial graphite. The sphericity of the lead can be controlled. In this case, the artificial graphite provided has a sphericity of 0.6 or more. The sphericity of the artificial graphite may be 0.6 to 0.9, or 0.6 to 1. If the sphericity is less than 0.6, the coal tar can easily dissolve the artificial graphite. Since it is impossible to coat the entire surface, some parts are left uncoated. On the other hand, if the sphericity approaches 1, The closer it gets to a perfect sphere, the lower the electrical conductivity becomes. It is possible.

[0060] In addition, the sphericity of the artificial graphite having a particle size of 5 μm to 10 μm is 0.55 or more. Specifically, the sphericity of artificial graphite with a particle size of 5 μm to 10 μm is , 0.55 to 1 or 0.55 to 0.8. When the sphericity of the artificial graphite in the elementary particle region is controlled within the above range, the occurrence of side reactions can be controlled. can.

[0061] In the step of preparing the artificial graphite, the particle size is 6 μm to 10 μm based on the total volume of the artificial graphite. The volume of 34 μm artificial graphite may be 70% or more by volume. When the volume of the graphite satisfies the above range, the electrode adhesion is good.

[0062] In the step of graphitizing the coke in the step of preparing the artificial graphite, the graphitization temperature is 2 The temperature is 200 to 3300°C, and the graphitization treatment time is 3 hours or more.

[0063] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In this case, the artificial graphite and coal tar are mixed by rotating two or more rotating bodies vertically or horizontally. It can be carried out by a means for advancing and mixing, for example, a horizontal sigma blade type. The mixing step may include mixing the artificial graphite and the coal tar using a kneader. The mixing time may be longer than 5 minutes depending on the viscosity of the coal tar used. and mixing speed (rpm) were controlled to ensure that the coal tar coating was uniform on the artificial graphite. It can be done like this.

[0064] mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; In the present invention, the coal tar is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of artificial graphite. Specifically, the coal tar can be used in an amount of 5 to 20 parts by weight based on 100 parts by weight of artificial graphite. The coal tar content may be in the range of 5 to 10 parts by weight. If the above range is not met, the electrode adhesive strength of the negative electrode active material will be insufficient for use in the product. High adhesive strength (e.g., 300gf / cm 2 Below are some questions that show:

[0065] The coal tar has a quinoline insoluble content (QI) of 1 wt. % to 7% by weight. Specifically, the coal tar has a quinoline insoluble content (QI) of 2% to 7% by weight or 2% to 5% by weight based on the total weight of coal tar If the quinoline insoluble content is high, the electrode may deteriorate after being manufactured into a negative electrode material. There could be problems.

[0066] In addition, the coal tar contains toluene insolubles (TI) in a ratio of the total weight of the coal tar to the total weight of the coal tar. Specifically, the toluene insoluble matter (TI) may be 50% by weight or less of the total weight of the coal tar. It may be 10 to 50% by weight or 30 to 40% by weight.

[0067] The beta resin content of the coal tar is 50% by weight of the total coal tar. % by weight or less. Specifically, the beta resin content is 100% by weight or less of the total weight of the coal tar. The beta resin content may be 10 to 50% by weight or 30 to 40% by weight. The key factor that determines the adhesive performance of the negative electrode active material is the addition of beta resin to coal tar. If the content is too high, there may be a problem that the adhesiveness is deteriorated.

[0068] In the present invention, the beta resin content is determined in accordance with ASTM D4312 (Standard Test Method for Toluene-Insoluble(TI)Content of Tar and Pitch) to extract the toluene insoluble matter, and then D2318(Standard Test Method for Quinoline -Insoluble(QI)Content of Tar and Pitch) The content of the quinoline-insoluble matter in the soluble matter is the amount remaining after removing the quinoline-insoluble matter.

