KR20150075219A - Method of preparing artificial graphite negative electrode material for rechargeable lithium battery and artificial graphite negative electrode material for rechargeable lithium battery prepared from the same - Google Patents

Abstract

Provided is a method for preparing an artificial graphite negative electrode material for a rechargeable lithium battery, comprising the steps of: mixing chemical coke for manufacturing iron and a metal carbide, and obtaining a mixture; performing a first heat treatment of the mixture and obtaining a carbide; and performing a second heat treatment of the carbide and obtaining a graphitized material. Also, provided is the artificial graphite negative electrode material for the rechargeable lithium battery manufactured from the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial graphite anode material for a lithium secondary battery and an artificial graphite anode material for a lithium secondary battery produced therefrom. 2. Description of the Related Art Artificial graphite anode materials for a lithium secondary battery,

To a process for producing an artificial graphite anode material for a lithium secondary battery and an artificial graphite anode material for a lithium secondary battery produced therefrom.

Recently, a high capacity lithium secondary battery is required due to an increase in the power consumption of the electronic apparatus and the integrated function, and at the same time, the charge / discharge cycle is shortened due to an absolute increase in the use time. Due to the decrease of the charge / discharge cycle, it is required to increase the charge / discharge cycle life of the battery.

At present, natural graphite and artificial graphite have been commercialized and applied mainly to an anode material of a lithium secondary battery. In particular, it is known that natural graphite exhibits higher capacity than artificial graphite. Despite the advantages of such high capacity, natural graphite is known to have inferior lifetime characteristics compared to artificial graphite. In particular, natural graphite is mostly in the form of impression (plate shape). Therefore, natural graphite in the form of spheroidized is mainly used for easiness of electrode manufacturing process, increase of filling density, improvement of output characteristics and the like. It is known that the lifetime characteristics of natural graphite deteriorate during repeated charging and discharging due to defects and internal stress of graphite structure generated through the spheroidization process.

On the other hand, in the case of artificial graphite, the capacity is inferior to that of natural graphite, but the life characteristic is excellent. Accordingly, in recent years, natural graphite and artificial graphite are mixed to be used as an anode material in order to compensate for the disadvantages of the respective materials.

One embodiment of the present invention is to provide a manufacturing method of a high-capacity artificial graphite anode material for a lithium secondary battery, which is simple in manufacturing process and omits manufacturing cost by omitting the purification process and the caulking process in the use of raw materials.

Another embodiment is to provide an artificial graphite anode material for a lithium secondary battery produced from the method for producing artificial graphite anode material for a lithium secondary battery.

One embodiment includes mixing a steel-smelting coke and a metal carbide to obtain a mixture; Subjecting the mixture to a first heat treatment to obtain a carbide; And a second heat treatment of the carbide to obtain graphite. The present invention also provides a method for manufacturing artificial graphite anode material for a lithium secondary battery.

The iron-working smelting coke may contain 1 to 5% by weight of ash.

The average particle diameter (D50) of the iron-soluble coke may be 7 to 100 mu m.

The metal carbide may be a transition metal, an alkali metal, an alkaline earth metal, a 3A group metal, a 3B group metal, a 4A group metal, a 4B group metal, a 5A group, a 5B group, Or a combination of metals.

The average particle diameter (D50) of the metal carbide may be 1 to 100 mu m.

The metal carbide may be mixed in an amount of 1 to 30 parts by weight based on 100 parts by weight of the iron-soluble coke.

The first heat treatment may be performed at a temperature of 800 to 1500 ° C.

The second heat treatment may be performed at a temperature of 2500 to 3000 ° C.

Another embodiment provides an artificial graphite anode material for a lithium secondary battery produced by the method for manufacturing artificial graphite anode material for a lithium secondary battery.

The spacing d002 of the crystal planes of the artificial graphite anode material may be 3.354 to 3.369 angstroms, the lattice constant Lc may be 150 to 1000 angstroms, and the lattice constant La may be 150 to 1000 angstroms.

The details of other embodiments are included in the detailed description below.

It is possible to manufacture artificial graphite anode material for a lithium secondary battery of a high capacity with a simple manufacturing process and a low manufacturing cost by omitting the purification process and the caulking process in the use of raw materials.

