KR20020037889A - Method of preparing negative active material for lithium secondary battery, negative active material for lithium secondary battery prepared by same, and lithium secondary battery comprising negative active material - Google Patents

Abstract

PURPOSE: Provided are a process for producing an anode active material for a lithium secondary battery having excellent capacity and efficiency and the lithium secondary battery containing the anode active material. CONSTITUTION: The process for producing the anode active material comprises: adding a resin or a hard carbon to pitch or tar, wherein the resin is selected from the group consisting of a novolac resin, a resol resin, a furan resin, RAN, and a phenol resin; coking the mixture; carbonizing the coked product; performing the graphitization of the carbonized product. And the lithium secondary battery comprises an anode containing the anode active material, a cathode containing a cathode active material represented by the formula: LiMxNyO2, a separator, and an electrolyte. In the formula, M is selected from the group consisting of Co, Ni, and Mn, N is selected from the group consisting of Ni, Mn, Ti, Sr, and Y, x is 0.1 to 1, and y is 1-x.

Description

TECHNICAL OF PREPARING NEGATIVE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, NEGATIVE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY PREPARED BY SAME, AND LITHIUM SECONDARY BATTERY COMPRISING NEGATIVE ACTIVE MATERIAL}

[Industrial use]

The present invention relates to a method for producing a negative electrode active material for a lithium secondary battery, a negative electrode active material for a lithium secondary battery produced by the manufacturing method and a lithium secondary battery comprising the negative electrode active material, and more particularly, a negative electrode for a lithium secondary battery excellent in capacity and efficiency It relates to a method for producing an active material.

[Prior art]

Lithium secondary batteries are prepared by reversibly inserting and detaching lithium ions as a positive electrode and a negative electrode, and filling an organic or polymer electrolyte between the positive electrode and the negative electrode, and lithium ions are inserted / desorbed at the positive electrode and the negative electrode. When produced, electrical energy is generated by oxidation and reduction reactions.

A carbon-based material is used as a negative electrode active material of a lithium secondary battery, and a chalcogenide compound is used as a positive electrode active material, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x O Composite metal oxides such as ₂ (0 <x <1) and LiMnO ₂ have been used.

Carbonaceous materials used as negative electrode active materials in lithium secondary batteries include crystalline carbon and amorphous carbon. Among them, crystalline carbon which is mainly used can be further classified into artificial graphite and natural graphite. Typical artificial graphite is mesophase carbon microbeads (MCMB) prepared by heat-treating pitch and extracting mesophase spheres and mesophase carbon fibers (mesophase) prepared by carbonization after stabilization by spinning in fiber form. carbon fiber (MCF). They have a cylindrical particle shape with a small ratio of spherical or long diameter, and have high charging and discharging efficiency. However, the powder has a high crystallinity even when graphitized at 3000 ° C. due to the microstructure difference of the carbon material. There is a disadvantage that the discharge capacity is small because of the difficulty. In particular, the mesophase carbon microbead powder manufacturing process yields a very low disadvantage. In addition, unlike natural mesophase carbon microbeads or mesophase carbon fiber, natural graphite has a high discharge capacity, low efficiency, and the shape of powder particles is plate-like, so that high-rate characteristics are poor and lifetime characteristics are deteriorated.

The present invention is to solve the above-described problems, an object of the present invention is to provide a method for producing a negative electrode active material for lithium secondary batteries capable of producing a negative electrode active material for lithium secondary batteries with excellent capacity and efficiency.

Another object of the present invention to provide a negative electrode active material for a lithium secondary battery prepared by the above method.

Still another object of the present invention is to provide a lithium secondary battery including the negative electrode active material prepared by the above-described method.

In order to achieve the above object, the present invention is to add a hard carbon or a resin to the pitch (Par) or tar (Tar) that is a carbon raw material, to coke the mixture, to carbonize the coke product, It provides a method for producing a negative electrode active material for a lithium secondary battery comprising a step of graphitizing carbide.

The present invention also provides a negative electrode active material prepared by the above method, a negative electrode comprising the negative electrode active material and a positive electrode comprising a positive electrode active material of the formula (1), a separator located between the positive electrode and the negative electrode; And it provides a lithium secondary battery comprising an electrolyte impregnated in the positive electrode, the negative electrode and the separator.

[Formula 1]

LiM _x N _y O ₂

(In Formula 1, M is selected from the group consisting of Co, Ni and Mn,

N is selected from the group consisting of Ni, Mn, Ti, Sr and Y,

x is 0.1 to 1,

y is 1-x.)

Hereinafter, the present invention will be described in more detail.

In the manufacturing method of the negative electrode active material of this invention, hard carbon or resin is added to pitch or tar which is a carbon raw material first. Hard carbon powders and resins added are refined the pseudo-carbon layer formed during the coking and carbonization heat treatment, and turbostratic on the surface of the carbon powder in the graphitization process. By forming a layer or an onion ring structure to reduce side reactions due to decomposition of the electrolyte solution to increase the charge and discharge efficiency of the active material to be produced and to be able to use the electrolyte of various kinds, in particular polycarbonates.

