KR20160123078A - Anode active material, lithium secondary battery comprising the material, and method of preparing the material - Google Patents

Abstract

The present invention relates to a method for manufacturing a lithium secondary battery, comprising: mixing a (sub) metal oxide and a lithium metal powder; And a carbon precursor material is added to the mixed metalloid oxide and the lithium metal powder, and the carbon precursor material is heat-treated to alloy the metal oxide with lithium, and carbon coating the alloyed metal oxide and lithium simultaneously And a shell portion including a carbon material coated on a surface of the core portion, the core portion including a (sub) metal oxide-Li alloyed (MOx-Liy) (MOx-Liy) -C composite (where M is a (sub) metal, x is more than 0 and less than 1.5, y is more than 0 and less than 4) of a core- ≪ / RTI >

Description

[0001] The present invention relates to a negative electrode active material, a lithium secondary battery including the same, and a method for manufacturing the negative electrode active material,

The present invention relates to a negative electrode active material including a composite of a negative electrode active material, specifically a core-shell structure, a lithium secondary battery including the same, and a method for manufacturing the negative electrode active material.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices have attracted the greatest attention in this respect, among which the development of rechargeable secondary batteries has become a focus of attention. In recent years, in order to improve the capacity density and specific energy in developing such batteries, And research and development on the design of the battery.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution . However, among these lithium ion secondary batteries, there are safety problems such as ignition and explosion in using an organic electrolytic solution, and they are disadvantageous in that they are difficult to manufacture. Recently, the lithium polymer secondary battery is considered to be one of the next generation batteries by improving the weak point of such a lithium ion secondary battery. However, since the capacity of the battery is still relatively low as compared with the lithium ion secondary battery and the discharge capacity at low temperature is insufficient There is an urgent need for improvement.

For this purpose, there is a growing need for a high-capacity anode material, and a (quasi) metallic material such as a Si-based or Sn-based material having a large theoretical capacity is applied as a negative electrode active material. However, as the charging and discharging are repeatedly performed, The characteristics were deteriorated and the volume expansion was severe, which adversely affected the performance and safety of the battery. Therefore, research has been carried out to mitigate cycle characteristics and volume expansion by using (quasi-) metal oxides such as silicon oxides (SiOx), but the (quasi-) metal oxides have been found to be non- So that the initial efficiency is extremely low.

In order to compensate for this, when the (quasi-) metal oxide is pre-alloyed with the (quasi) metal oxide and lithium so as to contain lithium, irreversible phase such as lithium oxide, lithium metal oxide, The initial efficiency of the negative electrode active material can be increased.

However, lithium by-products generated in the course of the reaction between the (quasi-) metal oxide and the lithium source may remain on the surface of the composite, and as a result, the pH of the aqueous binder system including the quasi-metal oxide is increased to make it difficult to mix the slurry of the anode active material. There is a problem that the adhesive force to the electrode is weakened by changing the physical properties of the binder in the slurry.

Accordingly, an object of the present invention is to provide an anode active material having excellent cyclic characteristics and volume expansion control ability between a lithium source and a (quasi-) metal oxide while suppressing reactivity with a by- .

According to an aspect of the present invention, there is provided a method of manufacturing a lithium secondary battery, comprising: (a) firstarily alloying a (sub) metal oxide and a lithium metal powder; And a carbon precursor material is added to the primary alloyed quasi metal oxide and the lithium metal, and the carbon precursor material is heat treated to thermally treat the quasi- metal oxide and the lithium metal to form a secondary alloy of the (quasi-) metal oxide and lithium, (MO _x -L _y ), and a shell comprising a carbon material coated on the surface of the core part (a), the method comprising the steps of: (a) (MO _{x -} Li _y ) - C composite having a core-shell structure, wherein M is a (sub) metal, x is more than 0 and less than 1.5, y is more than 0 and less than 4 The present invention also provides a method for producing the negative electrode active material.

In addition, the primary alloying step, the secondary alloying, and the carbon coating step may be performed in the same rotating tubular furnace.

Also, the rotating tubular body can rotate at a speed of 5 to 20 rpm / min.