1 is a photograph showing the appearance of a massive coke oven mass used in Examples 1 to 4 and Comparative Examples 1 and 2. Fig.
FIGS. 2A and 2B are photographs of a polarizing microscope of the coking coke used in Examples 1 to 4 and Comparative Examples 1 and 2, respectively, at a magnification of 200 times and 500 times.
FIGS. 3A and 3B are scanning electron microscope (SEM) photographs of artificial graphite anode materials for a lithium secondary battery according to Example 1 at magnifications of 5,000 and 10,000, respectively. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Artificial graphite, which is generally used as an anode material for a lithium secondary battery, is mainly produced by a coal-based pitch or a petroleum-based pitch produced through a carbonization process and a graphitization process.

In this case, when the mesophase spherules prepared from the step of producing the optically anisotropic phase of the mesophase pitch produced from the coal-based coal tar or the petroleum-based residual oil generated in the coal carbonization process are used, The development of the layer surface is deteriorated as compared with the natural graphite, so that the discharge capacity is 320 to 340 mAh / g, which is about 80 to 85% of the theoretical discharge capacity. Further, even when artificial graphite is produced using needle-shaped coke having anisotropic structure developed by utilizing the coal-based pitch or petroleum pitch, it is difficult to raise the discharge capacity at the above level by simple heat treatment alone.

The limitation of such a capacity has been developed and applied to a method of adding a small amount of metal, metal oxide, metal hydroxide, etc. containing elements such as B, Ti, Al, Si, Ni and the like having a catalytic graphitizing effect to a graphitization process . However, in the above process, after the catalyst-containing compound is mixed with the raw coke or the calcined coke, the mixture is subjected to a heat treatment process for forming a metal carbide at a low temperature and then subjected to a graphitization process, There is a problem that quality deviation occurs or control of graphitization speed and temperature condition is difficult.

On the other hand, in the manufacturing process of coke, there is a method of producing a pitch-controlled pitch component in an appropriate process using coal-based coal tar and petroleum residue, followed by caulking reaction. These processes include delayed coking, fluid coking, contact coking, flexi coking, and the like. The delayed caulking method is a method in which the heavy oil is heated in advance and reacted for several hours in a caulking drum and then extracted by high-pressure jet water. Industrially, a delayed caulker is used as a reaction device and productivity, uniformity and stability Is relatively superior to other processes and is therefore being applied commercially. However, the above process is complicated due to very complicated process conditions for the carbonization rate and temperature in the caulking process, and thereafter, it is necessary to carry out a separate carbonization process to produce an artificial graphite anode material and then connect it to a graphitization process there is a problem.

In particular, the coke used for the production of artificial graphite anode materials is generally an anisotropic or isotropic coke, which can be controlled through impurities and molecular weight through purification processes for coal-based coal tar and petroleum residues, Is manufactured through a delayed caulking process. Such a process involves separately collecting coal-based coal tar and petroleum residues, then proceeding the process of producing and refining the pitch under very selective conditions, and the process cost is high due to the relatively low productivity in terms of caulking conditions have.

In one embodiment, an artificial graphite anode material can be manufactured using a coke-based coke produced through a metallurgical coke production process in a steelmaking process which is commercially applied. Therefore, since a high-capacity artificial graphite anode material can be produced immediately after the carbonization process or the petroleum-based pitch purification process and the caulking process, the production process is simple and the production cost can be greatly reduced.

The use of coke is essential in the blast furnace method. This is because the coke serves not only as a reducing agent for reducing iron ore in the blast furnace, but also as a heat source necessary for maintaining the temperature, and has a function of maintaining air permeability in the blast furnace to which hot air is supplied by having proper pores. In addition, when high-strength coke is used as a raw material, the blast furnace can be stabilized and the production of pig iron can be increased, and the amount of pulverized coal can be increased, so that the fuel cost can be reduced and the blast furnace productivity can be improved.

In the case of coking coal for the production of metallurgical coke, physical properties for thermal behavior include cohesion, swelling, flow, temperature range, volatile content and the like. The physical properties of the cokes include vitrinite Average reflectance, and strength index. Raw coking is generally formulated with reference to two to three properties, rather than one cement product characterization result. In general, Fe and Al components, which are known as carbon ash components, are uniformly distributed in the coke. Also, since a large amount of tar component is removed through the carbonization process, the carbonization yield is relatively high.

Specifically, the artificial graphite anode material for a lithium secondary battery according to an embodiment is obtained by mixing a steel-fired coke and a metal carbide to obtain a mixture, subjecting the mixture to a first heat treatment to obtain a carbide, And can be produced by obtaining a cargo.

