KR20080093781A - Method of preparing negative active material for rechargeable lithium battery and rechargeable lithium battery including negative active material prepared therefrom - Google Patents

Abstract

A method for preparing a negative electrode active material for a lithium secondary battery, and a lithium secondary battery containing the negative electrode active material are provided to enhance capacity characteristics and lifetime characteristics. A method for preparing a negative electrode active material for a lithium secondary battery comprises the steps of (S1) mixing a lithium salt, a vanadium alkoxide compound or its hydrolyzate and optionally a salt containing M in a solvent to prepare a sol; (S2) ultrasonicating the sol to prepare an aerosol; and (S3) spray heat treating the aerosol to prepare a negative electrode active material represented by Li_(1+x) V_(1-x-y) M_y O_(2+z), wherein 0.01<=x<=0.5; 0<=y<=0.3; -0.2<=z<=0.2; and M is an element selected from the group consisting of a transition metal except vanadium, an alkali metal, an alkaline earth metal, a semimetal and their combination.

Description

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

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

2 is a view schematically showing the structure of a lithium secondary battery of the present invention.

[Industrial use]

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.

[Prior art]

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 that of a battery using an alkaline aqueous solution using an organic electrolyte solution.

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 problem of 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) in the production of the electrode plate, and side reaction with the organic electrolyte used at high discharge voltage is 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 comprises the steps of preparing a sol by mixing lithium salt, vanadium alkoxide or hydrolyzate thereof, and optionally M containing salt in a solvent, sonicating the sol to form droplets, Spray-treating the droplets to prepare a negative active material of Chemical Formula 1 below.

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

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

The lithium vanadium oxide (hereinafter referred to as LVO) anode active material is manufactured by grinding and mixing solid Li ₂ CO ₃ or LiOH with V ₂ O ₃ or V ₂ O ₄ , calcining, and then screening do. 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, the degree of mixing of lithium and vanadium, crystal structure, crystallinity, quantitative ratio of lithium and vanadium, Control of variables related to electrode density such as c / a lattice constant ratio, oxidation number of vanadium, particle shape, and particle size is required.

However, although the crystal structure, crystallinity, lattice constant ratio, and vanadium oxide number can be controlled by the above method, the problem of aggregation of particles at high calcination temperature and the resulting quantitative ratio of lithium and vanadium, particle shape, particle size, etc. Since it is difficult to control, it is difficult to secure capacitive electrochemical properties and reproducibility through electrode density improvement.

In particular, the LiVMO negative electrode active material which improves the conductivity of the existing LVO negative electrode active material is pulverized, mixed and calcined primarily by solid Li ₂ CO ₃ or LiOH as a lithium raw material and V ₂ O ₃ or V ₂ O ₄ as a vanadium raw material. Since the mixture obtained is prepared by a complex process of secondary grinding, mixing, calcining and screening of the MO ₂ oxide, it is more difficult to control the parameters related to the electrode density.

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 and vanadium, particle shape, particle size, the degree of volatilization of lithium, and the degree of oxidation of vanadium are The negative electrode active material for a lithium secondary battery that can be controlled and exhibits high capacity, lifetime, and reproducibility with high crystallinity can be manufactured.

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 sol is prepared by mixing a lithium salt, vanadium alkoxide or a hydrolyzate thereof, and optionally an M-containing salt in a solvent. Step (S1), sonicating the sol to form a droplet (S2), and spray-heat-treating the droplet to prepare a negative electrode active material of the formula (S3).

[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.)

A sol is prepared by mixing lithium salt, vanadium alkoxide or its hydrolyzate, and optionally M containing salt in a solvent (S1).

Representative examples of the lithium salt include LiX (X is F, Cl, Br, or I), LiOH, LiNO ₃ , Li ₂ SO ₄ , Li ₂ C ₂ O ₄ , LiC ₂ O ₂ H _{3 ,} LiCOOH, And hydrates thereof, and those selected from the group consisting of, but is not limited thereto.

The vanadium alkoxide is preferable to have an alkoxy group of C ₁ to C _15, more preferably having an alkoxy group of C ₁ to C _8. Representative examples include vanadium isopropoxide, vanadium methoxide, vanadium ethoxide, vanadium oxytriethoxide (VO (OC ₂ H ₅ ) ₃ ), vanadium oxytriisopropoxide (VO (OCH (CH ₃ ) ₂ ) ₃ ), And it may be selected from the group consisting of a combination thereof, but is not limited thereto. The vanadium alkoxide and the lithium salt may be mixed in a solvent to prepare a sol in which the vanadium alkoxide is hydrolyzed.