According to a preferred embodiment of the present invention, the heat treatment time may be 1 to 10 hours, and the heat treatment temperature may be 400 to 1000 ° C.

According to another embodiment of the present invention, the (quasi) metal is at least one selected from the group consisting of Si, Sn, Al, Sb, Bi, As, Ge, Pb, Zn, Cd, In, Ti, Ga, ≪ / RTI >

According to another preferred embodiment of the present invention, the (sub) metal oxide may be a single compound selected from the group consisting of SiO, SnO, and SnO ₂ , or a mixture of the two.

According to another preferred embodiment of the present invention, the diameter of the core portion may be 0.05 to 30 탆.

Further, according to another preferred embodiment of the present invention, the carbon coating may be coated by a chemical vapor deposition (CVD) method.

In addition, the carbon material of the shell portion may be 0.05 to 30% by weight based on the weight of the negative electrode active material.

According to another aspect of the present invention, there is provided a negative electrode active material produced by the method for manufacturing the negative active material.

According to still another aspect of the present invention, there is provided a negative electrode for a lithium secondary battery comprising a current collector, and a negative electrode active material layer formed on at least one side of the current collector and including the negative active material.

According to still another aspect of the present invention, there is provided a lithium secondary battery including a positive electrode, a negative electrode according to the present invention, and a separator interposed between the positive electrode and the negative electrode.

The present invention provides a negative electrode active material having a high capacity and a high initial efficiency as well as an excellent controllability of cycle characteristics and volume expansion.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is a SEM photograph of a negative electrode active material according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments, and not all of the technical ideas of the present invention are described. Therefore, various equivalents which can be substituted at the time of the present application It should be understood that variations can be made.

The method of manufacturing an anode active material according to the present invention includes the steps of: first alloying a (quasi-) metal oxide and a lithium metal powder; And a carbon precursor material is added to the primary alloyed quasi metal oxide and the lithium metal, and the carbon precursor material is heat treated to thermally treat the quasi- metal oxide and the lithium metal to form a secondary alloy of the (quasi-) metal oxide and lithium, (MO _x -L _y ), and a shell comprising a carbon material coated on the surface of the core part (a), the method comprising the steps of: (a) (MO _{x -} Li _y ) - C composite having a core-shell structure, wherein M is a (sub) metal, x is more than 0 and less than 1.5, y is more than 0 and less than 4 The negative electrode active material is produced.

When the lithium and the (quasi-) metal oxide are alloyed and the carbon coating is separately formed, irreversible phases such as lithium oxide and lithium metal oxide are less generated at the initial charging and discharging of the battery to improve the initial efficiency of the negative electrode active material. It is difficult to mix the anode active material slurry including the binder when used in an aqueous binder system due to the lithium byproducts remaining on the surface of the anode active material during the synthesis of the (quasi-) metal oxide. Further, The adhesion of the slurry is weakened.

In order to solve this problem, the present inventors have carried out a carbon coating functioning as a lithium-reaction barrier layer capable of suppressing a rapid reaction between lithium and a (quasi-) metal oxide. In particular, The carbon coating heat treatment step was carried out at the same time to minimize the crystal growth problem of the (sub) metal in the (sub) metal oxide due to the (quasi-) metal oxide and the heat treatment in the lithium alloying and carbon coating. When crystals grow, there is a problem that the capacity of the negative electrode active material decreases and the performance deteriorates. That is, a feature of the present invention is that a carbon coating is provided on the alloy of the (quasi-) metal oxide and lithium, and in particular, the heat treatment in the case of lithium alloying with the (quasi-) metal oxide does not proceed with the heat treatment in the carbon coating, (MO _x -L _y ) and a carbon coating by conducting a heat treatment.

Hereinafter, a method of manufacturing the negative electrode active material according to the present invention will be described in more detail.

The core part according to the invention comprises an oxide of a (sub) metal. The metal may be selected from the group consisting of Si, Sn, Al, Sb, Bi, As, Ge, Pb, Zn, Cd, In, Ti, Ga and alloys thereof but is not limited thereto. The (sub) metal (s) are present in the core portion in the form of oxides. Preferably, the oxide of the (quasic) metal is not limited to one kind of compound selected from the group consisting of SiO, SnO and SnO ₂ , or a mixture of the two. In order to control the content of oxygen of the (sub) metal oxide of the final product, it may further comprise a (sub) metal such as the above-mentioned (sub) metal.