[0069] In addition, the coal tar has a fixed carbon content of 10% by weight at 25°C relative to the total weight of the coal tar. In particular, the coal tar may have a fixed carbon content of 20 to 30% by weight. If the amount of fixed carbon does not satisfy the above content, the secondary battery performance, i.e., There may be problems with poor discharge capacity and efficiency. Also, if the amount of fixed carbon is too low, To achieve the coating effect, the rotation speed of the mixer is increased when mixing with artificial graphite. The temperature inside the mixer and the mixture increases as the rotation rate increases. However, if the amount of fixed carbon increases, there is a possibility that the performance will deteriorate. In cases where liquefaction is difficult, the benefits of using liquid coating are not obtained. The disadvantage is that it is not possible to do this and it must be treated in a more advanced process.

[0070] The coal tar has a light oil content of 30% by weight based on the total weight of the coal tar. % or less. Specifically, the coal tar may have a light oil content of the whole coal tar. 5% to 30% by weight, or 10% to 30% by weight, or 10% to 30% by weight, or In the present invention, the light oil content may be from 100% to 200% by weight. It is composed of Talen.

[0071] The viscosity of the coal tar can be between 5000 and 30000 mPa·s at 50°C. If it is lower than the range, the wettability is poor, so the artificial graphite base material and coal tar separate. On the other hand, if the viscosity is higher than the range, the coating quality of the base material may be deteriorated. However, if the viscosity is too high, the impregnation property will be improved, but the adhesive property will be low and phase separation will occur between the artificial graphite matrix. This can cause problems and degrade the quality of the coating.

[0072] In addition, in the method for producing a negative electrode active material for a lithium secondary battery according to the present invention, By controlling the viscosity within the above range, it is possible to obtain an artificial polymer consisting of only single particles, i.e., primary particles. Graphite can be coated immediately. In addition, electrodes can be made without a separate granulation process. It is possible to provide a negative electrode active material with excellent adhesive strength, and it saves energy and costs during the process. reduction effect can be obtained.

[0073] In the step of mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite, Therefore, the coal tar can be charged into the mixing reactor above the artificial graphite. This is to ensure that the coal tar is spread and applied as evenly as possible on the artificial graphite.

[0074] Specifically, coal tar is sprayed from top to bottom into a reactor containing artificial graphite as a base material. It can be added in any of the following ways.

[0075] In the method for producing a negative electrode active material for a secondary battery, The carbonization temperature of the graphite is 1500°C or less. 00 to 1500°C, or 1000 to 1200°C. The heating rate is 5°C / min to 15°C / min, and the carbonization temperature is maintained for 1 to 5 hours. If the carbonization temperature is too low, the volatile matter removal rate will be low, resulting in poor quality of the final product. If the carbonization temperature is too high, unnecessary energy consumption occurs due to the temperature approaching graphitization. There is.

[0076] According to one embodiment, the negative electrode active material for a lithium secondary battery is a material comprising artificial graphite and the artificial graphite surface. The artificial graphite includes a coal tar carbon coating layer formed on the surface thereof, and the artificial graphite is a coal-based coke. The composition of the artificial graphite is the same as that described above. do.

[0077] The artificial graphite may have a sphericity of 0.6 to 1.

[0078] The lithium secondary battery according to one embodiment includes a negative electrode active material manufactured by the above-described manufacturing method. Specifically, a lithium secondary battery comprises a negative electrode comprising a positive electrode and a negative electrode; a positive electrode; and an electrolyte. It may further include a separator disposed therebetween.

[0079] The negative electrode may include a negative electrode active material prepared according to one embodiment, a binder, and an optional conductive material. The materials are mixed to prepare a composition for forming a negative electrode active material layer, which is then applied to a negative electrode current collector. It can be done.

[0080] The negative electrode current collector may be made of copper foil.

[0081] The binder may be polyvinyl alcohol, carboxymethyl cellulose / styrene. ethylene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, Polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinyl fluoride Examples of suitable materials include, but are not limited to, polyethylene, polyethylene, and polypropylene. The binder is contained in an amount of 1% by weight based on the total amount of the composition for forming a negative electrode active material layer. It can be mixed at up to 30% by weight.

