KR20150062837A - Negative electrode active material for a lithium rechargable battery including metal oxide and carbon nano fiber, methode for synthesising the same, and a lithium rechargable battery including the same - Google Patents

Abstract

The present invention relates to: a negative electrode active material for a lithium secondary battery, wherein a metal oxide represented by Chemical Formula 1 and a carbon nano fiber disposed on the surface of the metal oxide are included; a method for producing the same; and a lithium secondary battery including the same. [Chemical Formula 1] M_xO_y In Chemical Formula 1, M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof, and x:y is 1:0.5 to 1:2.

Description

TECHNICAL FIELD The present invention relates to a negative electrode active material for a lithium secondary battery including a metal oxide and a carbon nanofiber, a method for producing the same, and a lithium secondary battery including the metal oxide and the carbon nanofiber, and a lithium secondary battery including the metal oxide and the carbon nanofiber. AND A LITHIUM RECHARGABLE BATTERY INCLUDING THE SAME}

The present invention relates to a negative electrode active material for a lithium secondary battery including a metal oxide and a carbon nanofiber, a method for producing the same, and a lithium secondary battery comprising the same.

Lithium secondary batteries have been attracting attention as power sources for driving electronic devices.

Graphite is mainly used as an anode material of a lithium secondary battery. However, since the capacity per unit mass of graphite is as small as 372 mAh / g, it is difficult to realize the high capacity of the lithium secondary battery.

Examples of the anode material exhibiting a higher capacity than graphite include an alloy system such as silicon, tin and germanium, and an oxide system. These materials have the advantage of realizing high capacity and miniaturization of the battery. However, these alloy or metal oxide based cathode materials have a large internal tension when combined with lithium. Thereby causing a loss of capacity due to pulverization during the charging / discharging process.

Transition metal oxides have been studied as another anode material. The transition metal oxide has a theoretical capacity of 700 to 1000 mAh / g, which is low in price and high in safety during charging and discharging. However, these transition metal oxides generate Li ₂ O and form nano-sized metal particles during charging and discharging. As a result, there is a problem that the irreversible capacity of the battery increases and the battery characteristics deteriorate.

The present invention provides a negative active material for a lithium secondary battery excellent in electric conductivity and excellent in charge / discharge characteristics, high rate characteristics and life characteristics, and a method for producing the same, and a lithium secondary battery comprising the same.

In one embodiment of the present invention, there is provided a negative active material for a lithium secondary battery comprising a metal oxide represented by the following Chemical Formula 1 and carbon nanofibers located on the surface of the metal oxide.

[Chemical Formula 1]

M _x O _y

In the above formula (1), M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof; x: y is 1: 0.5 to 1: 2.

The carbon nanofibers may be grown on the surface of the metal oxide.

In Formula 1, M may be Ni, Mn, Co, or a combination thereof. Specifically, M may be a combination of Ni, Mn, and Co.

For example, the formula (1) may be represented by the following formula (2).

(2)

(Ni _a Co _b Mn _c ) _x O _y

0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1, and x: y are from 1: 0.5 to 1: 2.

The particle size of the metal oxide may be 1 탆 to 50 탆

The diameter of the carbon nanofibers may be 10 nm to 70 nm.

The negative electrode active material for a lithium secondary battery may be spherical.

The particle size of the negative electrode active material for a lithium secondary battery may be 1 탆 to 50 탆.

In another embodiment of the present invention, there is provided a process for preparing a metal hydroxide, Heat treating the metal hydroxide to obtain a metal oxide represented by the following formula (1); And supplying a carbon source to the metal oxide to form carbon nanofibers on the surface of the metal oxide. The present invention also provides a method for manufacturing a negative electrode active material for a lithium secondary battery.

(11)

M (OH) _n

In Formula 11, M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof.

[Chemical Formula 1]

M _x O _y

In the above formula (1), M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof; x: y is 1: 0.5 to 1: 2.

For example, Formula 11 may be represented by Formula 12, and Formula 1 may be represented by Formula 2 below.