In addition, the lithium metal powder and the (quasi-) metal oxide can be uniformly mixed using a mechanical mixing method. Here, the mechanical mixing is to apply a mechanical force to crush and mix materials to be mixed to form a uniform mixture.

In addition, the lithium metal powder and the (quasi-) metal oxide can be simply and dryly mixed, in which case the mixing equipment can be used without limitation as long as it is commonly known in the art. For example, a shaker, a stirrer, or the like may be used.

The (sub) metal oxide and the lithium metal powder are mixed so that the weight ratio is about 70:30 to about 98: 2. This mixing ratio is a set value because lithium is a very light metal, and it is difficult to mix it in excess of the above-mentioned weight ratio in comparison with the (sub) metal oxide.

When the weight ratio of the lithium metal powder is less than 2, the content of lithium in the final product is too small and the initial efficiency is not so high. On the other hand, when the weight ratio of the lithium metal powder is more than 30, lithium oxide or lithium silicate, which is inactive phases, is excessively produced in the final product, and the discharge capacity per unit weight is reduced. The metal part can cause an alloying reaction with lithium. Such lithium oxide or lithium silicate is a relatively stable phase, but a lithium- (quasi-) metal compound such as a Li-Si compound becomes unstable when left outside. For example, when about 10% by weight of the lithium metal powder is mixed with the (sub) metal oxide, the initial efficiency may reach about 90%.

Thereafter, through the heat treatment, not only the alloying of the (quasi-) metal oxide and the lithium but also the carbon coating proceeds simultaneously. When the mixture is heat-treated in an inert atmosphere in the reactor, the (quasi-) metal oxide and lithium react with each other to form new bonds, wherein lithium may exist in the form of lithium oxide or lithium (quasi) metal oxide. At the same time, the carbon precursor is carbonized by heat treatment for coating with the carbon precursor. According to one more specific embodiment, a deposition method such as a chemical vapor deposition (CVD) method using a gas including carbon such as methane, ethane, propane, ethylene, acetylene and the like can be used and is not limited thereto. Examples of the amorphous carbon precursor include resins such as phenol resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide resin, furan resin, cellulose resin, epoxy resin and polystyrene resin, coal type pitch, (tar) or a low molecular weight heavy oil.

In addition, the carbon material may be used in an amount of about 0.05 to about 30% by weight, or about 1 to about 20% by weight based on the weight of the negative electrode active material

In this case, the heat treatment temperature range is preferably 400 to 1000 占 폚, preferably 500 to 900 占 폚, more preferably 600 to 900 占 폚, in the range of the melting point to the boiling point temperature of the lithium metal powder.

If the boiling point of the lithium metal powder is exceeded, the reaction between the lithium metal powder and the (quasi-) metal oxide may not occur. If the boiling point of the lithium metal powder is exceeded, The powder can be evaporated in the form of a gas. On the other hand, if the temperature is higher than 1000 ° C, there is a high possibility that problems such as growth of Si peak due to improvement in crystallinity of the (quasi-) metal oxide may occur. Further, if it is lower than 400 ° C, it can not exist in the form of a lithium- (sub) metal oxide.

The heat treatment time is preferably 1 to 10 hours, preferably 2 to 7 hours, more preferably 2 to 5 hours. Particularly, when the heat treatment time is longer than 10 hours, the possibility of occurrence of problems such as growth of Si peak due to improvement of crystallinity of the (quasi-) metal oxide is increased. In addition, if it is shorter than 1 hour, sufficient lithium silicate is not formed and initial initial efficiency may not increase as expected.

The heat treatment is preferably performed in an inert gas atmosphere in which nitrogen gas, argon gas, helium gas, krypton gas, or xenon gas is present in order to block contact with oxygen. If the mixture comes into contact with oxygen at the time of heat treatment of the mixture, the lithium source and oxygen react with the metal oxide together to form lithium oxide or lithium metal oxide, so that the initial efficiency increase effect of the battery can be reduced.

