KR20090010670A - Method of preparing negative active material for rechargeable lithium battery and rechargeable lithium battery including negative active material prepared therefrom - Google Patents

Abstract

A secondary lithium battery containing negative active material prepared by a method of preparing a negative active material is provided to improve the capability. A method of preparing a negative active material for a lithium secondary battery comprises (S1) a step of forming the complex compound solution by mixing lithium salt, vanadate, amine-based compound and optionally M-containing salt in a solvent; (S2) a step of forming a negative active material precursor by volatilizing the solvent of the complex compound solution; and (S3) a step of manufacturing a negative active material by calcining the negative active material precursor in reduction.

Description

TECHNICAL FIELD OF PREPARING NEGATIVE ACTIVE MATERIAL FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING NEGATIVE ACTIVE MATERIAL PREPARED THEREFROM

The present invention relates to a method for producing a negative electrode active material for a lithium secondary battery, and a lithium secondary battery including a negative electrode active material prepared according to the method, and more particularly, to a method for producing a negative electrode active material for lithium secondary batteries having excellent capacity characteristics and lifetime characteristics. It relates to a lithium secondary battery comprising a negative electrode active material prepared according to the method.

Lithium secondary batteries, which are in the spotlight as power sources of recent portable small electronic devices, exhibit high energy density by showing a discharge voltage that is twice as high as a battery using an aqueous alkali solution using an organic electrolyte.

Examples of the positive electrode active material of a lithium secondary battery include lithium and a transition metal having a structure capable of intercalating lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNi _{1- x} Co _x O ₂ (0 <x <1). Oxides were mainly used.

As the negative electrode active material, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of inserting and desorbing lithium have been applied. The graphite in the carbon series has a low discharge voltage of -0.2V compared to lithium, and the battery using graphite as a negative electrode active material exhibits a high discharge voltage of 3.6V, providing an advantage in terms of energy density of the lithium battery and providing excellent reversibility. It is the most widely used to ensure the long life of the lithium secondary battery. However, the graphite active material has a low capacity in terms of energy density per unit volume of the electrode plate due to the low graphite density (theoretical density of 2.2 g / cc) when manufacturing the electrode plate, and at high discharge voltage, side reactions with the organic electrolyte used are likely to occur. There is a risk of fire or explosion due to battery malfunction or overcharging.

In order to solve this problem, oxide cathodes have recently been developed. The amorphous tin oxide researched and developed by FUJIFILM exhibits a high capacity of 800 mAh / g per weight, but has a fatal problem with an initial irreversible capacity of about 50%, and has a discharge potential of 0.5 V or more and an amorphous characteristic unique overall soft voltage profile. (smooth voltage profile) has a problem that is difficult to be implemented as a battery. In addition, incidental problems such as reduction of some tin oxides from oxides to tin metals due to charging and discharging are also seriously occurring, making it more difficult to use them in batteries.

In addition, Japanese Patent Laid-Open No. 2002-216753 describes Li _a Mg _b VO _c (0.05 ≦ a ≦ 3, 0.12 ≦ _b ≦ 2, 2 ≦ 2c-a-2b ≦ 5) as an oxide cathode. Further, in the Japanese Battery discussion yojijip number 3B05 2002 years been published for a lithium secondary battery negative electrode characteristics of the _{Li 1 .1 V 0 .9 O 2} .

However, the oxide negative electrode does not yet exhibit satisfactory battery performance, and research on it is ongoing.

The present invention provides a method for producing a negative electrode active material for a lithium secondary battery having excellent capacity characteristics and lifespan characteristics.

The present invention provides a lithium secondary battery comprising the negative electrode active material produced by the above-described method.

In order to achieve the above object, the present invention is to form a complex solution by mixing a lithium salt, vanadium salt, optionally M-containing salt, and an amine compound in a solvent, volatilize the solvent of the complex solution to form a negative electrode active material precursor Forming, and reducing and calcining the negative electrode active material precursor to prepare a negative electrode active material for a lithium secondary battery of the formula (1).

