KR20150075218A - 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

According to the present invention, a method for preparing an artificial graphite negative electrode material for a rechargeable lithium battery comprises the steps of: mixing coal-based raw materials and petroleum-based raw materials, and manufacturing a mixed raw material; coking the mixed raw material through a first heat treatment; carbonizing the mixed raw material through a second heat treatment and obtaining a carbide; and graphitizing the powder through a third heat treatment and obtaining a graphitized material.

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. In recent years, approaches to high capacity artificial graphite have begun, and in the area where natural graphite is dominant, artificial graphite seeks to gain market once again as a weapon to improve high output and lifetime characteristics.

Although the artificial graphite anode material based on petroleum has an initial capacity of 340 mAh / g and a relatively high capacity can be achieved, the output characteristic (defined as the capacity retention rate of 2C discharge for 0.2C discharge) is about 80% Needs to be improved.

On the other hand, artificial graphite anode materials based on coal-based coal tar are comparatively low in the initial capacity of 300 mAh / g, but output characteristics (defined as the capacity retention rate of 2C discharge for 0.2C discharge) are higher than 90% It needs to be.

Accordingly, the present invention provides a method for manufacturing an artificial graphite anode material for a lithium secondary battery, which is capable of simultaneously improving the capacity characteristics of a coal system and the output characteristics of a petroleum system by combining a coal system and a petroleum system in the use of artificial graphite.

Another embodiment of the present invention is to provide an artificial graphite anode material for a lithium secondary battery manufactured from the method for manufacturing artificial graphite anode material for lithium secondary battery.

Another embodiment of the present invention relates to a negative electrode for a lithium secondary battery including the negative electrode material.

Another embodiment of the present invention relates to a lithium secondary battery including the negative electrode, the positive electrode and the electrolyte solution.

According to an embodiment of the present invention, there is provided a method of manufacturing a mixed raw material, comprising the steps of: mixing a raw material and a petroleum raw material to produce a mixed raw material; coking the mixed raw material through a first heat treatment; A step of carbonizing the carbonized material through a second heat treatment to obtain a carbide; and a step of graphitizing the carbide through a third heat treatment to obtain a graphite product. The present invention also provides a method for manufacturing a synthetic graphite anode material for a lithium secondary battery.

The coal-based raw material may be a coal-based pitch having a softening point of 70 ° C to 150 ° C, which contains coal-based coal tar from which quinoline-insoluble (QI) has been removed.

The petroleum-based raw material may be a petroleum pitch having a softening point of 150 ° C to 250 ° C including a vacuum residue (VR) or a fluidized catalytic cracking decant oil (FCC DO) .

The step of preparing the mixed raw material may include mixing the coal-based raw material and the petroleum-based raw material with a solvent.

The solvent may be at least one selected from the group consisting of tetrahydrofuran (THF), acetone, benzene, toluene, pyridine and quinoline

In the step of producing the mixed raw material, the petroleum-based raw material may be contained in an amount ranging from 1% by weight to 50% by weight based on 100% by weight of the total of the coal-based raw material and the petroleum-based raw material.

The petroleum-based raw material may be contained in an amount ranging from 10% by weight to 30% by weight based on 100% by weight of the total of the coal-based raw material and the petroleum-based raw material.

The first heat treatment may be performed at a temperature of 450 to 550 ° C.

The second heat treatment may be performed at a temperature of 1200 to 1400 캜.

The third heat treatment may be performed at a temperature of 2600 to 3000 ° C.

The method may further include a step of pulverizing the carbide between the step of obtaining the carbide and the step of obtaining the graphite to obtain a powder.

The powder may have an average particle size in the range of 1 to 20 [mu] m.

According to another embodiment of the present invention, there is provided an artificial graphite anode material for a lithium secondary battery produced by the above-described method.

The artificial graphite anode material for a lithium secondary battery may have a plane spacing d002 measured by X-ray diffraction (XRD) ranging from 0.335 nm to 0.336 nm

According to another embodiment of the present invention, there is provided a negative electrode for a lithium secondary battery including the negative electrode material.

According to another embodiment of the present invention, there is provided a lithium secondary battery including the above-described cathode for a lithium secondary battery, a cathode, and an electrolyte.