In addition, the hydrolyzate of the vanadium alkoxide may be selected from the group consisting of vanadium hydroxide, vanadium oxide, and combinations thereof.

In addition, depending on the desired product, M-containing salts may optionally be further added. The M-containing salt may be selected from the group consisting of M-containing hydroxides, hydrates, oxides, nitrides, nitrates, carbonates, sulfates, chlorides, and combinations thereof. M of the M-containing salt is an element having an ionic radius (0.78 kV) similar to vanadium (III, IV), and may be an octahedral composite structure and an element having an electronic structure similar to vanadium (III, IV). Examples of the M include transition metals other than vanadium, alkali metals, alkaline earth metals, and semimetals (having intermediate properties between nonmetals and metals, 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. M may be substituted with a homogeneous distribution in the lithium vanadium oxide anode active material, thereby improving structural stability of the active material.

The solvent may be selected from the group consisting of water, alcohols, and combinations thereof, and representatively, those selected from the group consisting of water, ethanol, methanol, isopropanol, and combinations thereof may be used.

In addition, when the sol is prepared by mixing the lithium salt, vanadium alkoxide or hydrolyzate thereof, and optionally M-containing salt, a pH adjuster may be further added.

A basic substance may be used as the pH adjusting agent, and representative examples thereof include NH ₃ , NH ₄ OH, NaOH, KOH, and combinations thereof.

It is preferable that it is 7-14, and, as for the said pH, it is more preferable that it is 10-14. In the pH range, the hydrolysis may proceed smoothly, and if it is out of the above range, the hydrolysis is not smooth, and it is not preferable because it is difficult to prepare a sol in which vanadium alkoxide is hydrolyzed.

The lithium salt, vanadium alkoxide or a hydrolyzate thereof, and optionally M-containing salts may be appropriately mixed in a molar ratio between the elements of Formula 1, and may preferably be mixed and used in the following molar ratios.

The lithium salt and the vanadium alkoxide or its hydrolyzate are preferably added such that the molar ratio of lithium and vanadium is 1.01: 0.99 to 1.5: 0.5, and more preferably so as to be 1.1: 0.9 to 1.3: 0.7. Within this range, there is an advantage in that a mono-phase is formed, and if it is out of the above range, an additional second phase may be formed, which is not preferable.

The vanadium alkoxide or its hydrolyzate and M-containing salt are preferably added such 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.

Next, ultrasonic waves are applied to the sol to form droplets (S2).

The droplets are produced by an ultrasonic vibrator. The frequency of the ultrasonic wave is preferably 0.1 to 10 MHz, more preferably 1 to 5 MHz. If the frequency is less than 0.1MHz may be a problem that the droplet is not formed because the energy is small, it is not preferable, if it exceeds 10MHz, it may be difficult to produce a uniform spherical droplet is not preferable.

It is preferable that the said droplet has an average particle diameter of 30 micrometers or less, It is more preferable to have an average particle diameter of 50 nm-30 micrometers, It is still more preferable to have an average particle diameter of 0.1-25 micrometers. When the average particle diameter of the droplet is 30 μm or less, it can be widely used as a battery material of various fields, and the smaller the particle diameter, the more effectively it can be utilized, so there is no need to limit the lower limit of the droplet. However, at present, the average particle diameter of droplets easily obtainable by ultrasonic waves is about 0.1 μm or more, and droplets of 0.1 μm or less that can be produced by ultrasonic waves also belong to the present invention. In addition, when the average particle diameter of the droplets exceeds 30μm, it may be difficult to control the particle size of the negative electrode active material, which is not preferable.

Subsequently, the droplets are spray-treated to prepare a negative electrode active material represented by Chemical Formula 1 (S3).

The spray heat treatment process may be performed by spraying a droplet with a rotary atomizer or a nozzle in a high temperature chamber. At this time, it is preferable that it is 1500 degrees C or less, and, as for the temperature of the said high temperature chamber, it is more preferable that it is 400-1300 degreeC. In addition, the temperature of the high temperature chamber may be 500, 600, 700, 800, 900, 1000, 1100, or 1200 ℃. At this temperature, the degree of volatilization of lithium and the degree of oxidation of vanadium can be controlled to produce a negative electrode active material having a small size. Therefore, the electrode density can be increased, and a negative electrode active material for a lithium secondary battery having improved capacity characteristics and lifespan characteristics can be manufactured. However, at a temperature higher than 1500 ° C., particles may be agglomerated with each other to form a coarse negative active material, which is not preferable. In addition, the spray heat treatment process is preferably carried out for 0.1 to 12 hours, more preferably for 0.1 to 2 hours. In the above range of time, the particle size of the negative electrode active material can be controlled to be small, and if the time is exceeded, the manufacturing cost increases, which is not preferable.