In this (sub) metal oxide-Li alloy, the oxygen content of the (sub) metal oxide is MO _x (0 <x <1.5) ) Is relatively small, which may cause a reduction in the total energy density, and may also cause a problem of lowering the initial efficiency.

Through such a manufacturing method, it is possible to provide a method of manufacturing a semiconductor device, which comprises a core portion including (quasi-) metal oxide-Li alloys (MO _x -L _y ) and a shell portion including a carbon material coated on the surface of the core portion (MO _x -Li _y ) -C composite (where M is a (sub) metal, x is more than 0 and less than 1.5, and y is less than 4 but less than 4) in a core- .

The core portion may have a diameter of about 0.05 to about 30 탆, or about 0.5 to about 15 탆.

When the carbon coating is not performed, the reaction between the lithium metal powder, for example, lithium and the (sub) metal oxide of the lithium metal powder is not controlled, and the metal crystal phase in the (sub) metal oxide is rapidly grown. The growth of such a metal crystal phase may cause stress to occur due to the volume expansion due to the weak ionic bond between the metal and the lithium, so that cracks may easily occur. Such cracks may occur irregularly, which may result in a portion of the material not contacting the electrolyte or an electrically isolated portion, which may lead to a failure of the battery.

The thus-prepared negative electrode active material of the present invention can be manufactured into a negative electrode according to a manufacturing method commonly used in the art.

For example, the electrode active material of the present invention can be prepared by mixing and stirring a binder and a solvent, if necessary, with a conductive material and a dispersing agent to prepare a slurry, applying the slurry to a current collector, and compressing the electrode. In particular, the negative electrode active material according to the present invention solves the problem that the pH is increased, which may be caused by Li by-products in an aqueous binder containing water as a dispersion medium. Also, the anode according to the present invention can be produced by a conventional method in the art, like the cathode.

As the binder, polyvinylidene fluoride-co-hexafluoro propylene (PVDF-co-HFP), polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride- Polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate (also referred to as polyvinylpyrrolidone), polyvinylpyrrolidone polyvinyl acetate, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate ), Cyanoethylpullulan, cyanoethyl But are not limited to, cyanoethylpolyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose (CMC), acrylonitrile-styrene-butadiene But are not limited to, those selected from the group consisting of acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinylidenefluoride, polyacrylonitrile, and styrene butadiene rubber (SBR) Or a mixture of two or more thereof.

As the cathode active material, a lithium-containing transition metal oxide may be preferably used. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO _{2 x <1.3), Li x Mn} 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, Li _x Co _{1 - y} Mn _y O ₂ (where 0 <c <1, a + b + c = 1), Li _x Ni _1-y Co _y O ₂ 0.5 <x <1.3, 0≤y < 1), Li x Ni 1 -y Mn y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn c) O 4 ( 0.5 <x <1.3, 0 < a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li x Mn 2 - z Ni z O 4 (0.5 <x <1.3, 0 <z <2), Li x Mn 2 - z Co z O 4 (0.5 <x <1.3, 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) and Li _x FePO ₄ (0.5 < x < 1.3), or a mixture of two or more thereof. The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

When the electrode is manufactured, a lithium secondary battery having a separator and an electrolyte interposed between the positive electrode and the negative electrode, which is conventionally used in the art, can be manufactured using the electrode.

In the electrolyte used in the present invention, the lithium salt that may be included as the electrolyte may be any of those conventionally used in an electrolyte for a lithium secondary battery. For example, examples of the anion of the lithium salt include F ^- , Cl ^- , Br ^{- _{, I -, NO 3 -,}} N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 _{^{PF 2 -, (CF 3)}} 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N _{^{-, CF 3 CF 2 (CF}} 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