[0082] The conductive material is particularly suitable as long as it has conductivity without inducing chemical changes in the battery. Specifically, graphite acetylene graphite such as natural graphite and artificial graphite is used. Black, Ketjenblack, Channel black, Furnace black, Lamp black Carbon black, such as thermal black; conductive fibers, such as metal fibers; fluoride Metal powders such as carbon, aluminum, and nickel powder; zinc oxide, potassium titanate, etc. Which conductive whiskey - conductive metal oxides such as titanium oxide; polyphenylene derivatives A conductive material may be used. The conductive material may be the same as the negative electrode active material layer forming composition. It can be mixed in an amount of 0.1% to 30% by weight based on the total amount of the material.

[0083] Next, the positive electrode is formed by mixing a positive electrode active material, a binder, and optionally a conductive material. After preparing a composition for forming a porous layer, the composition can be applied to a positive electrode current collector. In this case, the binder and conductive material are used in the same manner as in the case of the negative electrode.

[0084] The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, Baked carbon or carbon, nickel, titanium on aluminum or stainless steel surface It is possible to use a material that has been surface-treated with copper, silver, or the like.

[0085] The positive electrode active material is a material capable of reversible intercalation and deintercalation of lithium. Compounds that can undergo intercalation (lithiate intercalation compounds) can be used. do.

[0086] The positive electrode active material is specifically cobalt, manganese, nickel, or a combination thereof. One or more of the composite oxides of the above metals and lithium can be used, and the specific For example, a compound shown in any one of the following chemical formulas can be used.

[0087] Li a A 1-b R b D2 (wherein 0.90≦a≦1.8 and 0≦b≦0. 5);Li a E 1-b R b O 2-c D c (In the above formula, 0.90≦a≦1.8, 0≦b≦0.5, and 0≦c≦0.05); LiE 2-b R b O 4-c D c (The above In the formula, 0≦b≦0.5, 0≦c≦0.05);Li a Ni 1-b-c Co b R c D α (In the above formula, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and and 0<α≦2);Li a Ni 1-b-c Co b R c O 2-α Z α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Cob R c O 2-α Z2 (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05 and 0<α<2);Li a Ni 1-b-c Mn b R c D α (In the above formula, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.0 5 and 0<α≦2);Li a Ni 1-b-c Mn b R c O 2-α Z α (In the above formula and 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2. );Li a Ni 1-b-c Mn b R c O 2-α Z2 (in the above formula, 0.90≦a≦1.8 , 0≦b≦0.5, 0≦c≦0.05 and 0<α<2); Li a Ni b E c G d O2 (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5 and 0.001≦d≦0.1);Li a Ni b Co c Mn d GeO2 (in the above formula , 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d0.5 and 0.0 01≦e≦0.1);Li a NiG b O2 (in the above formula, 0.90≦a≦1. 8 and 0.001≦b≦0.1); Li a CoG b O2 (in the above formula, 0. 90≦a≦1.8 and 0.001≦b≦0.1);Li a MnG b O2 (the above formula where 0.90≦a≦1.8 and 0.001≦b≦0.1);Li a Mn2 G b O4 (wherein 0.90≦a≦1.8 and 0.001≦b≦0.1) );QO2;QS2;LiQS2;V2O5;LiV2O5;LiTO2;LiNiVO4;Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3(0≦f ≦2); and LiFePO4.

[0088] In the above formula, A is Ni, Co, Mn, or a combination thereof; R is , Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof. G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof. Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, J is Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0089] The electrolyte filled in the lithium secondary battery may be a non-aqueous electrolyte or a known solid electrolyte. A biological electrolyte or the like can be used, and one in which a lithium salt is dissolved can be used.

[0090] The lithium salts include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, L Selected from the group consisting of iSbF6, LiAlO4, LiAlCl4, LiCl, and LiI One or more selected species can be used.

[0091] Examples of the solvent for the non-aqueous electrolyte include ethylene carbonate and propylene carbonate. cyclic carbonates such as butylene carbonate and vinylene carbonate, dimethicone Chain carbonates such as diethyl carbonate, methyl ethyl carbonate, and diethyl carbonate acetate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate esters such as γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, Dichloroethane, tetrahydrofuran, 1,2-dioxane, 2-methyltetrahydrofuran ethers such as acetonitrile, nitriles such as acetonitrile, amines such as dimethylformamide However, it is not limited to this. A combination of two or more of these may be used. In particular, a combination of a cyclic carbonate and a chain carbonate may be used. A mixed solvent of these can be preferably used.