[Chemical Formula 12]

Ni _a Co _b Mn _c (OH) _n

0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1,

(2)

(Ni _a Co _b Mn _c ) _x O _y

0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1, and x: y are from 1: 0.5 to 1: 2.

The step of preparing the metal hydroxide of the above formula (11) can be carried out by coprecipitation. Specifically, the step of preparing the metal hydroxide of Formula 11 includes the steps of preparing a metal aqueous solution by adding a metal raw material to a solvent, stirring the metal aqueous solution, and drying the precipitate obtained in the step .

In the step of preparing the metal aqueous solution, a precipitant and / or a chelating agent may be further added.

The step of heat-treating the metal hydroxide to obtain the metal oxide of Formula 1 may be performed at 500 ° C to 800 ° C.

The particle size of the metal oxide obtained may be 1 탆 to 50 탆.

The method for producing a negative electrode active material for a lithium secondary battery according to the present invention comprises the steps of: heat treating the metal hydroxide to obtain a metal oxide represented by Chemical Formula 1, and then reducing the metal oxide to form a metal seed on a surface of the metal oxide As shown in FIG.

In the step of supplying the carbon source to the metal oxide to form the carbon nanofiber on the surface of the metal oxide, the carbon nanofiber may be grown on the surface of the metal oxide.

The carbon raw material may be a gas-phase carbon-based material.

The step of supplying the carbon source to the metal oxide to form the carbon nanofibers on the surface of the metal oxide may be performed at 500 ° C to 800 ° C.

The diameter of the carbon nanofibers may be 10 nm to 70 nm.

The obtained negative electrode active material for a lithium secondary battery may be spherical.

The obtained negative electrode active material for lithium secondary battery may have a particle diameter of 1 탆 to 50 탆.

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

The negative electrode active material according to one embodiment and the lithium secondary battery including the negative electrode active material have excellent electric conductivity and excellent charge / discharge characteristics, high rate characteristics and life characteristics.

Figure 1 is a scanning electron micrograph of the metal hydroxide precursor of Example 1;
2 is a scanning electron micrograph of the negative electrode active material of Example 1. Fig.
FIG. 3 is a transmission electron micrograph of a carbon nanofiber portion taken from the negative electrode active material of Example 1. FIG.
4 is a Fourier transform pattern of a carbon nanofiber portion in the negative electrode active material of Example 1. FIG.
5 is a voltage profile for the cell of Example 1. Fig.
6 is a graph showing the life characteristic evaluation of the battery of Example 1. Fig.
7 is a graph showing the evaluation of the characteristics of the high-fat characteristics of the cell of Example 1. Fig.

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

In one embodiment of the present invention, there is provided a negative active material for a lithium secondary battery comprising a metal oxide represented by the following Chemical Formula 1 and carbon nanofibers located on the surface of the metal oxide.

[Chemical Formula 1]

M _x O _y

In the above formula (1), M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof; x: y is 1: 0.5 to 1: 2.

Specifically, in one embodiment, there can be provided a negative active material for a lithium secondary battery comprising the metal oxide represented by Formula 1 and the carbon nanofibers grown on the surface of the metal oxide.

The negative electrode active material has an excellent electrical conductivity and can realize a high capacity of the battery while improving the charge-discharge characteristic and the life characteristic.

The negative electrode active material may have a shape in which carbon nanofibers are grown on the surface while maintaining a spherical shape. In this case, the negative electrode active material may exhibit excellent battery characteristics.

In the above formula (1), x is the molar ratio of the metal M and y is the mole ratio of the oxygen O. The oxidation number of the metal M may be +1 to +4. Accordingly, the ratio of x and y can be appropriately adjusted within the range of 1: 0.5 to 1: 2, specifically 1: 1 to 1: 2.

The metal oxide represented by Formula 1 may be a transition metal oxide. Specifically, in Formula 1, M must contain Ni, Mn, Co, or a combination thereof, and may optionally include Fe, Al, Mg, Zn, Ti, or combinations thereof.

That is, the metal oxide represented by Formula 1 may be a nickel-based oxide; Manganese based oxides; Cobalt oxide; Or oxides of two or more metals selected from nickel, manganese, and cobalt.