The iron-working smelting coke is produced through a metallurgical coke production process in a steelmaking process as described above, and can be obtained through a coal drying process. Therefore, it is distinguished from the isotropic coke or the needle coke obtained by controlling the impurities, the molecular weight and the degree of structural orientation through the refining process of the coal-based coal tar or the petroleum residual oil generated during the coal drying process and then through the caulking process. Wherein the isotropic coke is a coke having an isotropic texture, and the coke is a coke having an anisotropic texture.

Specifically, the components of the marsh coke, the needle coke and the isotropic coke are shown in Table 1 below.

Ash (wt%) Volatile matter (% by weight) Fixed carbon (wt%) Mars Coke 1 to 5 Less than 0.1 95 or higher Needle coke Less than 0.01 0.5 99 or more Isotropic coke 0.01 to less than 1 0.4 98 or higher

Referring to Table 1, the iron-soluble coke may contain 1 to 5% by weight of ash. On the other hand, the acicular coke contains ash in an amount of less than 0.01% by weight, and the isotropic coke contains ash in an amount of not less than 0.01% by weight and less than 1% by weight. In other words, since the ignitable cokes are not subjected to a separate ash removal process, they contain metallic impurities such as Si, Fe, and Al, whereas the needle-shaped cokes and isotropic cokes contain impurities such as Si The ash components contained in the gas are removed.

The iron-soluble coke used for producing the artificial graphite anode material has an average particle size (D50) of 7 to 100 mu m, specifically, an average particle size (D50) of 7 to 50 mu m through pulverization of coal-based coke, May have an average particle diameter (D50) of 10 to 30 mu m. When a steel-working coke having an average particle diameter (D50) within the above range is used as an anode material, it is possible to realize an appropriate electrode density, and a small amount of a fine powder is generated, and side reactions with an electrolyte are reduced, .

When the metal carbide is mixed with the ignitable cokes, the graphitization reaction of the coke is promoted through the catalytic graphitization process, so that the crystallinity of the graphite formed by the heat treatment is increased, thereby securing a high-capacity artificial graphite anode material.

The catalytic graphitization reaction is a reaction in which graphite is formed through a dissolution regeneration reaction of a metal carbide to a coke. The catalytic graphitization reaction has an effect of increasing the degree of graphitization at the same temperature, and has the effect of reducing the graphitization temperature at the same degree of graphitization.

The metal carbide may be any metal carbide forming carbide. For example, the metal carbide may be a transition metal, an alkali metal, an alkaline earth metal, a 3A group metal, a 3B group metal, a 4A group metal, a 4B group metal, a 5A group element, a 5B group element, A group element, or a combination thereof, and may be a compound bonded to the metal with carbon. For example, the transition metal may include Mn, Ni, Fe, Cr, Co, Cu, Mo, W, Te, Re, Ru, Os, Rh, Ir, Pd, Pt, The metal may be Li, Na, K or a combination thereof. Examples of the alkaline earth metals include Be, Sr, Ba, Ca, Mg, or combinations thereof. The Group 3A metal may be selected from the group consisting of B, Al, Ga, and combinations thereof. The Group 4A metal may be at least one selected from the group consisting of Ti, Zr, Hf, or a combination thereof. The 4B group metal may be Si, Ge, Sn or a combination thereof. The Group 5A element may be V, Nb, Ta or a combination thereof. , And the Group 5B element may be P, Sb, Bi or a combination thereof. The lanthanum series elements include Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, U, Nb, Pu, or a combination thereof.

The average particle diameter (D50) of the metal carbide may be 1 to 100 mu m, specifically 1 to 50 mu m, and more specifically 1 to 10 mu m. When the average particle diameter of the metal carbide is within the above range, the contact area with the coke is large, so that the reaction promoting the graphitization is actively performed, thereby enabling efficient graphitization in the catalytic graphitization process and maintaining a reasonable process cost.

The metal carbide may be mixed in an amount of 1 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the iron-soluble coke. When the metal carbide is mixed within the above content range, a high-capacity artificial graphite anode material can be obtained as the degree of graphitization increases.

As a pretreatment step, a carbonization process may be performed in which the crushed iron-soluble coke and the metal carbide are mixed to obtain a mixture, followed by carbonizing the mixture by a first heat treatment.