There is provided an anode material for a lithium secondary battery capable of improving low-capacity characteristics while maintaining a high output characteristic of a coal-based pitch-based artificial graphite anode material by mixing petroleum pitch with a coal pitch and inducing a chemical interaction therebetween .

FIG. 1 is a flowchart illustrating a method of manufacturing a synthetic graphite anode material for a lithium secondary battery according to an embodiment of the present invention. Referring to 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.

Hereinafter, a method of manufacturing the artificial graphite anode material for a lithium secondary battery according to the present invention will be described with reference to the drawings. 1 is a flowchart for explaining a method of manufacturing an isotropic graphite molded body according to an embodiment of the present invention.

A method for manufacturing artificial graphite anode material for a lithium secondary battery according to an embodiment includes a step (S100) of mixing a coal-based raw material and a petroleum-based raw material to produce a mixed raw material, a step (S102) of coking the mixed raw material through a first heat treatment, (S104) of carbonizing the mixed raw material through a second heat treatment to obtain a carbide (S104); and graphitizing the powder through a third heat treatment to obtain graphite (S108).

Artificial graphite includes coal tar and petroleum residues (FCC DO, VR, etc.).

It is generally known that artificial graphite made from petroleum residues as a raw material is more suitable for high capacity because graphitization becomes easier. It is difficult to manufacture graphite having a domain larger than that of a petroleum based artificial graphite produced from coal-based coal tar Rather, it is known to exhibit characteristics consistent with high power.

The method for producing artificial graphite anode material for a lithium secondary battery according to the present invention can induce a chemical interaction between a carbon-based material and a petroleum-based material by composing a carbon-based material and a petroleum-based material. Accordingly, the production method of the present invention can simultaneously improve the capacity characteristics of the coal system and the output characteristics of the petroleum system.

As a raw material that can be used to induce the chemical interaction at this time, coal-based coal tar and most of the petroleum residue (FCC DO, VR, etc.) can be used. However, when coal-based coal tar and petroleum residue are used as they are, Can be excessively large.

Therefore, it is preferable that the step (S100) of preparing the mixed raw material includes a step of pretreating the coal-based raw material and the petroleum raw material before mixing them.

Specifically, quenoline-insoluble (QI) in the coal-based coal tar is completely removed or controlled to a certain level or the coal-based raw material is used as the coal-based raw material, or the quenoline- Can be used.

As the petroleum-based raw material, quinoline-insoluble (QI) may be completely removed from the petroleum residue or controlled to a certain level or less, or a product prepared at a pitch of 150 ° C to 250 ° C may be used have. If the coal pitch or the petroleum pitch outside the above range is used to induce the formation of the hard pitch, the chemical interaction may be insufficient and the mixing effect of the powder after coking or carbonization becomes insufficient .

More preferably, the coal-based raw material has a softening point of 100 ° C to 150 ° C, and the petroleum-based raw material preferably has a softening point of 180 ° C to 220 ° C.

In the step (S100) of producing the mixed raw material, the following steps may be carried out after dry mixing of the coal-based raw material and the petroleum raw material which have been subjected to the pretreatment step as described above. However, in order to achieve a more uniform composition, it is preferable to undergo a liquid-phase dissolution process through a solvent.

For example, the solvent may be at least one selected from the group consisting of tetrahydrofuran (THF), acetone, benzene, toluene, pyridine, and quinoline, but is not limited thereto. Of these, THF is most preferably used.

When the liquid phase dissolution is completed, the used solvent is distilled.

Meanwhile, it is preferable that the petroleum-based raw material is contained in an amount ranging from 1% by weight to 50% by weight based on 100% by weight of the total of the coal-based raw material and the petroleum-based raw material in the step (S100) of producing the raw material mixture. In the above range, the petroleum-based raw material is more preferably contained in an amount ranging from 10% by weight to 30% by weight based on 100% by weight of the total of the coal-based raw material and the petroleum-based raw material. When the capacitance is within the above range, the capacitance characteristic and the output characteristic can be secured at the same time.

After the step of producing the mixed raw material is completed, the mixed raw material is coked through a first heat treatment (S102). The first heat treatment may be performed at a temperature of 450 to 550 ° C. The first heat treatment is preferably performed at a temperature of about 500 ° C. in the above range.