[Formula 1]

Li _{1 + x} V _{1 -x- y} M _y O _{2 + z}

(In the formula 1, 0.01 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.3, -0.2 ≤ z ≤ 0.2, M is composed of transition metals other than vanadium, alkali metals, alkaline earth metals, semimetals, and combinations thereof Element selected from the group.)

The present invention also provides a lithium secondary battery comprising a negative electrode comprising a negative electrode active material prepared according to the method, a positive electrode including a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions, and an electrolyte to provide.

The negative electrode active material for a lithium secondary battery according to the method for preparing a negative electrode active material for a lithium secondary battery of the present invention exhibits improved capacity characteristics and life characteristics.

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

The lithium vanadium oxide (hereinafter referred to as LVO) negative electrode active material is manufactured through a process of grinding and mixing Li ₂ CO ₃ or LiOH with V ₂ O ₃ or V ₂ O ₄ , calcining and screening. In general, electrochemical properties such as lifetime characteristics and capacity characteristics of the negative electrode active material are proportional to the electrode density. Therefore, in order to improve the electrochemical properties of LVO, homogeneous mixing of lithium and vanadium, crystal structure, crystallinity, and quantitative ratio of lithium / vanadium control of variables related to electrode density, such as c / a lattice constant ratio, oxidation rate of vanadium, shape and size of primary particles, and particle size of secondary particles, is required.

However, although the crystal structure, crystallinity, lattice constant ratio, and vanadium oxide number can be controlled by the method, the problem of aggregation of particles at high calcination temperatures and the consequent ratio of lithium / vanadium, shape of primary particles, It is difficult to control the size, or the particle size of the secondary particles, it is difficult to secure capacitive electrochemical properties and reproducibility by improving the electrode density.

In particular, LiVMO, which improves the conductivity of the existing LVO, is mainly obtained by pulverizing and mixing Li ₂ CO ₃ or LiOH, a lithium raw material, and V ₂ O ₃ or V ₂ O ₄ , a vanadium raw material, and calcining the mixture. _It is more difficult to control the parameters related to the electrode density because it is prepared by a complex process of grinding and mixing the _secondary oxide secondly, calcining and then screening.

On the other hand, according to the manufacturing method of the negative electrode active material for lithium secondary batteries of this invention, the mixing degree of vanadium and lithium increases, the quantitative ratio of lithium / vanadium, the shape and size of a primary particle, the particle size of a secondary particle, lithium The degree of volatilization, the degree of oxidation of vanadium can be controlled, and the crystallinity can be manufactured to produce a negative electrode active material for a lithium secondary battery that can exhibit improved capacity characteristics, life characteristics, and reproducibility.

The present invention relates to a method for producing a negative electrode active material for a lithium secondary battery, Figure 1 is a flow chart showing a method for producing the negative electrode active material.

Referring to FIG. 1, in the method of preparing a negative active material for a lithium secondary battery of the present invention represented by the following Chemical Formula 1, a lithium salt, a vanadium salt, an M-containing salt, and an amine compound are mixed in a solvent to form a complex solution. (S1), volatilizing the solvent of the complex solution to form a negative electrode active material precursor (S2), and reducing and calcining the negative electrode active material precursor to prepare a negative electrode active material for a lithium secondary battery of Formula 1 below (S3). ).

[Formula 1]

Li _{1 + x} V _{1 -x- y} M _y O _{2 + z}

(In the formula 1, 0.01 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.3, -0.2 ≤ z ≤ 0.2, M is composed of transition metals other than vanadium, alkali metals, alkaline earth metals, semimetals, and combinations thereof Element selected from the group.)

First, a lithium salt, vanadium salt, optionally M containing salt, and an amine compound are mixed in a solvent to form a complex solution (S1).