For example, M in the formula (1) includes both Ni, Mn, and Co, and may optionally include Fe, Al, Mg, Zn, Ti, or combinations thereof. That is, the metal oxide represented by Formula 1 may be a nickel manganese cobalt oxide. In this case, the content of nickel, manganese, and cobalt can be appropriately adjusted depending on the application.

The formula (1) may be represented by the following formula (2).

(2)

(Ni _a Co _b Mn _c ) _x O _y

0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1 and x: y is 1: 0.5 to 1: 2 in the above formula (2).

a is molar ratio of nickel, b is molar ratio of cobalt, and c is molar ratio of manganese. Within this range, the ratio of a, b, and c can be appropriately adjusted.

Specifically, 0 <a? 0.7, 0 <a? 0.6, 0 <a? 0.5, 0 <a? 0.4, 0.1? A? 0 <b? 0.6, 0? B? 0.5, 0 <b? 0.4 and 0.1? B? 0.5, 0 <c? 0.7, 0 <c? 0.6, 0 <c? 0.5, 0 < c? 0.4, 0.1? C? 0.5.

The metal oxide may be spherical.

The particle size of the metal oxide may be 1 탆 to 50 탆, specifically 1 탆 to 40 탆, 1 탆 to 30 탆, 10 탆 to 50 탆, 10 탆 to 40 탆, and 10 탆 to 30 탆. In this case, the negative electrode active material can realize excellent battery characteristics.

The carbon nanofibers located on the surface of the metal oxide may be herringbone-type.

The carbon nanofibers may be amorphous carbon nanofibers.

The diameter of the carbon nanofibers may be 10 nm to 70 nm, specifically 10 nm to 60 nm, 10 nm to 50 nm, and 10 nm to 40 nm. In this case, the negative electrode active material exhibits excellent conductivity and can improve the characteristics of the battery.

The length of the carbon fibers may be about 1 to 10 mu m. In this case, the negative electrode active material exhibits excellent conductivity and can improve the characteristics of the battery.

The particle size of the negative electrode active material may be 1 탆 to 50 탆, specifically 1 탆 to 40 탆, 1 탆 to 30 탆, 10 탆 to 50 탆, 10 탆 to 40 탆, and 10 탆 to 30 탆. In this case, the negative electrode active material can improve the characteristics of the battery.

According to another embodiment of the present invention, there is provided a method of manufacturing the negative electrode active material. Specifically, in one embodiment, preparing a metal hydroxide of the formula (11) Heat treating the metal hydroxide to obtain a metal oxide represented by the following formula (1); And supplying a carbon source to the metal oxide to form carbon nanofibers on the surface of the metal oxide. The present invention also provides a method for manufacturing a negative electrode active material for a lithium secondary battery.

(11)

M (OH) _n

In Formula 11, M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof.

[Chemical Formula 1]

M _x O _y

In the above formula (1), M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof; x: y is 1: 0.5 to 1: 2.

The description of Formula 1 is as described above.

The description of M in the formula (11) is the same as that described in the formula (1).

The metal hydroxide of Formula 11 may be selected from the group consisting of nickel-based hydroxides; Manganese based hydroxides; Cobalt based hydroxides; Or a hydroxide of two or more metals selected from nickel, manganese, or cobalt.

More specifically, the metal hydroxide represented by Formula 11 may be nickel manganese cobalt hydroxide. In this case, the content of nickel, manganese, and cobalt can be appropriately adjusted depending on the application.

The formula (11) may be represented by the following formula (12).

[Chemical Formula 12]

Ni _a Co _b Mn _c (OH) _n

In the formula (12), 0 < a 0.85, 0 < b 0.85, 0 < c 0.85, 0.9 a + b + c 1.11, The ratios of a, b, and c can be appropriately adjusted, and the ranges of a, b, and c are the same as those described in Formula 2 above.

The step of preparing the metal hydroxide of the above formula (11) can be carried out by coprecipitation.

Specifically, the step of preparing the metal hydroxide of Formula 11 includes the steps of preparing a metal aqueous solution by adding a metal raw material to a solvent, stirring the metal aqueous solution, and drying the precipitate obtained in the step .

