KR101722960B1 - Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

The present invention relates to an M-Si composite body gymnastic method used as an anode active material of a lithium secondary battery by forming a structural support of porous silica including silicon (Si) and metal (M) through a process step and an etching step, followed by an oxidation step And provides a lithium secondary battery having a stable cyclic characteristic with a small capacity reduction due to an increase in cycle.

Description

TECHNICAL FIELD The present invention relates to a negative active material for a lithium secondary battery, a method for producing the negative active material, and a lithium secondary battery including the same. [0001] The present invention relates to a negative active material for a lithium secondary battery,

A negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same.

Cells generate electricity by using materials that can electrochemically react to the positive and negative electrodes. A representative example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when the lithium ions are intercalated / deintercalated in the positive electrode and the negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

As the cathode active material of the lithium secondary battery, a lithium composite metal compound is used. Examples of the lithium composite metal compound include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x O ₂ (0 <x <1), LiMnO ₂ Metal oxides are being studied.

As the negative electrode active material of the lithium secondary battery, graphite capable of inserting / removing lithium has been typically used. However, since such a graphite electrode has a low charge capacity of 365 mAh / g (theoretical value: 372 mAh / g), there is a limit in providing a lithium secondary battery exhibiting excellent capacity characteristics.

Accordingly, inorganic active materials such as silicon (Si), germanium (Ge), and antimony (Sb) have been studied. The inorganic active material, particularly, the silicon anode active material has an advantage of realizing a high capacity (3650 mAh / g) when it reacts with lithium ion at room temperature.

However, in the inorganic negative electrode active material such as silicon, when the insertion / removal of lithium, that is, the charge / discharge of the battery is changed by 300% or more, contact between the current collector and the active material becomes weak. In addition, since the electric conductivity of silicon is low, a charge transfer reaction that occurs when lithium is intercalated / deintercalated does not occur smoothly. For this reason, the previously known inorganic anode active material, for example, a silicon anode active material and a lithium secondary battery including the lithium anode active material have disadvantages in that they exhibit a low cycle life characteristic and a capacity retention ratio despite their advantages according to their high charge capacities.

The present invention relates to a porous M-Si composite having a metal oxide core at its center to provide an M-Si composite used as an anode active material of a lithium secondary battery having a stable cycle characteristic with little reduction in capacity due to an increase in cycle, .

In one embodiment of the present invention, a first M-Si composite preparation step comprising silicon (Si) and metal (M) in a weight ratio of 1:14 to 1: 4; (M) of the first M-Si composite is etched so that a porosity (P1) by the metal etching on the surface of the first M-Si composite is greater than a porosity An etching step of obtaining a second M-Si composite having a porosity (P2) higher than that of the first M-Si composite; And oxidizing a part or the whole of the metal (M) in the second M-Si composite to obtain a third M-Si composite. The present invention also provides a method for producing an M-Si composite for a lithium secondary battery anode active material do.

Also, the first M-Si composite preparation step may include mixing at least one metal (M) powder selected from the group consisting of Al, Cu, Ni, and Zn to mix the silicon (Si) powder and the metal (M) And then slowly cooling the resultant mixture to prepare a first M-Si composite. The present invention also provides a method for producing an M-Si composite for a lithium secondary battery anode active material.

The etching step may further include etching the metal (M) of the first M-Si composite at a temperature of 5 ° C to 25 ° C for 10 minutes to 60 minutes using an etchant. The M-Si composite for a lithium secondary battery anode active material Of the present invention.

The etching solution is phosphoric acid (H ₃ PO _4), nitric acid (HNO _3), acetic acid (CH ₃ COOH), hydrochloric acid (HCl), sulfuric acid (H ₂ SO _4), J. ferric chloride (Fe ₂ Cl), aqueous ammonia (NH ₄ OH ), Hydrogen peroxide (H ₂ O ₂ ), and hydrogen fluoride (HF).