Examples of the lithium salt include LiX (X is F, Cl, Br, or I), Li ₂ CO ₃ , LiNO ₃ , Li ₂ SO ₄ , LiOH, Li ₂ C ₂ O ₄ , LiCOOH, LiC ₂ O ₂ H ₃ , And hydrates thereof, and those selected from the group consisting of a combination thereof may be used, but is not limited thereto.

The vanadium salt is VOCl ₂ , V0Cl ₃ , V0SO ₄ , VCl ₃ , VCl ₄ , and hydrates thereof, and combinations thereof may be used.

In addition, depending on the desired product, M-containing salts may optionally be further added. M of the M-containing salt may be an element having an ionic radius (0.78 kV) similar to vanadium (III, IV), an octahedral composite structure, or an element having an electronic structure similar to vanadium (III, IV). Representative examples of M include transition metals other than vanadium, alkali metals, alkaline earth metals, and semimetals (having intermediate properties of nonmetals and metals, and typically, bismuth (Bi), antimony (Sb), arsenic (As), and silicon). (Si), germanium (Ge) and the like), and an element selected from the group consisting of a combination thereof. The M is substituted with a homogeneous distribution in the lithium vanadium oxide to improve the structural stability and conductivity of the active material. The M-containing salts include those selected from the group consisting of M-containing hydroxides, hydrates, oxides, nitrides, nitrates, carbonates, sulfates, chlorides, and combinations thereof.

The amine compound chelates lithium ions, vanadium ions, and optionally added M ions to form a complex compound.

As the amine compound, those selected from the group consisting of alkylenediamine tetraacetic acid, tetraalkylalkylenediamine, and combinations thereof can be used. In this case, in the amine compound, alkylene is preferably C ₂ to C ₈ alkylene, and the alkyl is preferably C ₁ to C ₆ alkyl. Representative examples of the amine compound include ethylenediaminetetraacetic acid, tetramethylpropylenediamine, tetramethylethylenediamine, and combinations thereof, and most preferably ethylenediaminetetraacetic acid can be used.

The lithium salt, vanadium salt, and optionally M-containing salt may be appropriately mixed in the molar ratio between the elements of the formula (1), preferably used in the following molar ratio.

The lithium salt and the vanadium salt are preferably added so that the molar ratio of lithium and vanadium is 1.01: 1 to 1.5: 1, and more preferably 1.05: 1 to 1.2: 1. Within this range, there is an advantage in that a mono-phase is formed, and if it is out of the range, an additional phase may be formed, which is not preferable.

The vanadium salt and the M-containing salt are preferably added so that the molar ratio of vanadium and M is 1.0: 0 to 0.7: 0.3, more preferably 0.99: 0.01 to 0.8: 0.2. Within this range, there is an advantage in that a single phase is formed, and if it is out of the above range, an additional phase may be formed, which is not preferable.

In addition, the amine compound is preferably added so that the molar ratio of the lithium salt and the amine compound is 1: 1 to 1: 6, and more preferably added so as to be 1: 2 to 1: 4. It is preferable to obtain a uniform lithium oxide within the above range.

Figure 2 is a schematic diagram showing the structure of the complex compound to be produced as an intermediate material during the preparation of the negative electrode active material according to an embodiment of the present invention, since it is expressed theoretically, the complex is not necessarily limited to the following structure. Referring to FIG. 2, the amine compound (2) chelates lithium ions (3), vanadium ions (4), and M ions (5) to form an atomic level homogeneous complex (1). can confirm.

The solvent may be selected from the group consisting of water, alcohols, and combinations thereof, and the alcohols may include ethanol, methanol, isopropanol, and combinations thereof, but is not limited thereto. Most preferably, water may be used as the solvent.

In the case where a polar solvent such as water or alcohol is used as the solvent, an appropriate amount of a basic substance can be added to increase the solubility of the amine compound, which is preferable. As a preferable basic substance, what is represented by following formula (2) can be used.