In the step of preparing the metal aqueous solution, a precipitant and / or a chelating agent may be further added.

The precipitant may serve to accelerate the precipitation of the metal hydroxide, which is a precursor of the negative electrode active material, in the aqueous metal solution. The molar ratio of the precipitant to the metal aqueous solution may be from 1: 1 to 1: 5, specifically from 1: 1 to 1: 4, from 1: 1 to 1: 3. In this case, the metal hydroxide can be effectively precipitated to increase the yield.

The chelating agent may be used without limitation as long as it is compatible, and the molar ratio of the chelating agent to the metal aqueous solution may be 1: 0.1 to 1: 2, 1: 0.1 to 1: 1.5. In this case, the yield of the metal hydroxide can be increased.

In the step of stirring the metal aqueous solution, the stirring speed may be 500 to 2000 rpm, 500 to 1800 rpm, 500 to 1600 rpm, and 1000 to 1800 rpm.

The metal hydroxide of Formula 11 may be prepared at 4 to 80 ° C, 4 to 70 ° C, 10 to 80 ° C, 10 to 70 ° C, 25 to 80 ° C, and may be carried out in an air atmosphere or a nitrogen atmosphere .

The step of drying the precipitate may be carried out at 60 to 120 ° C.

The metal hydroxide thus produced can have a uniform particle size distribution and a spherical shape.

The step of heat-treating the metal hydroxide to obtain the metal oxide of Formula 1 may be conducted in an air atmosphere, and may be performed at 500 ° C to 800 ° C, 500 ° C to 700 ° C, and 600 ° C to 800 ° C. In this case, a metal oxide having a uniform particle size distribution can be obtained at a high yield.

The obtained metal oxide may have a particle diameter of 1 탆 to 50 탆, specifically 1 탆 to 40 탆, 1 탆 to 30 탆, 10 탆 to 50 탆, 10 탆 to 40 탆 and 10 탆 to 30 탆. In this case, the negative electrode active material can realize excellent battery characteristics.

The method for producing a negative electrode active material for a lithium secondary battery according to the present invention includes a step of reducing the metal oxide to form a metal seed on a surface of the metal oxide after the metal hydroxide is heat- Step &lt; / RTI &gt;

The metal seed forming step may be performed by heat treating the metal oxide of Formula 1 in a reducing atmosphere.

At this time, the heat treatment temperature may be 500 ° C. to 800 ° C., 500 ° C. to 700 ° C., and 600 ° C. to 800 ° C.

The reducing atmosphere may be an inert gas atmosphere such as argon or a vacuum atmosphere.

When the metal oxide is reduced as described above, the surface of the metal oxide may be partially reduced and exist in the form of a metal, which becomes a metal seed.

The metal seed may be Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof. Specifically, the metal seed may be Ni, Mn, Co, or a combination thereof.

In the step of supplying the carbon source to the metal oxide to form the carbon nanofiber on the surface of the metal oxide, the carbon nanofiber may be grown on the surface of the metal oxide.

That is, the method may include a step of growing a carbon nanofiber on the surface of the metal oxide by supplying a carbon source to the metal oxide after obtaining the metal oxide represented by the formula (1).

At this time, the metal seed may serve as a catalyst for growing carbon nanofibers.

The step of forming carbon nanofibers on the surface of the metal oxide may be performed by a vapor phase method. That is, the carbon nanofibers can be grown on the surface of the metal oxide by supplying a gas-phase carbon material to the metal oxide.

The gaseous carbonaceous material may be at least one selected from the group consisting of acetylene, carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, .

The step of forming the carbon nanofibers on the surface of the metal oxide may be performed in an inert gas atmosphere or a vacuum atmosphere, and may be performed at 500 ° C to 800 ° C, 500 ° C to 700 ° C, and 600 ° C to 800 ° C.

The diameter of the carbon nanofiber thus formed may be 10 nm to 70 nm, specifically 10 nm to 60 nm, 10 nm to 50 nm, and 10 nm to 40 nm. In this case, the negative electrode active material exhibits excellent conductivity and can improve the characteristics of the battery.