[0092] In addition, polymer electrolytes such as polyethylene oxide and polyacrylonitrile are used as electrolytes. Gel polymer electrolytes, in which electrolyte is impregnated into the material, and inorganic solid electrolytes such as LiI and Li3N are used. It is possible.

[0093] The separator is made of an olefin-based polymer such as polypropylene, which is chemically resistant and hydrophobic. Sheets and nonwoven fabrics made from glass fiber, polyethylene, etc. can be used. .

[0094] When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte also serves as a separator. You can also sleep. [Example]

[0095] The following examples of the present invention are provided by those skilled in the art. However, the present invention may be practiced in various different forms. The present invention can be implemented in various ways and is not limited to the embodiments described herein.

[0096] Experimental Example 1: Electrode adhesive strength experiment according to base material composition A negative electrode active material was prepared using artificial graphite having the composition shown in Table 1 below. The stage temperature was 2700°C, and the sphericity of the artificial graphite was 0.7 to 0.8.

[0097] Artificial graphite matrix mixed with coal tar at 15% by weight, Sigma blade type horizontal The mixing was carried out for 45 minutes using a kneader. The inside of the kneader was filled with 60 to 80% of the total area. The raw materials were loaded so that the coal tar used was centrifuged to separate the primary After removing the solids and water (decanted), the quinoline insolubles (Qui The toluene insoluble (QI) content is 2%. The beta resin content is 35%. The fixed carbon content of coal tar was 22%, and the light carbon content was 33%. The oil content was 10%.

[0098] The coated negative electrode active material was then carbonized at 1300°C. The temperature was raised at a rate of 10°C / min. The carbonization temperature was maintained for 3 hours, and then the carbonization was carried out by natural cooling. A negative electrode active material prepared at 50°C was obtained.

[0099] The negative electrode active material prepared above was 97% by weight of carboxymethyl cellulose and styrene butadiene. 2% by weight of binder containing en-rubber and 1% by weight of Super P conductive material in distilled water solvent The mixture was mixed to prepare a negative electrode active material slurry.

[0100] The negative electrode active material slurry was applied to a copper (Cu) current collector and then dried at 100°C for 10 minutes. After that, it was pressed with a roll press. After that, it was dried in a vacuum oven at 100°C for 12 hours. The time when desorption occurred was measured. If no desorption occurred for 12 hours under these conditions, the electrode was deemed usable. The measurement was only conducted for up to 12 hours. This means that the negative electrode active material separates at a certain Cu plate.

[0101] The electrode density of the vacuum-dried negative electrode was 1.5 to 1.7 g / cc.

[0102] [Table 1]

[0103] To explain the results of Table 1, as in the case of Category 1, petroleum coke is mixed with 70% or more of the When the coal-based coke is mixed with the sintered material at a ratio of 30% or less, the sintered material is heated in a vacuum oven for 8 hours. It can be seen that the active material is released after a short time, and the adhesive strength is inferior. It was found that when the material was 100% coal-based coke, the electrode adhesive strength was excellent.

[0104] This is because coal tar is derived from coal and has better adhesion to coal-based coke. So it is thought that this is the case.

[0105] Experimental Example 2 - Electrode adhesive strength experiment according to artificial graphite sphericity and particle size distribution As shown in Table 2 below, the sphericity and particle size distribution are controlled, and the artificial granular material is made from 100% coal-based coke. Graphite was used as the base material. The coal tar used was centrifuged to separate the primary particles. After removing the solids and water (decanted), the quinoline insolubles (Qui The toluene insoluble (QI) content is 2%. The beta resin content is 35%. The fixed carbon content of coal tar was 22%, and that of light oil was 33%. The content of the component was 10%.