[Formula 2]

R _n H _{4 - n} NOH

(In Formula 2,

R is alkyl, preferably C ₁ to C ₃ alkyl, more preferably C ₁ to C ₂ alkyl,

N is 0 ≦ n ≦ 4, and more preferably 1 ≦ n ≦ 2.)

Subsequently, the solvent of the complex solution is volatilized to form a gel negative electrode active material precursor (S2).

In order to volatilize the solvent contained in the complex, a drying step is performed at 70 ° C to 400 ° C. The drying step may be performed at 120 ° C, 170 ° C, 220 ° C, 270 ° C, 320 ° C, or 370 ° C. However, when the drying temperature is lower than 70 ℃ may not be a problem that does not dry, it is not preferable, if the drying temperature is higher than 400 ℃ may cause a problem that the drying is uneven, which is not preferable.

Next, the negative electrode active material precursor is reduced and calcined to prepare a negative electrode active material for a lithium secondary battery of Formula 1 below (S3).

The reduction calcination process is preferably carried out at 1500 ° C or less for 0.5 to 24 hours, more preferably at 400 ° C to 1300 ° C for 0.5 to 12 hours. The reduction calcination step may be carried out at 520 ° C, 630 ° C, 730 ° C, 820 ° C, 910 ° C, 1010 ° C, 1120 ° C, 1210 ° C or 1420 ° C. In the above temperature range, the volatilization degree of lithium and the degree of oxidation of vanadium can be controlled to obtain a negative active material having a high crystallinity and an atomized size. However, when it exceeds 1500 degreeC, there exists a problem that a particle aggregates together and a particle coarsens. In addition, it is preferable to obtain a particle having a suitable size in the range of time, and if it is out of the range of time, it may not be preferable because it may not be fired or the size of the particle may be too large.

In addition, the reduction calcination process may be carried out by first heat treatment at 400 ℃ to 700 ℃ for 0.5 to 12 hours, and second heat treatment at 700 ℃ to 1300 ℃ for 0.5 to 12 hours. In the range of the temperature and time it is possible to obtain a negative active material having a high degree of crystallinity and atomized size. In this way, when the reduction calcination step is carried out in the primary and secondary, it is preferable because the composition of lithium and vanadium can be easily adjusted.

In addition, the reducing calcination step may be carried out in a reducing atmosphere such as nitrogen, oxygen, or a mixed gas thereof.

After the reduction calcination process, a negative electrode active material of Formula 1 may be prepared.

[Formula 1]

Li _{1 + x} V _{1 -x- y} M _y O _{2 + z}

(In Formula 1, 0.01 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.3, -0.2 ≤ z ≤ 0.2, M is composed of transition metals other than vanadium, alkali metals, alkaline earth metals, semimetals, and combinations thereof Element selected from the group.)

The negative electrode active material preferably has an average particle diameter of 30 µm or less, more preferably 0.5 µm to 30 µm, and most preferably 0.5 µm to 20 µm. When the average particle diameter of the negative electrode active material exceeds 30 μm, there is a disadvantage that the electrode density is lowered, which is not preferable.

The negative electrode active material prepared according to the present invention has a high degree of mixing of lithium and vanadium, has excellent crystallinity and conductivity, and exists in a particle sized particle, and thus has excellent life characteristics, capacity characteristics, And efficiency characteristics.

A lithium secondary battery according to another embodiment of the present invention includes a negative electrode, a positive electrode, and an electrolyte.

The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

The negative electrode active material is the same as described above.

The negative electrode may be prepared by mixing the negative electrode active material, the binder, and optionally the conductive agent in a solvent to prepare a composition for forming a negative electrode active material layer, and then applying the composition to a negative electrode current collector. Since such an electrode manufacturing method is well known in the art, detailed description thereof will be omitted.

The binder adheres the anode active material particles to each other well, and also serves to adhere the anode active material to the current collector well, and representative examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, and polyvinyl chloride. , Polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene may be used, but is not limited thereto.