The negative electrode active material for a lithium secondary battery manufactured as described above may have a shape in which carbon nanofibers are grown on the surface while maintaining a spherical shape. In this case, the negative electrode active material can realize excellent battery characteristics.

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

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

The negative electrode active material layer includes a binder, and may optionally include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride , Polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

Examples of the water-soluble binder include styrene-butadiene rubber, acrylated styrene-butadiene rubber, polyvinyl alcohol, sodium polyacrylate, propylene and olefin copolymers having 2 to 8 carbon atoms, (meth) acrylic acid and (meth) Copolymers or combinations thereof.

The conductive material is used for imparting conductivity to the electrode. Any electrically conductive material can be used without causing any chemical change. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, Carbon-based materials; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

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

The anode includes a current collector and a cathode active material layer formed on the current collector. As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. As a more specific example, a compound represented by any one of the following formulas may be used.

Li _a A _{1 - b} X _b D ₂ (0.90? A? 1.8, 0? B? 0.5); Li _a A _{1 - b} X _b O _{2 - c} D _c (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05); LiE _{1 - b} X _b O _{2 - c} D _c (0? B? 0.5, 0? C? 0.05); LiE _{2 - b} X _b O _{4 - c} D _c (0? B? 0.5, 0? C? 0.05); Li _a Ni _{1 -b- c} Co _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <?? 2); Li _a Ni _{1 -b- c} Co _b X _c O _{2 -α} T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1 -b- c} Co _b X _c O _{2 - ?} T ₂ (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? <2); Li _a Ni _{1 -b- c} Mn _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <?? 2); Li _a Ni _{1 -b- c} Mn _b X _c O _{2- α} T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1 -bc} Mn _b X _c O _2-α T ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, 0.001? D? 0.1); Li _a Ni _b Co _c Mn _d G _e O ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a CoG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a MnG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a Mn ₂ G _b O ₄ (0.90? A? 1.8, 0.001? B? 0.1); Li _a MnG _b PO ₄ (0.90? A? 1.8, 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiZO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); LiFePO ₄

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X 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 the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, 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; Z 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.

A compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise at least one coating element compound selected from the group consisting of oxides, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be any coating method as long as it can coat the above compound by a method that does not adversely affect physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

The cathode active material layer includes a binder and / or a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any electrically conductive material can be used without causing any chemical change, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, , Metal powders such as nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, aluminum may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition and applying the composition to an electric current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

In the non-aqueous liquid electrolyte secondary battery according to an embodiment of the present invention, the non-aqueous electrolyte includes a non-aqueous 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 battery can move.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / poly It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

Hereinafter, examples of the present invention will be described. The following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

Example  One

(Preparation of negative electrode active material)

(One) NCMO Production of Aggregate

Nickel, and cobalt manganese is 0.34: 0.27: 0.39. Manganese sulfate hydrate (MnSO ₄ .5H ₂ O), nickel sulfate hydrate (NiSO ₄ .6H ₂ O), and cobalt sulfate hydrate (CoSO ₄ .7H ₂ O) were used as raw materials for the metal aqueous solution, Thereby preparing an aqueous metal solution.

Sodium hydroxide (NaOH) is used as a precipitant to precipitate the precursor in the prepared metal aqueous solution. The molar ratio of the metal aqueous solution to sodium hydroxide is 1: 1.6 to 1: 2.4. Ammonia water is used as a chelating agent, and the molar ratio of the metal aqueous solution to the aqueous ammonia is 1: 0.1 to 1: 1.2. The metal aqueous solution, sodium hydroxide and ammonia water are continuously fed into the continuous reactor by using a metering pump. The stirring speed in the continuous reactor is adjusted to about 500 to 2000 rpm (about 1200 rpm) and stirring is performed. At this time, the inside of the reactor is at 50 ° C and the atmosphere is substituted with N ₂ .

After the precipitation reaction is completed by stirring the continuous reactor, the precipitated precursor is filtered and washed, and dried in an oven at 60 to 120 ° C.