As the organic solvent contained in the electrolytic solution used in the present invention, the organic solvent commonly used in the electrolyte for a lithium secondary battery can be used without limitation, and examples thereof include propylene carbonate (PC), ethylene carbonate (ethylene carbonate) EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxy But are not limited to, ethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, fluoro-ethylene carbonate (FEC) and propionate esters such as methyl- Methyl-propionate, ethyl-propionate, propyl-propylate, Carbonate (propyl-propionate), Butyl-like propionate (butyl-propionate) or any mixture of two or more of those selected from the group consisting of the like can be used as a representative. In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high-viscosity organic solvent and dissociate the lithium salt in the electrolyte well. To such a cyclic carbonate, dimethyl carbonate and diethyl When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

Alternatively, the electrolytic solution stored in accordance with the present invention may further include an additive such as an overcharge inhibitor or the like contained in an ordinary electrolytic solution.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, a polyolefin such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer A porous polymer film made of a high molecular weight polymer may be used alone or in a laminated manner, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, a polyethylene terephthalate fiber or the like may be used. It is not.

Optionally, the separator may further comprise a porous coating layer on its surface. The porous coating layer includes inorganic particles and a binder. The binder is located on a part or all of the inorganic particles, and functions to connect and fix the inorganic particles.

The inorganic particles may be inorganic particles having a dielectric constant of about 5 or more, or inorganic particles having a lithium ion transporting ability (in the case of a lithium secondary battery), either singly or in combination. The inorganic particles having a dielectric constant of about 5 or more are BaTiO ₃ , Pb (Zr _x , Ti _1-x ) O ₃ (PZT, 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, 0 <x <1 , 0 <y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -x PbTiO 3 (PMN-PT, 0 <x <1), Wherein the metal oxide selected from the group consisting of hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ Or a mixture of two or more thereof. The inorganic particles having lithium ion transferring ability include, but are not limited to, lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x < lithium aluminum titanium phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2, 0 <y <1, 0 <z <3) (LiAlTiP) x O y series glass (glass), (0 < x <4, 0 <y < 13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2,0 <y <3), lithium germanium thiophosphate Mani Titanium (Li _x Ge _y P _z S _{w, 0 <x <4,} 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS _{2 (Li x Si y S z} , 0 <x <3,0 <y <2,0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 < y <3, 0 <z <7) series glass, or a mixture of two or more thereof. The average particle size of the inorganic particles is not particularly limited, but may range from about 0.001 탆 to about 10 탆 for the formation of a porous coating layer of uniform thickness and proper porosity. When the average particle diameter of the inorganic particles satisfies the above range, the dispersibility of the inorganic particles can be prevented from decreasing, and the porous coating layer can be adjusted to an appropriate thickness.

The binder may be included in an amount of about 0.1 to about 20 parts by weight, preferably about 1 to about 5 parts by weight, based on 100 parts by weight of the total amount of the binder and the inorganic particles. Non-limiting examples thereof include polyvinylidene fluoride-co-hexafluoro propylene (PVDF-co-HFP), polyvinylidene fluoride-co-trichloroethylene Polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, poly (vinylpyrrolidone), polyvinylpyrrolidone, But are not limited to, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate cellulose acetate propionate, cyanoethylpullulan, But are not limited to, polyvinylpyrrolidone, polyvinyl alcohol, cyanoethylpolyvinylalcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose (CMC), acrylonitrile-styrene Acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinylidene fluoride, polyacrylonitrile, and styrene butadiene rubber (SBR). Any one selected or a mixture of two or more thereof.

The battery case used in the present invention may be of any type that is commonly used in the art, and is not limited in its external shape depending on the use of the battery. For example, a cylindrical case, a square type, a pouch type, (coin) type or the like.

Hereinafter, embodiments of the present invention will be described in detail to facilitate understanding of the present invention. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Example

10 g of SiO 2 having an average particle size of 5 탆 as a (sub) metal oxide was mixed with a lithium metal powder in a weight ratio of 92: 8, and the mixture was introduced into a rotating tubular furnace. While rotating the rotating tubular furnace at a rate of 10 rpm / And then heat-treated at 500 ° C for 2 hours to first alloy lithium to the core portion. Thereafter, the temperature was raised to 900 DEG C at a rate of 5 DEG C / minute while introducing argon gas into the same rotating tubular furnace at 1.0 L / min. The secondary tubular alloying of the core was performed by rotating the rotating tubular furnace at a rate of 10 rpm / min while flowing argon gas at 1.8 L / min and acetylene gas at 0.3 L / min for 3 hours, At the same time, a surface carbon coating was performed to prepare a (MOx-Liy) -C composite anode active material having a core-shell structure. Here, the carbon content of the carbon coating layer was 10 parts by weight based on 100 parts by weight of the core portion.