The conductive agent is used to impart conductivity, and any battery can be used as long as it is an electronic conductive material without causing chemical change in the battery to be constructed. Examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, and ketjen black. , Metal powders such as carbon fiber, copper, nickel, aluminum, silver, or metal fibers, and the like, and also conductive materials such as polyphenylene derivatives can be mixed and used.

N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

The cathode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof. have.

The positive electrode includes a current collector and a cathode active material layer formed on the current collector. As the positive electrode active material, a compound (lithiated intercalation compound) capable of reversible intercalation and deintercalation of lithium may be used. Specifically, at least one of a complex oxide of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used, and more preferably, a compound represented by any one of the following Chemical Formulas 3 to 26 may be used: have:

[Formula 3]

Li _a A _{1 - b} B _b D ₂

(Wherein 0.95 ≦ a ≦ 1.1, and 0 ≦ b ≦ 0.5)

[Formula 4]

Li _a E _{1 - b} B _b O _{2 - c} F _c

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05)

[Formula 5]

LiE _{2 - b} B _b O _{4 - c} F _c

(Wherein 0 ≦ b ≦ 0.5 and 0 ≦ c ≦ 0.05)

[Formula 6]

Li _a Ni _{1 -b- c} Co _b B _c D _α

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2)

[Formula 7]

Li _a Ni _{1 -b- c} Co _b B _c O _{2 -α} F _α

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2)

[Formula 8]

Li _a Ni _{1 -b- c} Co _b B _c O _{2 -α} F ₂

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2)

[Formula 9]

Li _a Ni _{1 -b- c} Mn _b B _c D _α

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2)

[Formula 10]

Li _a Ni _{1 -b- c} Mn _b B _c O _{2 -α} F ₂

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2)

[Formula 11]

Li _a Ni _{1 -b- c} Mn _b B _c O _{2 -α} F _α

(Wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2)

[Formula 12]

Li _a Ni _b E _c G _d O ₂

(Wherein 0.90 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, and 0.001 ≦ d ≦ 0.1.)

[Formula 13]

Li _a Ni _b Co _c Mn _d GeO ₂

(Wherein 0.90 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and 0.001 ≦ e ≦ 0.1).

[Formula 14]

Li _a NiG _b O ₂

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 15]

Li _a CoG _b O ₂

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 16]

Li _a MnG _b O ₂

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 17]

Li _a Mn ₂ G _b O ₄

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 18]

QO ₂

[Formula 19]

QS ₂

[Formula 20]

LiQS ₂

[Formula 21]

V ₂ O ₅

[Formula 22]

LiV ₂ O ₅

[Formula 23]

LiIO ₂

[Formula 24]

LiNiVO ₄

[Formula 25]

Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 3)

[Formula 26]

Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2)

In Chemical Formulas 3 to 26, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof;

B is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof;

D is selected from the group consisting of O, F, S, P, and combinations thereof;

E is selected from Co, Mn, and combinations thereof;

F is selected from the group consisting of F, S, P, and combinations thereof;

G is Al or an element selected from the group consisting of Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof;

Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof;

I is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof;

J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

Of course, what has a coating layer on the surface of this compound can also be used, or the compound and the compound which have a coating layer can also be used in mixture. The coating layer may comprise at least one coating element compound selected from the group consisting of oxides of the coating elements, hydroxides, oxyhydroxides of the coating elements, oxycarbonates of the coating elements and hydroxycarbonates of the coating elements. . The compounds constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof may be used. The coating layer forming process may use any coating method as long as it can be coated with the above compounds by a method that does not adversely affect the physical properties of the positive electrode active material (for example, spray coating or dipping method). Detailed descriptions thereof will be omitted since they can be understood by those skilled in the art.

Like the negative electrode, the positive electrode may be prepared by mixing the positive electrode active material, the binder, and the conductive agent in a solvent to prepare a composition for forming a positive electrode active material layer, and then applying the composition for forming the positive electrode active material layer to a positive electrode current collector. .