Wherein the oxidation step is performed for 10 to 30 minutes at a temperature of 740 to 760 캜 under oxygen (O ₂ ) and water vapor (H ₂ O), and the _second M- Si composite according to the present invention.

A first coating step of coating carbon on the surface of the third M-Si composite after the oxidation step, and a second coating step of coating SiOx (0 < x &lt; 2) on the third M-Si composite The present invention also provides a method for producing an M-Si composite for an anode active material of a lithium secondary battery.

In an embodiment of another aspect of the present invention, there is provided an M-Si composite including silicon (Si) and a metal (including a metal oxide), wherein the porosity (P1) higher than the porosity (P2) in composite center, some or all of the metal (M) is a metal oxide (M _x O _y), wherein the metal oxide (M _x O _y) is 20% to 60 by weight of M-Si % By weight based on the total weight of the negative electrode active material.

Wherein the metal (M) is at least one selected from the group consisting of Al, Cu, Ni and Zn, and the average particle diameter of the M-Si composite is 10 to 12 m. .

The M-Si composite further comprises a carbon coating layer and a SiO _x (0 < _x &lt; 2) coating layer on at least a part of an outer surface of the M-Si composite for an anode active material of a lithium secondary battery.

According to an embodiment of the present invention, an M-Si composite having porous and metal oxide cores can be provided through the method for manufacturing an anode active material for a silicon-based lithium secondary battery.

In addition, the M-Si composite according to an embodiment of the present invention has excellent cycle characteristics, in which the metal exists mostly in the form of a metal oxide to form a more stable structure support and hardly causes a decrease in capacity even after charging / discharging several hundred times.

In addition, since the metal is present in the center of the M-Si composite in the form of oxide, the M-Si composite serves as a structural support and has a higher capacity than the conventional carbon-based (372 mAh / g) , Cycle characteristics and capacity retention ratios, which are excellent in lifetime characteristics.

Also, the M-Si composite according to an embodiment of the present invention may further include a carbon coating layer to effectively prevent or alleviate the microfibrillation of the M-Si composite even if the volume of the M- , And the side reactions with the electrolyte are reduced to reduce the formation of non-conductive SEI (solid-electrolyte interface). As a result, the amount of lithium that is irreversibly consumed by the SEI formation can be reduced to effectively improve the Coulomb efficiency and effectively improve the lifetime characteristics.

The M-Si composite according to an embodiment of the present invention further includes a SiO _x (0 < x? 2) coating layer to form a hard thin coating film on the M-Si composite surface, The volume expansion can be alleviated. Further, the outermost surface of the active material can be fixed, and the specific surface area can be effectively controlled.

FIG. 1 is a SEM photograph of a porous Si having a metal removed by etching according to an embodiment of the present invention.
FIG. 2 shows XRD data obtained by analyzing components in an M-Si composite according to an oxidation temperature according to an embodiment of the present invention.
FIG. 3 shows XRD data obtained by analyzing components in an M-Si composite according to an oxidation time according to an embodiment of the present invention.
4 is a graph showing charge-discharge characteristics of a half-cell manufactured according to an embodiment of the present invention.
FIG. 5 is a graph illustrating a discharge capacity measured in accordance with an increase in a cycle of 100 cycles of a half cell manufactured according to an embodiment of the present invention.
FIG. 6 is a graph illustrating a discharge capacity of a half-cell manufactured according to an embodiment of the present invention in accordance with an increase in the cycle of 300 cycles.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

The present invention provides a method for producing an M-Si composite for a lithium secondary battery anode active material. A method of manufacturing an M-Si composite for an anode active material of a lithium secondary battery according to an embodiment of the present invention includes preparing a first M-Si composite including silicon (Si) and metal (M) , An etching step to obtain a second M-Si composite with pores, and an oxidation step to oxidize the second M-Si composite to obtain a third M-Si composite having a metal oxide (M _x O _y ) core.

In preparing the first M-Si composite, a first M-Si composite is prepared through an eutectic reaction in which silicon (Si) powder and metal (M) powder, which are precursors, are mixed and melted and then slowly cooled. The cooling rate is preferably 4 to 6 占 폚 / min. More preferably 5 [deg.] C / min.