[0106] A negative electrode was produced in the same manner as in Example 1, and the electrode detachment time was measured.

[0107] The adhesive strength test of the present invention is carried out by attaching the final manufactured electrode to a 25 cm 2 Cut to size A Tested using STM D4541 test method.

[0108] [Table 2]

[0109] The adhesive strength suitable for use as a negative electrode is 300gf / cm 2 It must be more than In the present invention, sphericity is measured using a FlowCAM PV instrument with ethanol. After dispersing the sample powder in a solvent such as a flow cell, Measurements were made using quantitative image acquisition and shape analysis using a proprietary algorithm.

[0110] Category 6 is a sphericity of 0.6 or less, and as a result, the electrode detachment time is 12 hours, assuming 10 hours. The electrode adhesive strength was 300gf / cm 2 Less than 180gf / cm 2 This is because when the sphericity is less than 0.6, the base material is made of coal tar. This is because it is difficult to perform good matching.

[0111] Category 9 is a material in which the volume fraction of artificial graphite with a particle size of 6 μm to 34 μm is 70% or less. As a result, the electrode detachment time was set at 9 hours, and the electrode detachment occurred before 12 hours, and the electrode adhesive strength was 300 gf / cm 2 Less than 270gf / cm 2 was shown to be inferior.

[0112] Experimental Example 3: Electrode adhesion test according to coal tar content The base material is artificial graphite derived from 100% coal-based coke and has a sphericity of 0.78. The same as in Example 1 was carried out except that the coal tar content was controlled as shown in Table 3 below. The negative electrode active material and negative electrode were manufactured using the same method, and the electrode detachment time was measured. Also included is quinoline insoluble (QI) Toluene insoluble (TI) content, beta-resistance The carbon content, fixed carbon content, and light oil content were the same as in Example 1.

[0113] The adhesive strength test of the present invention is carried out by attaching the final manufactured electrode to a 25 cm 2 Cut to size A Tested using STM D4541 test method.

[0114] [Table 3]

[0115] Category 13 uses a coal tar content of 25% by weight, the electrode detachment time is 8 hours, and the electrode adhesion Force 160gf / cm 2 The characteristics were deteriorated at

[0116] Experimental Example 4: Evaluation of battery performance according to coal tar characteristics Artificial graphite was produced by using coal-based green coke and petroleum-based calcined coke in a ratio of 2:8 as the base material. The negative electrode active material and the negative electrode were prepared using 15% by weight of coal tar having the properties shown in Table 4 below. was manufactured.

[0117] The positive electrode, which is the counter electrode, uses lithium metal (Li-metal), and the electrolyte is ethylene Ethylene Carbonate (EC): Dimethyl Carbonate A mixed solvent with a volume ratio of 1:1 (DMC, Dimethyl Carbonate) A 1 molar LiPF6 solution was used as the solvent.

[0118] Using the above components, a 2032 coin cell type half battery (h We produced a half coin cell.

[0119] [Table 4]

[0120] Currently required characteristics for commercial secondary batteries are a discharge capacity of 350mAh / g or more and an efficiency of 92%. That's all.

[0121] In comparison, categories 15 and 17 did not meet the range for light oil content and fixed carbon content. However, in sections 18 and 19, the quinoline insoluble matter content was high, and the measured discharge capacity and The battery did not meet the requirements of 350mAh / g or more and efficiency of 92% or more.

[0122] The present invention is not limited to the embodiments and may be manufactured in various different forms. A person having ordinary skill in the art to which the present invention pertains can easily understand the technical idea and essential features of the present invention. It should be understood that the present invention may be embodied in other specific forms without modification. Therefore, the above-described embodiments are illustrative in all respects and should not be construed as limiting. It must be understood as something that is not definitive.

Claims

1. Preparing artificial graphite; mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; and carbonizing the artificial graphite on which the coating layer is formed, The artificial graphite has a sphericity of 0.6 to 1. Law.

2. In the step of preparing the artificial graphite, The artificial graphite according to claim 1 contains 20% by weight or more of coal-based coke-derived artificial graphite. Method for producing negative electrode active material for lithium secondary battery.