Preferred hard carbons are carbon black, acetylene black and the like, and resins include novolac resin, resol resin, furan resin and perfuryl alcohol. Furfuryl alcohol, RAN resin (ask: full name) or phenol resin can be used.

The hard carbon preferably has a particle size of 1 μm or less, more preferably 0.5 μm or less. In the case of hard carbon having a size of more than 1 μm, it is difficult to refine the pseudo carbon layer and to form a turbostratic layer or an onion ring structure on the surface of the carbon powder in the graphitization process. it's difficult. As for the addition amount of the said hard carbon, 0.1-10 weight% of the weight of the said carbon raw material is preferable. If the amount of hard carbon is less than 0.1% by weight, the pseudo-carbon layered structure is not refined. If the amount of hard carbon is more than 10% by weight, the discharge capacity and initial efficiency of the finally obtained graphite powder are reduced.

As for the addition amount of the said resins, 0.1-30 weight% of the weight of the said carbon raw material is preferable. If the amount of resin added is less than 0.1% by weight, it is difficult to refine the pseudo carbon layer, and it is difficult to form a turbostratic layer or an onion ring structure on the surface of the carbon powder in the graphitization process. If it is greater than 30 wt%, the voltage flatness of the final obtained graphite powder is deteriorated, and the discharge capacity and initial efficiency are reduced.

The mixture is heat-treated at 200 to 400 ° C. for 2 to 4 hours while stirring in a reactor in a nitrogen atmosphere to remove volatile components and generated gases such as CO ₂ . Subsequently, the product obtained by heat treatment is subjected to coking by heat treatment at 300 to 600 ° C. for 1 to 20 hours. The carbonized material was carbonized at 800 to 1200 ° C. for 2 to 10 hours in a nitrogen atmosphere, and then the obtained carbide was graphitized to a temperature of 2800 to 3000 ° C. for 0.1 to 10 hours in an air blocking atmosphere or an inert atmosphere to obtain lithium. A negative electrode active material for secondary batteries is prepared.

The prepared active material is a substance whose I (110) / I (002), which is the CuKα X-ray integrated diffraction intensity ratio (area ratio of diffraction peaks) of the (110) plane and the (002) plane, is 0.04 or less. Since the carbon material having an I (110) / I (002) value of 0.04 or less is crystalline carbon indicating a high capacity, it can be predicted that the negative active material of the present invention also exhibits a high capacity.

The lithium secondary battery using the negative electrode active material of the present invention may be prepared by using the compound of formula 1 as a positive electrode active material as a positive electrode.

[Formula 1]

LiM _x N _y O ₂

(In Formula 1, M is selected from the group consisting of Co, Ni and Mn,

N is selected from the group consisting of Ni, Mn, Ti, Sr and Y,

x is 0.1 to 1,

y is 1-x.)

As the electrolyte, a non-aqueous liquid electrolyte containing a lithium salt and an organic solvent generally used as an electrolyte of a lithium secondary battery may be used, and a polymer electrolyte may also be used. In the case of using a non-aqueous liquid electrolyte, a separator capable of physically separating the negative electrode and the positive electrode should be used. As the lithium salt and the organic solvent, any one generally used in a lithium secondary battery electrolyte may be used, and representative examples thereof include lithium trifluoromethansulfonimide, lithium triflate, and lithium. Lithium salts such as lithium perclorate, LiPF ₆ or LiBF ₄ may be used, and organic solvents such as ethylene carbonate, dimethyl carbonate and diethyl carbonate may be used.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only one preferred embodiment of the present invention and the present invention is not limited to the following examples.

(Example 1)

5 wt% of novolak resin was added to 95 wt% of coal tar pitch. The mixture was heat-treated at 300 ° C. for 3 hours with stirring in a nitrogen atmosphere reactor to remove volatile components and generated gases such as CO ₂ , and then heat-treated at 600 ° C. to make coke. The prepared coke was carbonized at 1000 ° C. for 2 hours and then graphitized in an inert atmosphere at 2800 ° C. to obtain a negative active material for a lithium secondary battery.

(Example 2)

A negative active material for a lithium secondary battery was prepared in the same manner as in Example 1 except that the amount of novolak resin was changed to 10 wt%.

(Example 3)

A negative active material for a lithium secondary battery was prepared in the same manner as in Example 1 except that the amount of novolak resin was changed to 30 wt%.

(Example 4)

A negative active material for a lithium secondary battery was prepared in the same manner as in Example 1, except that 5 wt% of a resol resin was used instead of the novolak resin.

(Example 5)

A negative active material for a lithium secondary battery was prepared in the same manner as in Example 1, except that 10 wt% of a resol resin was used instead of the novolak resin.

(Example 6)

A negative active material for a lithium secondary battery was prepared in the same manner as in Example 1, except that 3 wt% of carbon black was used instead of the noblock resin.

(Example 7)

A negative active material for a lithium secondary battery was prepared in the same manner as in Example 1, except that 10 wt% of carbon black was used instead of the noblock resin.