Aluminum may be used as the anode current collector, and N-methylpyrrolidone may be used as the solvent, but the cathode current collector and the solvent are not limited thereto.

Since such an electrode manufacturing method is well known in the art, detailed description thereof will be omitted.

As the conductive agent, any battery can be used as long as it is an electronic conductive material without causing chemical change, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, and aluminum. And metal powders such as silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives can be used alone or in combination of one or more thereof.

As the binder, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene may be used. It may be, but is not limited thereto.

N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

In the nonaqueous electrolyte secondary battery of the present invention, the nonaqueous electrolyte includes a nonaqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the cell can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent may be used.

As the carbonate solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) and the like can be used, and the ester solvent is n-methyl acetate, n-ethyl acetate, n-propyl acetate, dimethyl Acetate, methylpropionate, ethylpropionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like can be used. As the ether, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used, and cyclohexanone may be used as the ketone solvent. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol solvent, and the aprotic solvent may be R-CN (R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms. Amides such as nitriles, dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, and the like.

The non-aqueous organic solvent may be used alone or in combination of one or more, and the mixing ratio in the case of mixing one or more may be appropriately adjusted according to the desired battery performance, which is widely understood by those skilled in the art. Can be.

In the case of the carbonate solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of 1: 1 to 1: 9, so that the performance of the electrolyte may be excellent.

The non-aqueous organic solvent of the present invention may further include an aromatic hydrocarbon organic solvent in the carbonate solvent. In this case, the carbonate solvent and the aromatic hydrocarbon organic solvent may be mixed in a volume ratio of 1: 1 to 30: 1.

As the aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound represented by Formula 27 may be used.

[Formula 27]

(In the above formula 27, R ₁ to R ₆ are each independently selected from the group consisting of hydrogen, halogen, alkyl group of 1 to 10 carbon atoms, haloalkyl group and combinations thereof.)

Preferred aromatic hydrocarbon organic solvents are benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2, 4-trichlorobenzene, iodobenzene, 1,2-dioodobenzene, 1,3-dioodobenzene, 1,4-dioiobenzene, 1,2,3-triiodobenzene, 1,2,4 -Triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 -Trichlorotoluene, iodotoluene, 1,2-dioodotoluene, 1,3-diodotoluene, 1,4-diao Toluene, to which 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, and selected from the group consisting of a combination of lead.

The non-aqueous electrolyte may further include a life improving additive such as vinylene carbonate or fluoroethylene carbonate in order to improve battery life. In the case of further using such life improving additives, the amount thereof can be properly adjusted.

The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery and to promote the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of such lithium salts are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x +1} SO ₂ ) (C _y F _{2y +1} SO ₂ ), where x and y are natural numbers, LiCl, LiI, and lithium bisoxal One or more selected from the group consisting of lithium bisoxalate borate is included as a supporting electrolytic salt.

The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. If the concentration of the lithium salt is less than 0.1M, the conductivity of the electrolyte is lowered, the performance of the electrolyte is lowered, if it exceeds 2.0M there is a problem that the mobility of the lithium ion is reduced by increasing the viscosity of the electrolyte.

The separator may exist between the positive electrode and the negative electrode according to the type of the lithium secondary battery. As the separator, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / It goes without saying that a mixed multilayer film such as a polypropylene three-layer separator can be used.

An example of the lithium secondary battery of the present invention having the above-described configuration is shown in FIG. 3. 3 illustrates an electrode group 110 in which the cathode 113 and the anode 112 are positioned with the separator 114 interposed therebetween, and a case 120 having an opening formed at one end thereof to accommodate the electrode group together with the electrolyte. ). In addition, the opening of the case shows a lithium secondary battery 100 in which a cap assembly 140 for sealing the case 120 is installed.

Of course, the lithium secondary battery of the present invention is not limited to this formation, and any shape such as a square, a pouch, etc., including the negative electrode active material of the present invention and capable of operating as a battery, is of course possible.