The spray heat treatment step is preferably carried out under an inert gas such as argon, oxygen, or nitrogen.

In the spray heat treatment step, the solvent contained in the droplets is volatilized and calcined at high temperature to prepare a negative electrode active material of the formula (1).

It is preferable that the said negative electrode active material has an average particle diameter of 30 micrometers or less, It is more preferable to have an average particle diameter of 0.1-30 micrometers, It is still more preferable to have an average particle diameter of 0.1-20 micrometers. When the average particle diameter of the negative electrode active material exceeds 30 μm, there is a problem that it is difficult to control the thickness of the battery electrode plate, which is not preferable. If the average particle size is 30 μm or less, there is an advantageous advantage in the production of the electrode plate is preferable.

In addition, the spray heat treatment process may be a first heat treatment at a temperature of 400 to 700 ℃, secondary heat treatment at a temperature of 700 to 1300 ℃. As such, if the heat treatment process is performed at different temperatures in the first and second stages, the crystallinity of the negative electrode active material may be controlled.

In addition, the spray heat treatment process may be carried out further including a drying process. In the drying process, the solvent contained in the droplet sprayed from the rotary atomizer or the nozzle is volatilized.

It is preferable to perform the said drying process at the temperature of 500 degrees C or less, It is more preferable to carry out at the temperature of 70-500 degreeC, It is still more preferable to carry out at the temperature of 70-400 degreeC. In addition, the drying step may be carried out at 120, 170, 220, 270, 320, or 370 ℃. At this temperature, it is preferable to form spherical uniform particles, and if the temperature exceeds 500 ° C., it may not be preferable because a cavity may be formed inside the particle or a problem that spherical particles are difficult to form. In addition, it is preferable to perform the said drying process under inert gas, such as argon gas, oxygen, or nitrogen.

The negative electrode active material according to the manufacturing method of the present invention is excellent in mixing degree, crystallinity, particle atomization, and conductivity of lithium and vanadium, thereby improving the life characteristics, capacity characteristics, and efficiency characteristics of a lithium secondary battery.

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.

As the binder, the negative electrode active material particles adhere well to each other, and the negative electrode active material adheres well to the current collector. Examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, and polyvinyl. Chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene, and the like, 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, and 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 2 to 25 may be used. have:

[Formula 2]

Li _a A _{1 - b} B _b D ₂

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

[Formula 3]

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 4]

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

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

[Formula 5]

Li _a Ni _{1 -b- c} Co _b BcD _α

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

[Formula 6]

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 7]

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 8]

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 9]

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 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 _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 12]

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 13]

Li _a NiG _b O ₂

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

[Formula 14]

Li _a CoG _b O ₂

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

[Formula 15]

Li _a MnG _b O ₂

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

[Formula 16]

Li _a Mn ₂ G _b O ₄

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

[Formula 17]

QO ₂

[Formula 18]

QS ₂

[Formula 19]

LiQS ₂

[Formula 20]

V ₂ O ₅

[Formula 21]

LiV ₂ O ₅

[Formula 22]

LiIO ₂

[Formula 23]

LiNiVO ₄

[Formula 24]

Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 3)

[Formula 25]

Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2)

In Chemical Formulas 2 to 25, 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 does not adversely affect the physical properties of the positive electrode active material by using such elements in the compound (for example, spray coating, dipping, etc.). Details that will be well understood by those in the field will be omitted.

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. Metal powders such as silver and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may 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 Chemical Formula 26 may be used.

[Formula 26]

(In Formula 26, 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. 2. 2 shows a cathode 2, an anode 3, a separator 4 disposed between the cathode 2 and an anode 3, the cathode 2, the anode 3, and the separator 4. The lithium secondary battery 1 which consists of the electrolyte solution impregnated in, the battery container 5, and the sealing member 6 which encloses the battery container 5 as a main part is shown.

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. Such following examples are only one preferred embodiment of the present invention, and the present invention is not limited to the following examples.

(Example 1)

LiNO ₃ , vanadium isopropoxide (VO (OC ₃ H ₇ ) ₃ ), and Cr ₂ (SO ₄ ) ₃ .H ₂ O were dissolved in water so that the molar ratio of lithium, vanadium, and Cr was 1.1: 0.8: 0.1. The mixture was hydrolyzed and the pH was adjusted to 12 by the addition of NH ₃ , a pH regulator, to form a sol in which lithium ions surround the surface of vanadium hydroxide. The sol was sprayed with ultrasonic vibration of 2.54 MHz to form droplets having an average particle diameter of 20 μm. Forming a group with less liquid spray-dried powder at 400 ℃ temperature in a nitrogen atmosphere, and then an average particle diameter 20㎛ by heating the powder to _{1000 ℃ Li 1 .1 (V,} Cr) to prepare a _0.9 O ₂ negative active material It was.