The first heat treatment may be performed at a temperature of 800 to 1500 ° C, and more specifically, at a temperature of 1000 to 1300 ° C. When the heat treatment for carbonization is performed within the temperature range, the amount of the fixed carbon is high and the amount of the sublimation component generated in the graphitization process can be reduced, which is preferable. In addition, when the heat treatment is performed within the above-mentioned temperature range, it is not necessary to include a facility equipped with a high temperature heating element required for heat treatment at a higher temperature.

The first heat treatment may be performed in an atmosphere containing nitrogen, argon, hydrogen, helium or a mixed gas thereof, or under a vacuum.

Next, the graphitization process for graphitizing the carbide obtained by the carbonization process by the second heat treatment may be performed.

The graphitization process may be performed in an induction heating system of Linn HIGH THERM GMBH, Germany, but is not limited thereto. In the induction heating method, it takes 30 minutes to 1 hour to raise the temperature to 3000 ° C.

The second heat treatment may be performed at a temperature of 2500 to 3000 ° C, and more specifically, at a temperature of 2500 to 2800 ° C. When the heat treatment for graphitization is performed within the temperature range, graphitization reaction is actively performed and the generation amount of sublimation components of carbon is small.

The second heat treatment may be performed in an atmosphere containing nitrogen, argon, hydrogen, helium or a mixed gas thereof, or under a vacuum.

The artificial graphite anode material produced by the above-described production method can have a high degree of graphitization by increasing the degree of crystallization of carbon. Specifically, in the XRD analysis, d002 representing the interval of crystal planes may be 3.354 to 3.369 angstroms, specifically, 3.360 to 3.368 angstroms. Also, in the XRD analysis, the lattice constant Lc may be 150 to 1000 angstroms, and more specifically 200 to 300 angstroms. Also, in the XRD analysis, the lattice constant La may be 150 to 1000 angstroms, specifically 500 to 700 angstroms. When the value of d002 has a small value within the range, and when the values of Lc and La each have a large value within the range, high degree of graphitization can be exhibited.

The artificial graphite anode material described above can secure a high capacity, and thus can be usefully used in a lithium secondary battery.

The lithium secondary battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The electrode assembly includes a sealing member that is housed in a battery container, impregnates the electrolyte, and seals the battery container.

The negative electrode may be prepared by preparing a composition for forming a negative electrode active material layer by mixing the above artificial graphite negative electrode material, a binder and optionally a conductive material, and then applying the composition to an anode current collector such as copper.

Examples of the binder include polyvinyl alcohol, carboxymethylcellulose / styrene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene Polypropylene and the like can be used, but the present invention is not limited thereto.

The binder may be mixed in an amount of 1 to 30% by weight based on the total amount of the composition for forming the negative electrode active material layer.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and specifically includes graphite such as natural graphite and artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The conductive material may be mixed in an amount of 0.1 to 30% by weight based on the total amount of the composition for forming the anode active material layer.

The positive electrode may be prepared by mixing a positive electrode active material, a binder and optionally a conductive material to prepare a composition for forming a positive electrode active material layer, and then applying the composition to a positive electrode current collector such as aluminum.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, at least one of complex oxides of lithium and at least one kind selected from cobalt, manganese and nickel can be used.

The electrolyte solution may be a lithium salt and a non-aqueous organic solvent.

The lithium salt is _{LiCl, LiBr, LiI, LiClO 4} , LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, lithium 4-phenylborate, and imide.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, But are not limited to, ricifrcr, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, An ether, a methyl ethyl pyrophonate, an ethyl propionate, a methyl ethyl ketone derivative, a methyl ethyl ketone derivative, a methyl ethyl ketone derivative, Etc. may be used.

The separator may be an olefin-based polymer such as polypropylene, which is chemically resistant and hydrophobic; A sheet or a nonwoven fabric made of glass fiber, polyethylene or the like can be used. When a solid electrolyte such as a polymer is used as the electrolytic solution, the solid electrolytic solution may also serve as a separation membrane.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only the preferred embodiments of the present invention, and the present invention is not limited by the following examples.

(Artificial graphite for lithium secondary batteries Anode material  Produce)

Example  1 to 4

(Ash content: 1 to 5% by weight) for metallurgical iron manufacturing was crushed through a jet mill into powder having an average particle diameter (D50) of 15 탆. The above-mentioned ignitable coke powder and SiC powder having an average particle diameter (D50) of 3 mu m were mixed to obtain a mixed powder. At this time, the SiC powders were mixed in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the coconut coke as shown in Table 2 below. The mixed powder was heat-treated at 1300 ° C for 1 hour in an N ₂ atmosphere to obtain a carbide. The carbide was heat-treated at 2800 캜 for 2 hours in an Ar gas atmosphere in an induction heating furnace of Linn HIGH THERM GMBH (Germany) to graphitize to produce artificial graphite.