The prepared _{Ni 0 .34 Co 0 .27 Mn 0} .39 (OH) 2 particles are spherical, the particle size distribution is uniform.

1 is a scanning electron micrograph of the metal hydroxide precursor Ni _{0 .34} Co _{0 .27} Mn _{0 .39} (OH) ₂ of Example 1. It can be seen from FIG. 1 that a precursor having a size of 10 μm to 20 μm was formed.

Thereafter, the metal hydroxide particles are heated at 700 캜 for 5 hours in an air atmosphere. This is the metal hydroxide is converted to _{(Ni 0 .34 Co 0 .27 Mn} 0 .39) 3 O 4 through.

(2) carbon nanofibers grown on the surface NCMO Production of base negative electrode active material

5 g of the NCMO-based active material prepared according to the above is put into an alumina crucible and then placed in a tube furnace. And heated at 600 DEG C for 1 hour to reduce a portion of the surface of the NCMO-based active material to become a metal seed.

The acetylene gas is flowed at 600 DEG C for 1.5 minutes per minute for 10 minutes to the material obtained through the reduction step. As a result, a negative electrode active material for a lithium secondary battery in which carbon nanofibers are grown on the surface of an NCMO-based active material is produced.

FIG. 2 is a scanning electron microscope (SEM) image of the negative electrode active material on which carbon nanofibers are grown.

FIG. 3 is a transmission electron micrograph of a carbon nanofiber portion taken from the negative electrode active material of Example 1. FIG. The average diameter of the carbon nanofibers grown through FIG. 3 is about 10 nm.

4 is a Fourier transform pattern of a carbon nanofiber portion in the negative electrode active material of Example 1. FIG. FIG. 4 shows that carbon nanofibers made of amorphous carbon are formed.

(Manufacture of Battery)

The negative electrode active material prepared above, a carbon black conductive material, a polyacrylic acid binder and a carboxymethylcellulose binder were prepared at a weight ratio of 6: 2: 1: 1, and the mixture was dispersed in an N-methyl-2-pyrrolidone solvent Thereby preparing an anode active material slurry.

The slurry is coated on a copper foil and dried to prepare an electrode plate.

A 2016R coin cell battery is manufactured using a lithium metal as a counter electrode plate and a mixed solution of 1.3M LiPF ₆ ethylene carbonate, ethyl methyl carbonate 3: 7 by volume and a 10% fluorethylene carbonate as an electrolyte.

Experimental Example  1: Evaluation of voltage profile

In order to evaluate the electrochemical characteristics of the negative electrode active material prepared in Example 1, the voltage profile of the battery of Example 1 was evaluated, and the results are shown in FIG. At 0.1C rate, the voltage range was measured from 0.05V to 3.0V.

In Fig. 5, the falling curve indicates the discharge capacity and the rising curve indicates the charging capacity. Referring to FIG. 5, the initial discharge capacity was 1063 mAh / g and the charge capacity was 725 mAh / g, indicating that the initial charge / discharge characteristics were excellent.

Experimental Example  2: Evaluation of life characteristics

The life characteristics of the battery prepared in Example 1 were evaluated up to the 50th cycle, and the results are shown in FIG. The voltage range from 0.05V to 3.0V was measured at 0.1C rate.

In FIG. 6, the left vertical axis represents the charging capacity and the right vertical axis represents the coulomb efficiency. Referring to FIG. 6, it can be seen that the battery of Example 1 exhibits a high capacity of 750 mAh / g even after the 50th cycle and achieves a capacity retention rate of 90% or more.