(Comparative Example 1)

The coal tar pitch was heat-treated at 300 ° C. for 3 hours with stirring in a nitrogen atmosphere reactor to remove volatile components and generated gases such as CO ₂ , and then heat-treated at 600 ° C. to make coke. The prepared coke was carbonized at 1000 ° C. for 2 hours and then graphitized in an inert atmosphere of 2800 ° C. to 3000 ° C. to prepare a negative active material for a lithium secondary battery.

(Comparative Example 2)

Mesoface carbon microbeads were used as the negative electrode active material.

The negative electrode active material powders prepared by the methods of Examples 1 to 7 and Comparative Examples 1 to 2 were mixed with a polyvinylidene fluoride binder and an N-methylpyrrolidone solvent, respectively, to form a slurry, which was thinly coated on copper foil, and dried. To prepare a negative electrode plate. A 2016 type battery was manufactured using the prepared electrode plate, separator, and lithium metal as counter electrodes. At this time, ethylene carbonate / dimethyl carbonate / propylene carbonate containing 1 mol LiPF ₆ was used as the electrolyte solution.

Discharge capacities, initial charge and discharge efficiency, and I (110) / I (002) of the lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 2 were measured, and the results are shown in Table 1 below.

Discharge Capacity [mAh / g] efficiency[%] I (110) / I (002) Example 1 324 92.0 0.024 Example 2 327 92.1 0.016 Example 3 290 91.4 0.045 Example 4 317 91.0 0.029 Example 5 328 93.6 0.015 Example 6 300 90.1 0.038 Example 7 267 91.4 0.047 Comparative Example 1 294 89.4 0.043 Comparative Example 2 305 92.0 0.041

As shown in Table 1, it can be seen that the negative electrode active materials of Examples 1 to 7 have better discharge capacity or initial efficiency than Comparative Examples 1 to 2. In addition, I (110) / I (002), which is an X-ray diffraction intensity ratio of Cu, also shows a value of 0.040 or less when the negative electrode active materials of Examples 1 to 7 exhibit large discharge capacities, whereas the negative electrode active materials of Comparative Examples 1 to 2 It can be seen that represents a value greater than 0.040.

The manufacturing method of the present invention can produce a negative electrode active material for a lithium secondary battery exhibiting high capacity, high efficiency and improved initial efficiency.

Claims (15)

Resin or hard carbon is added to pitch and tar which are carbon raw materials; Coking the mixture; Carbonizing the coking product; A negative electrode including a negative electrode active material manufactured by a manufacturing method including a step of graphitizing the carbide; A positive electrode including the positive electrode active material of Formula 1; A separator positioned between the positive electrode and the negative electrode; And Electrolyte impregnated in the positive electrode, the negative electrode and the separator Lithium secondary battery comprising a. [Formula 1] LiM _x N _y O ₂ (In Formula 1, M is selected from the group consisting of Co, Ni and Mn, N is selected from the group consisting of Ni, Mn, Ti, Sr and Y, x is 0.1 to 1, y is 1-x.) Resin or hard carbon is added to pitch and tar which are carbon raw materials; Coking the mixture; Carbonizing the coking product; Graphitizing the carbide The negative electrode active material for a lithium secondary battery manufactured by the process. The negative active material of claim 2, wherein the resin is selected from the group consisting of novolak resins, resol resins, furan resins, RANs, and phenol resins. The negative electrode active material of claim 2, wherein the amount of the resin is 0.1 to 30% by weight of the carbon raw material. The negative active material of claim 2, wherein the hard carbons are selected from the group consisting of carbon black or acetylene black, and have particles of 1 μm or less. The negative active material of claim 2, wherein the amount of the hard carbon added is 0.1 to 10 wt% based on the weight of the carbon raw material. Resin or hard carbon is added to pitch and tar which are carbon raw materials; Coking the mixture; Carbonizing the coking product; Graphitizing the carbide The negative electrode active material for lithium secondary batteries whose I (110) / I (002) which is the CuK (alpha) X-ray integrated diffraction intensity ratio of (110) plane and (002) plane is 0.04 or less as a carbon active material obtained by the manufacturing method including a process. Resin or hard carbon is added to pitch and tar which are carbon raw materials; Coking the mixture; Carbonizing the coking product; Graphitizing the carbide The manufacturing method of the negative electrode active material for lithium secondary batteries containing a process. The production method according to claim 8, wherein the resins are selected from the group consisting of novolak resins, resol resins, furan resins, RAN and phenol resins. The production method according to claim 8, wherein the amount of the resin added is 0.1 to 30% by weight of the carbon raw material. The production method according to claim 8, wherein the hard carbons are selected from the group consisting of carbon black or acetylene black, and the size of the hard carbon particles is 1 µm or less. The carbon active material for a lithium secondary battery according to claim 8, wherein the amount of the resin added is 0.1 to 10% by weight of the carbon raw material. The method of claim 8, wherein the coking process is performed for 1 to 20 hours at 300 to 600 ℃. The method of claim 8, wherein the carbonization process is performed at 800 to 1200 ° C. for 2 to 10 hours. The method of claim 8, wherein the graphitization process is performed at 2800 to 3000 ° C. for 0.1 to 10 hours in an air barrier atmosphere or an inert atmosphere.