Comparative Example  One

(Ash content: 1 to 5% by weight) for metallurgical iron manufacturing was crushed through a jet mill into powder having an average particle diameter (D50) of 15 탆. The ignited coke powder was heat-treated at 1300 ° C for 1 hour in an N ₂ atmosphere to obtain a carbide. The carbide was heat-treated at 2800 캜 for 2 hours in an Ar gas atmosphere in an induction heating furnace of Linn HIGH THERM GMBH (Germany) to graphitize to produce artificial graphite.

Comparative Example  2

Artificial graphite was prepared in the same manner as in Comparative Example 1, except that the graphite was heat-treated at 3000 캜 for 2 hours obtained in Comparative Example 1.

Comparative Example  3

(Ash content: 0.1 wt% or less) obtained through a pitch refining step and a caulking step was crushed through a jet mill into powder having an average particle diameter (D50) of 15 탆. The ignited coke powder was heat-treated at 1300 ° C for 1 hour in an N ₂ atmosphere to obtain a carbide. The carbide was heat treated in an Ar gas atmosphere at 3000 DEG C for 2 hours in an induction heating furnace of Linn HIGH THERM GMBH, Germany to produce artificial graphite.

Coke: weight ratio of SiC Graphitization temperature (캜) Example 1 100: 5 2800 Example 2 100: 10 2800 Example 3 100: 15 2800 Example 4 100: 20 2800 Comparative Example 1 100: 0 2800 Comparative Example 2 100: 0 3000 Comparative Example 3 100: 0 3000

Rating 1: Mars Coke  Photo analysis

1 is a photograph showing the appearance of a massive coke oven mass used in Examples 1 to 4 and Comparative Examples 1 and 2. Fig. FIGS. 2A and 2B are polarization microscope photographs of the coking coke used in Examples 1 to 4 and Comparative Examples 1 and 2, respectively, the magnifications being 200 times and 500 times, respectively.

Referring to FIG. 1, the coke used in Examples 1 to 4 and Comparative Examples 1 and 2 is obtained by grinding coke used in an iron mill furnace.

Referring to FIGS. 2A and 2B, the iron-based smelting coke used for producing the artificial graphite anode material for a lithium secondary battery exhibits optically isotropic properties.

Evaluation 2: Artificial graphite anode material SEM  Photo analysis

FIGS. 3A and 3B are scanning electron microscope (SEM) photographs of artificial graphite anode materials for a lithium secondary battery according to Example 1 at magnifications of 5,000 and 10,000, respectively. FIG.

Referring to FIGS. 3A and 3B, the artificial graphite produced in Example 1 exhibits a comparatively isotropic particle shape and shows a relatively smooth particle surface. The particle shape is close to the shape of spherical shape without holding the angle. This shape can increase the tap density of the powder.

Evaluation 3: Artificial graphite anode material Graphitization degree  analysis

Table 3 shows the results of X-ray diffraction (XRD) analysis for evaluating the degree of graphitization of the artificial graphite anode materials produced in Examples 1 to 4 and Comparative Examples 1 to 3.

XRD analysis was performed under the following conditions.

Slit Condition: Divergence Silt, Scattering Slit 0.5 °, Receiving Slit 0.15mm

X-ray wavelength: 1.541838 Å (Cu Kαm)

Scan conditions: 0.02 step, 1 ° / min.

d002 (A) Lc (A) La (A) La / Lc Example 1 3.368 200 580 2.9 Example 2 3.365 218.3 603.5 2.8 Example 3 3.361 247.0 632.9 2.6 Example 4 3.360 250 638.8 2.6 Comparative Example 1 3.378 160 390 2.4 Comparative Example 2 3.371 187.4 446.9 2.4 Comparative Example 3 3.370 364 610 1.7

In Table 3, d002 represents the interval of crystal planes in XRD analysis, and Lc and La represent lattice constants in XRD analysis.

As shown in Table 3, artificial graphite of Examples 1 to 4 obtained by mixing the metal carbides with the iron-working smelting coke was found to have a small value of d002 and a large value of Lc and La , It can be seen that the degree of graphitization is greatly increased.