Experimental Example  3: Evaluation of high rate characteristics

The high-rate characteristics of the cells prepared in Example 1 were evaluated, and the results are shown in FIG. Referring to FIG. 7, in the case of Example 1, a capacity of 450 mAh / g can be realized even at a 10 C rate. This is probably due to the increased electrical conductivity due to the carbon nanofibers grown on the surface.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (23)

A metal oxide represented by the following formula (1), and
An anode active material for a lithium secondary battery comprising carbon nanofibers positioned on a surface of the metal oxide;
[Chemical Formula 1]
M _x O _y
In the above formula (1), M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof; x: y is 1: 0.5 to 1: 2. The method of claim 1,
Wherein the carbon nanofibers are grown on the surface of the metal oxide. The method of claim 1,
Wherein M is Ni, Mn, Co, or a combination thereof. The method of claim 1,
Wherein M is a combination of Ni, Mn, and Co in the formula (1). The method of claim 1,
The negative active material for a lithium secondary battery according to claim 1,
(2)
(Ni _a Co _b Mn _c ) _x O _y
0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1, and x: y are from 1: 0.5 to 1: 2. The method of claim 1,
Wherein the metal oxide has a particle diameter of 1 占 퐉 to 50 占 퐉. The method of claim 1,
Wherein the carbon nanofiber has a diameter of 10 nm to 70 nm. The method of claim 1,
Wherein the negative electrode active material for a lithium secondary battery is a spherical negative electrode active material for a lithium secondary battery. The method of claim 1,
Wherein the negative electrode active material for a lithium secondary battery has a particle diameter of 1 占 퐉 to 50 占 퐉. A negative electrode comprising the negative electrode active material for a lithium secondary battery according to any one of claims 1 to 9,
Anode, and
A lithium secondary battery comprising an electrolyte. Preparing a metal hydroxide of Formula 11;
Heat treating the metal hydroxide to obtain a metal oxide represented by the following formula (1); And
And supplying a carbon source to the metal oxide to form carbon nanofibers on the surface of the metal oxide. The method for producing a negative electrode active material for a lithium secondary battery according to claim 1,
(11)
M (OH) _n
In Formula 11, M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof.
[Chemical Formula 1]
M _x O _y
In the above formula (1), M is Ni, Mn, Co, Fe, Al, Mg, Zn, Ti, or a combination thereof; x: y is 1: 0.5 to 1: 2. 12. The method of claim 11,
The formula (11) is represented by the following formula (12)
Wherein the negative active material for a lithium secondary battery is represented by the following Chemical Formula 2:
[Chemical Formula 12]
Ni _a Co _b Mn _c (OH) _n
0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1,
(2)
(Ni _a Co _b Mn _c ) _x O _y
0? A? 0.85, 0? B? 0.85, 0? C? 0.85, 0.9? A + b + c? 1.1, and x: y are from 1: 0.5 to 1: 2. 12. The method of claim 11,
The step of preparing the metal hydroxide of the formula (11)
Adding a metal raw material to a solvent to prepare a metal aqueous solution,
Stirring the metal aqueous solution, and
And drying the precipitate obtained in the above step. The method of claim 13,
Wherein the precipitating agent and / or chelating agent is further added in the step of preparing the metal aqueous solution. 12. The method of claim 11,
Wherein the step of heat treating the metal hydroxide to obtain the metal oxide of Formula 1 is performed at 500 ° C to 800 ° C. 12. The method of claim 11,
Wherein the metal oxide has a particle diameter of 1 to 50 占 퐉. 12. The method of claim 11,
The method for producing a negative electrode active material for a lithium secondary battery according to the present invention comprises the steps of: after heat treating the metal hydroxide to obtain a metal oxide represented by the general formula (1)
And reducing the metal oxide to form a metal seed on a part of the surface of the metal oxide. 12. The method of claim 11,
In the step of forming a carbon nanofiber on the surface of the metal oxide by supplying a carbon source to the metal oxide,
Wherein the carbon nanofibers are grown on the surface of the metal oxide. 12. The method of claim 11,
Wherein the carbon raw material is a vapor-phase carbonaceous material. 12. The method of claim 11,
Wherein the step of supplying the carbon source to the metal oxide to form the carbon nanofiber on the surface of the metal oxide is performed at 500 ° C to 800 ° C. 12. The method of claim 11,
Wherein the diameter of the carbon nanofibers is 10 nm to 70 nm. 12. The method of claim 11,
Wherein the negative electrode active material for a lithium secondary battery is a spherical negative electrode active material for a lithium secondary battery. 12. The method of claim 11,
Wherein the obtained negative electrode active material for lithium secondary battery has a particle diameter of 1 to 50 占 퐉.

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