(Example 2)

LiNO ₃ and the vanadium isopropoxide in a molar ratio of lithium and vanadium 1.2: ₁ and has an average particle diameter of Li 20㎛ conducted in the same manner as in Example 1 except that the mixing of the water so that 0.8 _.2 V _{0 .8} An O ₂ negative electrode active material was prepared.

(Example 3)

LiOH, vanadium methoxide, and Mg (NO ₃ ) ₂ was carried out in the same manner as in Example 1 except that the molar ratio of lithium, vanadium, and Mg was mixed in water such that the molar ratio of 1.1: 0.8: 0.1 was 20. ㎛ of Li _{1 .1} (V, Mg) to prepare a _0.9 O ₂ negative active material.

(Example 4)

Li ₂ SO _{4 ,} vanadium ethoxide, And An anode active material was prepared in the same manner as in Example 1 except that Mg (NO ₃ ) ₂ was mixed in water such that a molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1.

(Example 5)

Same as Example 1 except that Li ₂ SO _{4 ,} vanadium oxytriethoxide, and Mg (NO ₃ ) ₂ were mixed in water such that the molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1. The negative electrode active material was prepared.

(Example 6)

Li ₂ SO ₄ , vanadium oxytriisopropoxide, and An anode active material was prepared in the same manner as in Example 1 except that Mg (NO ₃ ) ₂ was mixed in water such that a molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1.

(Example 7)

LiOH.H ₂ O _, vanadium oxytriisopropoxide, and An anode active material was prepared in the same manner as in Example 1 except that Mg (NO ₃ ) ₂ was mixed in water such that a molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1.

(Example 8)

LiNO ₃ H ₂ O _, vanadium oxytriisopropoxide, and An anode active material was prepared in the same manner as in Example 1 except that Mg (NO ₃ ) ₂ was mixed in water such that a molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1.

(Example 9)

_{Li 2 SO 4 · H 2 O} , oxy vanadium triisopropoxide, and An anode active material was prepared in the same manner as in Example 1 except that Mg (NO ₃ ) ₂ was mixed in water such that a molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1.

(Example 10)

Example 1 except that LiC ₂ O ₂ H ₃ , vanadium oxytriisopropoxide, and Mg (NO ₃ ) ₂ were mixed in water such that the molar ratio of lithium, vanadium, and Mg was 1.1: 0.8: 0.1. In the same manner as in the preparation of the negative electrode active material.

(Example 11)

LiCOOH, vanadium oxytriisopropoxide, and Mg (NO ₃ ) ₂ was carried out in the same manner as in Example 1 except that the mixture of lithium, vanadium, and Mg in water so that the molar ratio of 1.1: 0.8: 0.1 A negative electrode active material was prepared.

(Example 12)

A negative electrode active material was prepared in the same manner as in Example 1 except that ethanol was used as the solvent.

(Example 13)

A negative electrode active material was prepared in the same manner as in Example 1 except that isopropanol was used as the solvent.

(Example 14)

A negative electrode active material was prepared in the same manner as in Example 1 except that methanol was used as the solvent.

(Example 15)

LiNO ₃ , vanadium isopropoxide (VO (OC ₃ H ₇ ) ₃ ), and Cr ₂ (SO ₄ ) ₃ H ₂ O are mixed in water so that the molar ratio of lithium, vanadium, and Cr is 1.3: 0.7: 0.2 A negative electrode active material was prepared in the same manner as in Example 1 except that one was prepared.

(Example 16)

LiNO ₃ , vanadium isopropoxide (VO (OC ₃ H ₇ ) ₃ ), and Cr ₂ (SO ₄ ) ₃ H ₂ O were dissolved in water so that the molar ratio of lithium, vanadium, and Cr was 1.01: 0.7: 0.1. A negative electrode active material was prepared in the same manner as in Example 1 except for mixing.

(Comparative Example 1)

The solid phase of LiOH and V ₂ O ₃ 1.1: pulverizing a mixture at a molar ratio of 0.45, and then subjected to the calcination step of heat treatment at 900 ℃, were screened by preparing a Li _{1 .1} V _{0 .9} O ₂ negative active material.