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

(Example 1)

Li ₂ C ₂ O ₄ , VOCl ₃ , and Cr ₂ (SO ₄ ) ₃ .H ₂ O are mixed with a solvent so that the molar ratio of lithium, vanadium, and Cr is 1.1: 0.85: 0.05, and the mixture is Ethylenediaminetetraacetic acid, an amine compound, was added so that the lithium salt and the amine compound had a molar ratio of 1: 6. Subsequently, 6 mol of (CH ₃ ) ₄ NOH was added to prepare a complex compound solution. The complex solution was dried in a drying oven at 90 ° C. by vacuum to form a negative electrode active material precursor in a gel state. The negative electrode active material precursor was calcined under nitrogen gas at a temperature of 1000 ° C. to prepare a Li _1.1 (V, Cr) _0.9 O ₂ negative electrode active material having an average particle diameter of 10 μm to 20 μm.

(Example 2)

A negative electrode active material was prepared in the same manner as in Example 1 except that the amine compound was changed to tetramethylethylenediamine.

(Example 3)

A negative electrode active material was prepared in the same manner as in Example 1 except that the amine compound was changed to tetramethylpropylenediamine.

(Example 4)

A negative electrode active material was prepared in the same manner as in Example 1 except that VOCl ₃ was changed to V0SO ₄ .

(Example 5)

VOCl ₃ to V0Cl ₃ A negative electrode active material was prepared in the same manner as in Example 1 except that the hydrate was changed.

(Example 6)

To and is carried out in the same manner as in Example 1 except for changing the VOCl ₃ as V0SO ₄ hydrate, to prepare a negative electrode active material.

(Example 7)

Li ₂ C ₂ O ₄ A negative electrode active material was prepared in the same manner as in Example 1, except that Li ₂ SO ₄ was changed.

(Example 8)

A negative electrode active material was prepared in the same manner as in Example 1 except that Li ₂ C ₂ O ₄ was changed to LiNO ₃ .

(Example 9)

Li ₂ C ₂ O ₄ to Li ₂ SO ₄ A negative electrode active material was prepared in the same manner as in Example 1 except that the hydrate was changed.

(Example 10)

A negative electrode active material was prepared in the same manner as in Example 1 except that Li ₂ C ₂ O ₄ was changed to LiOH.

(Example 11)

As in Example 1, except that Li ₂ C ₂ O ₄ , VOCl ₃ , and MnSO ₄ · H ₂ O were mixed with a solvent so that the molar ratio of lithium, vanadium, and Mn was 1.1: 0.8: 0.1. The negative electrode active material was prepared.

(Example 12)

A negative active material was prepared in the same manner as in Example 1 except that Li ₂ C ₂ O ₄ and VOCl ₃ were mixed in a solvent such that a molar ratio of lithium and vanadium was 1.2: 0.8.

(Comparative Example 1)

LiOH And The V ₂ O ₃ 1.1: mixed in a ratio of 0.45 was pulverized, and then subjected to the calcination step of heat treatment at 900 ℃, by screening, to prepare a Li _{1 .1} V _{0 .9} O ₂ negative active material.

Charging and discharging  Capacity measurement

After preparing a coin cell using the negative electrode active material prepared according to Examples 1 to 12, and Comparative Example 1, each coin cell was charged and discharged at 0.1C once to perform a chemical conversion process, and charged and discharged at 0.5C Was carried out.

For the coin cell, the discharge capacity at the time of one time charge and discharge (meaning that the charge and discharge was performed once after battery formation), and the initial reversible efficiency were measured, and the results of Example 1 and Comparative Example 1 were described below. Table 1 shows.

TABLE 1

Initial discharge capacity (mAh / cc) Initial Reversible Efficiency (%) Example 1 598 85 Comparative Example 1 570 83

Referring to Table 1, the coin cell prepared using the negative electrode active material of Example 1 was superior in initial reversible efficiency compared to the coin cell using the negative electrode active material of Comparative Example 1, in particular, the initial discharge capacity of Example 1 It was much higher than Example 1. In addition, the coin cells of Examples 2 to 12 also exhibited the same initial reversible efficiency and initial discharge capacity as those of Example 1.