The first M-Si composite preparation step is a step of preparing the first M-Si composite by mixing and melting the silicon (Si) powder and the metal (M) powder, followed by gradual cooling to form silicon (Si) and metal (M) in a weight ratio of 1:14 to 1: A first M-Si composite is prepared. That is, 4 to 20 parts by weight of silicon (Si) relative to 100 parts by weight of the first M-Si composite. If the amount is more than 20 parts by weight, there is a problem that the battery performance is drastically lowered due to the volume expansion of the silicon-based negative electrode active material. When the weight ratio is satisfied, an M-Si composite for an anode active material of a lithium secondary battery having a high capacity per unit mass, excellent cycle characteristics, and excellent electrical conductivity can be produced by containing an appropriate amount of another metal.

Preferably, the silicon (Si) powder and the metal (M) powder are mixed in a weight ratio of 1:14 to 1: 6.7. That is, 4 to 13 parts by weight of silicon (Si) relative to 100 parts by weight of the first M-Si composite. More preferably, 12 parts by weight of silicon (Si) is contained relative to 100 parts by weight of the first M-Si composite.

The metal (M) is at least one metal selected from the group consisting of alkali metals, alkaline earth metals, transition metals, transition metals, quasi metals and combinations thereof, Is used. It is preferable to use Al which is easy to be etched because of its good reactivity.

The average particle diameter of the first M-Si composite is 10 to 12 占 퐉. This can be obtained by mixing and melting a silicon powder having an average particle diameter of 50 탆 and a metal powder having an average particle diameter of 100 탆 and adjusting the cooling conditions.

In the etching step, when the M-Si composite according to the present invention is used as a negative electrode active material of a lithium secondary battery, the volume expansion of the negative electrode material is efficiently controlled by generating a space for absorbing the volume expansion of the silicon, It is possible to prevent the cycle life of the battery from decreasing.

The etching step is a step of etching the metal (M) in the first M-Si composite to obtain a second M-Si composite in which pores are formed, and etching under a predetermined condition using an etching solution. The porosity (P1) due to the metal etching at the surface of the second M-Si composite is less than the porosity (P2) due to the metal etching at the center of the second M-Si composite since the surface is etched from the surface of the first M- high. Here, the porosity (P) means the ratio of the volume of pores in the total volume of the porous body. Therefore, the pores formed by etching the metal have a distribution decreasing from the surface of the second M-Si composite toward the center.

The etching step is carried out at a temperature below room temperature. The exothermic reaction occurs explosively when the metal reacts in the etching solution, and more specifically, it is preferably performed at a temperature of 5 to 25 ° C.

If it is etched at this temperature, it may remove a certain amount of metal contained in the first M-Si composite before etching and prevent silicon from being removed. FIG. 1 is a SEM photograph of Si having a porous structure by removing a metal by etching.

The etching step is also performed for 10 to 60 minutes. If less than 10 minutes, there is a large amount of residual metal, and since the capacity of the metal is not realized during charging and discharging of the battery, there is a problem that the capacity is reduced by an amount exceeding a certain amount of metal. There is a problem that it is hardly left.

When etching is performed for 10 to 60 minutes, the metal (M) in the second M-Si composite is included in an amount of 5 to 30 parts by weight based on 100 parts by weight of the entire second M-Si composite, Density increases. It is more preferable that the metal (M) is etched for 30 to 60 minutes to contain 10 to 20 parts by weight with respect to 100 parts by weight of the second M-Si composite.

The etching solution is phosphoric acid (H ₃ PO _4), nitric acid (HNO _3), acetic acid (CH ₃ COOH), hydrochloric acid (HCl), sulfuric acid (H ₂ SO _4), J. ferric chloride (Fe ₂ Cl), aqueous ammonia (NH ₄ OH) , Hydrogen peroxide (H ₂ O ₂ ), hydrogen fluoride (HF), and the like.