Also, in Examples 1 to 4, although the graphitization was proceeded at 2800 ° C, graphitization degree was higher than Comparative Example 2 which was graphitized at 3000 ° C without using metal carbide.

In comparison with Comparative Example 3 in which the graphite was subjected to graphitization at 3000 ° C using an acicular coke, the value of d002 and La in Example 4 exhibited a higher degree of graphitization, while the value of Lc showed a lower value.

Evaluation 4: Capacity and efficiency analysis of lithium secondary battery

Artificial graphite and polyvinylidene fluoride (PVdF) prepared in Examples 1 to 4 and Comparative Examples 1 and 2 as negative electrode active materials were added to a solvent of N-methylpyrrolidone (NMP) at a weight ratio of 95: 5 to prepare a slurry . The slurry was applied to a copper foil, dried, and roll pressed to produce a negative electrode. A coin half cell was fabricated using the negative electrode and a lithium metal as its counter electrode and using a separator made of polyethylene. At this time, the electrolytic solution composition was prepared by dissolving LiPF ₆ in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3: 7.

The cells were charged and discharged under the following conditions, and the results are shown in Table 4 below.

Charging: 0.1C-rate, CC / CV mode, 0.01V / 0.01C cutoff

Discharge: 0.1C-rate, CC mode, 1.5V cut-off

Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Charging / discharging efficiency (%) Example 1 335.4 282.6 84.3 Example 2 363.6 295.9 81.3 Example 3 368.3 304.8 82.8 Example 4 370.8 306.8 82.7 Comparative Example 1 273.3 258.8 94.7 Comparative Example 2 261.8 247.5 94.5 Comparative Example 3 366.5 304.2 83.2

In Table 4, the charge-discharge efficiency (%) is obtained as a percentage of the initial charge capacity versus the initial charge capacity.

It can be seen from Table 4 that in Examples 1 to 4, in which artificial graphite obtained by mixing steel carbide and metal-smelting coke together as an anode material for a lithium secondary battery, a high capacity can be secured.

Also, referring to Examples 1 to 4, it can be seen that the charge-discharge capacity increases as the degree of graphitization increases.

On the other hand, in Examples 1 to 4, the lower charge / discharge efficiency is due to the decrease in capacity due to the side reaction with the electrolyte as the degree of graphitization increases. This is because the surface coating process applied in the conventional anode material industry The charge / discharge efficiency can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And it goes without saying that the invention belongs to the scope of the invention.

Claims (12)

Mixing the iron-based refractory coke and the metal carbide to obtain a mixture;
Subjecting the mixture to a first heat treatment to obtain a carbide; And
A step of subjecting the carbide to a second heat treatment to obtain graphite
Wherein the anode and the cathode are made of the same material.
The method according to claim 1,
The method for producing artificial graphite anode material for a lithium secondary battery according to claim 1, wherein the iron-soluble coke comprises ash in an amount of 1 to 5% by weight.
The method according to claim 1,
Wherein the average grain size (D50) of the iron-working smelting coke is 7 to 100 mu m.
The method according to claim 1,
The metal carbide may be a transition metal, an alkali metal, an alkaline earth metal, a 3A group metal, a 3B group metal, a 4A group metal, a 4B group metal, a 5A group, a 5B group, Wherein the carbonaceous material is a carbide containing a metal in a combination of a metal and a metal.
The method according to claim 1,
Wherein the average particle diameter (D50) of the metal carbide is 1 to 100 mu m.
The method according to claim 1,
Wherein the metal carbide is mixed in an amount of 1 to 30 parts by weight with respect to 100 parts by weight of the iron-working smelting coke.
The method according to claim 1,
Wherein the first heat treatment is performed at a temperature of 800 to 1500 ° C.
The method according to claim 1,
Wherein the second heat treatment is performed at a temperature of 2500 to 3000 占 폚.
The artificial graphite anode material for a lithium secondary battery produced by the method of any one of claims 1 to 8.
10. The method of claim 9,
Wherein an interval d002 of crystal faces of the artificial graphite anode material is 3.354 to 3.369 angstroms.
10. The method of claim 9,
Wherein the artificial graphite anode material has a lattice constant Lc of 150 to 1000 ANGSTROM.
10. The method of claim 9,
Wherein the artificial graphite anode material has a lattice constant La of 150 to 1000 ANGSTROM.

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