After the coking step is completed, the mixed raw material is carbonized through a second heat treatment to obtain a carbide (S104). The second heat treatment may be performed at a temperature of 1200 to 1400 캜. The second heat treatment may be performed at a temperature of 1200 to 1400 ° C in the above range, and is preferably a temperature range of about 1300 ° C or less. When carbonized in the above range, an appropriate level of carbonization can be ensured.

After the carbonization step is completed, the carbide may be pulverized to obtain a powder (S106). At this time, the powder may be pulverized to an average particle size (D50 basis) in the range of 1 to 20 mu m, but this is not limitative. The pulverization may be performed using a jet mill or a pin mill.

After the pulverization step is completed, the powdered carbide is then graphitized through a third heat treatment to obtain graphite (S108). The third heat treatment may be performed at a temperature of 2600 to 3000 ° C. Even within this range, it is preferable to perform at a temperature of about 2800 ° C or more. In this case, sufficient crystallization can be ensured. The graphitization may be performed by various methods such as the Acheson method and the induction heating method.

According to another embodiment of the present invention, there is provided an artificial graphite anode material for a lithium secondary battery produced according to the above-described manufacturing method. The artificial graphite anode material for lithium secondary batteries may have a surface interval (d ₀₀₂ ) according to X-ray diffraction analysis (XRD) of 0.335 nm to 0.336 nm.

Another embodiment of the present invention provides a negative electrode for a lithium secondary battery including the negative active material, and another embodiment provides a lithium secondary battery including the negative electrode.

The lithium secondary battery may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of the separator and electrolyte used. The lithium secondary battery may be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

A lithium secondary battery according to an embodiment 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 a negative electrode active material composed of the 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 anode current collector may have a thickness of 3 to 500 mu m. Examples of the negative electrode current collector may include stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface treated with carbon, nickel, titanium, silver or the like on the surface of aluminum or stainless steel. The negative electrode current collector may have fine irregularities on its surface to increase the adhesive force of the negative electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The positive electrode may be prepared by mixing the positive electrode active material, the 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, a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte.

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.

Examples of the organic solid electrolytic solution include a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene and an ionic dissociation group And the like can be used.

As the inorganic solid electrolytic solution, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ⁴ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ - Nitrides, halides and sulfates of Li such as LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the electrolyte solution is preferably used in the form of a solution containing at least one member selected from the group consisting of pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric triamide, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, and the like can be added. Further, a halogen-containing solvent such as carbon tetrachloride, ethylene trifluoride or the like may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. As such a separator, an insulating thin film having high ion permeability and mechanical strength can be used. The pore diameter of the separator may be 0.01 to 10 mu m and the thickness may be 5 to 300 mu m.

The separator specifically includes an olefin-based polymer such as polypropylene having chemical resistance and hydrophobicity; 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 embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

Manufacture of Artificial Graphite Anode Material

Example  One

A mixed pitch solution was prepared by mixing a coal-based pitch (coal tar) near a softening point of 100 ° C and a petroleum pitch (petroleum residue) near a softening point of 200 ° C in THF in a reactor. The weight ratio between the coal-based pitch and the petroleum-based pitch was set to coal-based pitch: petroleum-based pitch = 10:90.

When the dissolution was completed, the solvent was evaporated from the mixed pitch solution to prepare a mixed pitch.

Subsequently, the mixed pitch was coked at about 500 캜 and then carbonized at about 1200 캜. Subsequently, the carbide obtained through the above-described carbonization step was pulverized to have an average particle diameter of 15 mu m using a jet mill or the like. Thereafter, the powder obtained through the pulverization step was crystallized through a heat treatment at about 2800 ° C to produce an artificial graphite anode material.

Example  2

An artificial graphite anode material was produced in the same manner as in Example 1 except that the coal-based pitch and the petroleum-based pitch weight ratio were changed to coal-based pitch: petroleum pitch = 50:50.

Example  3

An artificial graphite anode material was produced in the same manner as in Example 1 except that the coal-based pitch and the petroleum-based pitch weight ratio were changed to coal-based pitch: petroleum pitch = 70: 30.

Comparative Example  One

An artificial graphite anode material was produced in the same manner as in Example 1 except that only the petroleum pitch was used without using coal pitch.