3. In the step of preparing the artificial graphite, Based on the total volume of artificial graphite, the volume of artificial graphite with a particle size of 6 μm to 34 μm is 70% by volume. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1 .

4. In the step of preparing the artificial graphite, The sphericity of the artificial graphite having a particle size of 5 μm to 10 μm is 0.55 or more.

2. The method for producing the negative electrode active material for a lithium secondary battery according to claim 1.

5. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; Leave, Coal tar is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of artificial graphite. The method for producing the negative electrode active material for a lithium secondary battery according to claim 1 .

6. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; Leave, The coal tar has a quinoline insoluble content (QI) of 1% by weight or more based on the total weight of the coal tar.

2. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1, wherein the content of the metal oxide is up to 7% by weight.

7. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; Leave, The coal tar has a fixed carbon content of 10 to 30% by weight based on the total weight of the coal tar.

2. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1,

8. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; Leave, The coal tar has a light oil content of 30% by weight or less based on the total weight of the coal tar.

2. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1,

9. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; Leave, The coal tar contains 50% by weight of toluene insoluble matter (TI) based on the total weight of the coal tar. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1, wherein:

10. mixing the artificial graphite with coal tar to form a coating layer on the artificial graphite; Leave, The beta resin content of coal tar is 50% by weight or less based on the total weight of coal tar. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1,

11. The step of preparing artificial graphite is as follows: crushing the coke; and graphitizing the coke; The coke is a coal-based coke or a mixture of coal-based coke and petroleum-based coke. can be, The mixture of coal-based coke and petroleum-based coke contains coal-based coke and petroleum-based coke in a ratio of the total weight.

2. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1, wherein the negative electrode active material contains 20% by weight or more of the above.

12. The step of crushing the coke comprises: The lithium secondary battery according to claim 11, comprising a step of adjusting the sphericity of the crushed coke. A method for producing a negative electrode active material for a battery.

13. Artificial graphite and a coal tar-derived carbon coating layer formed on the surface of the artificial graphite, The artificial graphite has a sphericity of 0.6 to 1.

0.

14. The artificial graphite according to claim 13, wherein the artificial graphite contains 20% by weight or more of coal-based coke-derived artificial graphite. The negative electrode active material for lithium secondary batteries is described above.

15. The coal tar-derived carbon coating layer is formed by mixing 1 to 2 parts by weight of the carbon based on 100 parts by weight of the artificial graphite.

14. The negative electrode active material for a lithium secondary battery according to claim 13, wherein the negative electrode active material contains 0 parts by weight of the hydroxybenzoate.

16. In the coal tar-derived carbon coating layer, the coal tar is quinoline-free.

13. The soluble fraction (QI) is 1% to 7% by weight based on the total weight of the coal tar. The negative electrode active material for a lithium secondary battery according to claim 1.

17. In the coal tar-derived carbon coating layer, the coal tar has a fixed carbon content The lithium ion battery according to claim 13, wherein the amount of the lithium ion battery is 10 to 30% by weight based on the total weight of the coal tar. Negative electrode active material for secondary batteries.

18. In the coal tar-derived carbon coating layer, the coal tar contains light oil. The lithium ion sintering agent according to claim 13, wherein the content is 30% by weight or less based on the total weight of the coal tar. Negative electrode active material for secondary batteries.

19. In the coal tar-derived carbon coating layer, the coal tar is toluene-free.

14. The coal tar composition according to claim 13, wherein the soluble fraction (TI) is 50% by weight or less based on the total weight of the coal tar. Negative electrode active material for lithium secondary batteries.

20. In the coal tar-derived carbon coating layer, the coal tar is a beta-resist The coal tar composition according to claim 13, wherein the coal tar contains 50% by weight or less of the total weight of the coal tar. Negative electrode active material for lithium secondary batteries.

21. 13. A method for producing a negative electrode active material for a lithium secondary battery according to any one of items 1 to 12. a negative electrode comprising a negative electrode active material produced from the positive electrode; and A lithium secondary battery, including an electrolyte.

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