Discharge capacity and initial reversible efficiency measurement

After preparing a coin cell using the negative electrode active material prepared according to Examples 1 to 16 and Comparative Example 1, each coin cell was charged and discharged at 0.1C once to carry out a chemical conversion process, and charged and discharged at 0.5C. Was carried out.

With respect to the coin cell, the discharge capacity at the time of charging / discharging once (refering to charging and discharging once after battery formation) and initial reversible efficiency were measured, and the results of Examples 1 to 3 and Comparative Example 1 were measured. It is shown in Table 1 below.

TABLE 1

Initial Discharge Capacity (mAh / cc) Initial Reversible Efficiency (%) Example 1 604 86 Example 2 600 85 Example 3 605 85 Comparative Example 1 570 83

Referring to Table 1, the coin cell using the negative electrode active material of Examples 1 to 3 manufactured by the manufacturing method of the present invention is superior in the initial discharge capacity and initial reversible efficiency than the coin cell using the negative electrode active material of Comparative Example 1 I could confirm it. Moreover, about the coin cell of Examples 4-16, the initial discharge capacity and initial reversible efficiency of the level equivalent to Examples 1-3 were confirmed.

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.

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

Claims (21)

Mixing a lithium salt, vanadium alkoxide or its hydrolyzate, and optionally M containing salt in a solvent to prepare a sol; Sonicating the sol to form droplets; And Spray-treating the droplets to prepare a negative active material for a lithium secondary battery of Formula 1 Method for producing a negative electrode active material for a lithium secondary battery comprising a. [Formula 1] Li _{1 + x} V _{1 -x- y} M _y O _{2 + z} In the above formula, 0.01≤x≤0.5, 0≤y≤0.3, -0.2≤z≤0.2, M is in the group consisting of transition metals other than vanadium, alkali metals, alkaline earth metals, semimetals, and combinations thereof Element to be selected) The method of claim 1, The lithium salt is LiX (X is F, Cl, Br, or I), LiOH, LiNO ₃ , Li ₂ SO ₄ , Li ₂ C ₂ O ₄ , LiC ₂ O ₂ H _3, LiCOOH, and hydrates thereof, and The manufacturing method of the negative electrode active material for lithium secondary batteries chosen from the group which consists of these combinations. The method of claim 1, The vanadium alkoxide includes vanadium isopropoxide, vanadium methoxide, vanadium ethoxide, vanadium oxytriethoxide (VO (OC ₂ H ₅ ) ₃ ), vanadium oxytriisopropoxide (VO (OCH (CH ₃ )). ₂ ) ₃ ) and a method for producing a negative electrode active material for a lithium secondary battery which is selected from the group consisting of these. The method of claim 1, The hydrolyzate of the vanadium alkoxide is selected from the group consisting of vanadium hydroxide, vanadium oxide, 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 containing M, which is an element selected from the group consisting of transition metals other than vanadium, alkali metals, alkaline earth metals, semimetals, and combinations thereof. The method of claim 5, 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, carbonate, sulfate, chloride, and combinations thereof. 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 7, wherein The solvent is a method of producing a negative electrode active material for a lithium secondary battery. The method of claim 1, The lithium salt, vanadium alkoxide or a hydrolyzate thereof, and optionally a M-containing salt in the preparation of the sol, when the sol is prepared, a pH adjusting agent is further added. The method of claim 9, The pH adjusting agent is a method for producing a negative active material for a lithium secondary battery that is a basic material. The method of claim 10, The pH adjusting agent is selected from the group consisting of NH ₃ , NH ₄ OH, NaOH, KOH, and combinations thereof. The method of claim 1, The ultrasonic wave is a method of manufacturing a negative electrode active material for a lithium secondary battery having a frequency of 0.1 to 10MHz. The method of claim 12, The ultrasonic wave is a method of manufacturing a negative electrode active material for a lithium secondary battery having a frequency of 1 to 5MHz. The method of claim 1, The droplet is a method of producing a negative electrode active material for a lithium secondary battery having an average particle diameter of 30μm or less. The method of claim 1, The said spray heat treatment process is a manufacturing method of the negative electrode active material for lithium secondary batteries which is performed at the temperature of 1500 degrees C or less. The method of claim 15, The spray heat treatment 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 said spray heat treatment process is a manufacturing method of the negative electrode active material for lithium secondary batteries which is performed under inert gas. The method of claim 1, The spray heat treatment step is a method for producing a negative electrode active material for a lithium secondary battery further comprising a drying step. The method of claim 18, The said drying process is a manufacturing method of the negative electrode active material for lithium secondary batteries which is performed at the temperature of 500 degrees C or less. 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 30 μm or less. A negative electrode comprising a negative electrode active material prepared according to any one of claims 1 to 20; 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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