1 is a SEM photograph of a negative electrode active material according to an embodiment of the present invention.

Comparative Example

The anode active material was prepared by separately performing lithium alloying and surface carbon coating using a horizontal tubular furnace and a vertical tubular furnace in a different manner from the rotary tubular furnace in the above embodiment. (Quasi) metal oxide was mixed in a weight ratio of 92: 8 of lithium metal powder to form a mixture. The mixture was charged into a horizontal tubular furnace and subjected to heat treatment at 700 ° C for 5 hours in an Ar atmosphere to alloy the core with lithium. Further, the material obtained above was charged into a vertical tubular furnace, and the temperature was raised to 900 DEG C at a rate of 5 DEG C / min while introducing argon gas at 1.0 L / min. Thereafter, carbon coating was performed by flowing argon gas at 1.8 L / min and acetylene gas at 0.3 L / min for 3 hours to prepare a (MOx-Liy) -C composite anode active material having a core-shell structure.

Test Example

The anode active material prepared in the above Examples and Comparative Examples and graphite were mixed at a weight ratio of 15:85. Then, carbon black and SBR / CMC were mixed as a conductive agent in a weight ratio of 94: 2: 2: 2. These were mixed in distilled water as a solvent and mixed to prepare a uniform electrode slurry.

Experiment result

Unlike the comparative examples in which the lithium alloying and the carbon coating are separately performed, the embodiments can perform the lithium alloying and the carbon coating in a series of processes, thereby shortening the manufacturing time of the negative electrode active material and more uniformly alloying and carbon coating .

Claims (13)

A step of first alloying a (quasi-) metal oxide and a lithium metal powder; And a carbon precursor material is added to the primary alloyed quasi metal oxide and the lithium metal, and the carbon precursor material is heat treated to thermally treat the quasi- metal oxide and the lithium metal to form a secondary alloy of the (quasi-) metal oxide and lithium, And a heat treatment step for causing the heat treatment to proceed simultaneously,
A core-shell having a core including a quasi-metal oxide-Li alloyed MOx-Liy and a shell including a carbon material coated on a surface of the core, (Wherein M is a (sub) metal, x is more than 0 and less than 1.5, and y is less than 4 but less than 4) in the structure of (MOx-Liy) -C. The method according to claim 1,
Wherein the primary alloying step, the secondary alloying step, and the carbon coating step are performed in the same rotary tubular furnace. 3. The method of claim 2,
Wherein the rotating tubular body is rotated at a speed of 5 to 20 rpm / min. The method according to claim 1,
Wherein the heat treatment time is 1 to 10 hours. The method according to claim 1,
Wherein the heat treatment temperature is 400 to 1000 占 폚. The method according to claim 1,
Wherein the (quasi) metal is selected from the group consisting of Si, Sn, Al, Sb, Bi, As, Ge, Pb, Zn, Cd, In, Ti, Ga and alloys thereof. The method according to claim 1,
Wherein the (quasi-) metal oxide is one kind of compound selected from the group consisting of SiO, SnO, and SnO ₂ , or a mixture of two kinds. The method according to claim 1,
And the core portion has a diameter of 0.05 to 30 占 퐉. The method according to claim 1,
Wherein the carbon coating is coated by a chemical vapor deposition (CVD) method. The method according to claim 1,
Wherein the carbon material of the shell portion is 0.05 to 30% by weight based on the weight of the negative electrode active material. A negative electrode active material produced by the method for producing a negative electrode active material according to any one of claims 1 to 10. And a negative electrode active material layer formed on at least one side of the current collector and including the negative electrode active material of claim 19. 12. A lithium secondary battery comprising a positive electrode, a negative electrode according to claim 12, and a separator interposed between the positive electrode and the negative electrode.

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