Therefore, it was confirmed that the anode active material for a lithium secondary battery according to the present invention has excellent life characteristics and capacity characteristics.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is a flowchart illustrating a method of manufacturing a negative electrode active material for a lithium secondary battery of the present invention.

Figure 2 is a schematic diagram showing the structure of the complex compound produced as an intermediate during the preparation of the negative electrode active material according to an embodiment of the present invention.

3 is a cross-sectional view of a rechargeable lithium battery according to one embodiment of the present invention.

Claims (14)

Mixing a lithium salt, a vanadium salt, an amine compound, and optionally M containing salt in a solvent to form a complex solution; Volatilizing a solvent of the complex solution to form a negative electrode active material precursor; And Method for producing a negative active material for a lithium secondary battery comprising the step of reducing the calcining of the negative electrode active material precursor to prepare a negative electrode active material of the formula (1). [Formula 1] Li _{1 + x} V _{1 -x- y} M _y O _{2 + z} (In the formula 1, 0.01 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.3, -0.2 ≤ z ≤ 0.2, M is composed of transition metals other than vanadium, alkali metals, alkaline earth metals, semimetals, and combinations thereof Element selected from the group.) The method of claim 1, The lithium salt is LiX (X is F, Cl, Br, or I), Li ₂ CO ₃ , LiNO ₃ , Li ₂ SO ₄ , LiOH, Li ₂ C ₂ O ₄ , LiCOOH, LiC ₂ O ₂ H ₃ , And a hydrate thereof, and a combination thereof, a method for producing a negative electrode active material for a lithium secondary battery. The method of claim 1, The vanadium salt is selected from the group consisting of VOCl ₂ , V0Cl ₃ , V0SO ₄ , VCl ₃ , VCl ₄ , hydrates thereof, and combinations thereof. The method of claim 1, The M-containing salt is a method for producing a negative electrode active material for a lithium secondary battery is selected from the group consisting of M-containing hydroxide, hydrate, oxide, nitride, nitrate, carbonate, sulfate, chloride, and combinations thereof. The method of claim 1, The amine compound is selected from the group consisting of alkylenediamine tetraacetic acid, tetraalkylalkylenediamine, and combinations thereof. The method of claim 1, A method of manufacturing a negative active material for a lithium secondary battery, which further comprises adding a basic substance when preparing the complex solution. The method of claim 6, The basic material is a method for producing a negative electrode active material for a lithium secondary battery that is represented by the formula (2). [Formula 2] R _n H _{4 - n} NOH (In Formula 2, R is alkyl and n is 0 ≦ n ≦ 4.) The method of claim 1, The solvent is a method of producing a negative electrode active material for a lithium secondary battery that is selected from the group consisting of water, alcohol, and combinations thereof. The method of claim 1, The reduction calcination step is a method for producing a negative active material for a lithium secondary battery that is carried out at a temperature of 1500 ℃ or less. The method of claim 9, The reduction calcination step is a method for producing a negative active material for a lithium secondary battery that is carried out at a temperature of 400 ℃ to 1300 ℃. The method of claim 1, The reduction calcination step is the primary calcination at 400 ℃ to 700 ℃, and secondary calcination at 700 ℃ to 1300 ℃ manufacturing method of a negative electrode active material for a lithium secondary battery. The method of claim 1, The negative electrode active material is a method for producing a negative electrode active material for a lithium secondary battery having an average particle diameter of 30μm or less. The method of claim 12, The negative electrode active material is a method of producing a negative electrode active material for a lithium secondary battery having an average particle diameter of 0.5μm to 30μm. A negative electrode comprising a negative electrode active material prepared according to any one of claims 1 to 13; A positive electrode including a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions; And Electrolyte Lithium secondary battery comprising a.

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