Comparative Example  2

An artificial graphite anode material was produced in the same manner as in Example 1, except that only the coal pitch was used without using the petroleum pitch.

evaluation: XRD  Analysis, discharge capacity and output characteristics evaluation

The artificial graphite anode materials according to Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to XRD analysis to evaluate the change in surface spacing and electrochemical behavior.

The results are shown in Table 1 below.

Raw material (% by weight) XRD plane spacing
(d ₀₀₂ ) (nm) Discharge capacity
(mAh / g) Print
(%@2C/0.2C) coal tar Petroleum residue Comparative Example 1 0 100 0.3357 341 80 Example 1 10 90 0.3358 335 81 Example 2 50 50 0.3359 322 84 Example 3 70 30 0.3359 311 88 Comparative Example 2 100 0 0.3361 300 90

Referring to Table 1, the surface interval tends to decrease from 0.3359 nm to 0.3358 nm as the petroleum residue pitch is added to the coal pitch, and graphitization is more accelerated as the petroleum pitch is contained. On the other hand, in the electrochemical evaluation, the discharge capacity tends to increase as the content of the petroleum pitch increases, and the output characteristic tends to decrease.

The results of the case where only the petroleum pitch was used and the case where only the coal pitch was used according to the comparative example 2 were examined. The case where only the petroleum system was used showed a smaller surface spacing, which is advantageous for graphitization, Of the total population. On the other hand, when the coal system is used alone, the output characteristics are somewhat advantageous.

It can be seen that Examples 1 to 3 can produce artificial graphite with optimized capacity and output characteristics by mixing artificial graphite with coal-based pitch and petroleum pitch.

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 (16)

A step of mixing the coal-based raw material and the petroleum-based raw material to produce a mixed raw material,
Coking the mixed raw material through a first heat treatment,
Carbonizing the mixed raw material through a second heat treatment to obtain a carbide, and
And graphitizing the carbide through a third heat treatment to obtain graphite
Containing
Method for manufacturing artificial graphite anode material for lithium secondary battery. The method of claim 1,
Wherein the coal-based raw material is a coal-based pitch having a softening point of 70 ° C to 150 ° C, which contains coal-based coal tar from which quinoline-insoluble (QI) is removed. The method of claim 1,
The petroleum-based raw material is a petroleum pitch having a softening point of 150 ° C to 250 ° C including a vacuum residue (VR) or fluidized catalytic cracking decant oil (FCC DO) (Method for manufacturing artificial graphite anode material for battery). The method of claim 1,
Wherein the step of preparing the mixed raw material comprises mixing the coal-based raw material and the petroleum-based raw material with a solvent. 5. The method of claim 4,
Wherein the solvent is at least one selected from the group consisting of tetrahydrofuran (THF), acetone, benzene, toluene, pyridine, and quinoline. The method of claim 1,
Wherein the petroleum-based raw material is contained in an amount ranging from 1% by weight to 50% by weight based on 100% by weight of the total of the coal-based raw material and the petroleum-based raw material in the step of producing the mixed raw material. Gt; The method of claim 6,
Wherein the petroleum-based raw material is contained in an amount ranging from 10% by weight to 30% by weight based on 100% by weight of the total of the coal-based raw material and the petroleum-based raw material. The method of claim 1,
Wherein the first heat treatment is performed at a temperature of 450 to 550 ° C. The method of claim 1,
Wherein the second heat treatment is performed at a temperature of 1200 to 1400 占 폚. The method of claim 1,
Wherein the third heat treatment is performed at a temperature of 2600-3000 캜. The method of claim 1,
Further comprising the step of grinding the carbide between the step of obtaining the carbide and the step of obtaining the graphite to obtain a powder. 12. The method of claim 11,
Wherein the powder has an average particle size in the range of 1 to 20 占 퐉. 12. An artificial graphite anode material for a lithium secondary battery produced by the method of any one of claims 1 to 12. The method of claim 13,
Wherein the artificial graphite anode material for lithium secondary batteries has a surface spacing (d002) measured by X-ray diffraction (XRD) in the range of 0.335 nm to 0.336 nm. An anode for a lithium secondary battery comprising the anode material according to any one of claims 1 to 14. An anode of claim 15;
anode; And
Electrolyte
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