For example, the etching solution may be prepared by adding 0 to 85 parts by weight of phosphoric acid (H ₃ PO ₄ ), 0 to 70 parts by weight of nitric acid (HNO ₃ ), 0 to 30 parts by weight of acetic acid (CH ₃ COOH) 0 to 90 parts by weight of hydrochloric acid (HCl), 0 to 50 parts by weight of sulfuric acid (H ₂ SO ₄ ), 0 to 70 parts by weight of ferric chloride (Fe ₂ Cl), 0 to 90 parts by weight of ammonia water (NH ₄ OH) 0 to 90 parts by weight of hydrogen fluoride (H ₂ O ₂ ), and 0 to 30 parts by weight of hydrogen fluoride (HF).

And may further include a washing step and a drying step to remove the reaction product and the remaining etching solution after the etching step. For example, the cleaning step may be performed by dipping the second M-Si complex in a solution comprising water, an aqueous nitric acid solution, water, alcohol, acetone, or a combination thereof. The washing step may be performed one or more times while changing the washing solution, and in the case of washing a plurality of times, filtering and drying may be performed between washing steps. The drying step can also be carried out under vacuum, at a temperature of from about 80 째 C to about 150 째 C, but is not limited thereto.

The oxidation step is a step of oxidizing part or all of the metal in the second M-Si composite to obtain a third M-Si composite having a metal oxide (M _x O _y ) core. Since a certain amount of metal in the first M-Si composite is removed from the surface through the etching step, most of the metal is concentrated at the center of the second M-Si composite, and the metal is selectively oxidized through temperature control to form the metal oxide M _x O _y ) cores.

The oxidation step oxidizes only the metal (M) except for the silicon (Si) in the second M-Si composite to form a metal oxide (M _x O _y ) core. Some metals may be oxidized, some as metals, and some as metal oxides. More preferably, the structure in which most of the metal (M) is oxidized so that the metal is hardly present in the third M-Si composite and the metal oxide occupies most of the structure is more stable.

The oxidation step utilizes wet oxidation which oxidizes under oxygen (O ₂ ) and water vapor (H ₂ O).

The oxidation step is also carried out at a temperature of 740 to 760 ° C. If less than 740 ℃ and do not have sufficient oxidation problems occur, when the metal, as well as more than 760 ℃, silicon is also oxidized with, there is a problem that can not be used as the negative electrode active material of the lithium secondary battery to form the SiO _2. More preferably 750 ° C.

The oxidation step is also carried out for 10 to 30 minutes. When oxidized for 10 to 30 minutes, most of the metal can be oxidized while minimizing the oxidation of Si. More preferably 10 minutes.

The metal oxide (M _x O _y ) is contained in 20 to 60% of the weight of the third M-Si composite. Since the metal oxide is present in the center of the third M-Si composite, By using the composite as an anode active material, it is possible to provide a lithium secondary battery excellent in cycle characteristics.

After the oxidation step, the M-Si composite powder may be obtained including the washing step and the drying step of the third M-Si composite. For example, the cleaning step may be performed by dipping the second M-Si complex in a solution comprising water, an aqueous nitric acid solution, water, alcohol, acetone, or a combination thereof. The washing step may be performed one or more times while changing the washing solution, and in the case of washing a plurality of times, filtering and drying may be performed between washing steps. The drying step can also be carried out under vacuum, at a temperature of from about 80 째 C to about 150 째 C, but is not limited thereto.

The average particle size of the M-Si composite prepared by one embodiment of the present invention is preferably 10 to 12 um, more preferably 11.78 占 퐉.

The method for manufacturing an anode active material for a lithium secondary battery according to another embodiment of the present invention further includes a first coating step of coating carbon on the third M-Si composite powder to improve the capacity and cycle characteristics of the lithium secondary battery can do.

For example, the carbon coating step can be carried out by flowing hydrocarbon gas in a high temperature and inert atmosphere or in a vacuum atmosphere. As the hydrocarbon gas, acetylene gas, ethylene gas or a combination thereof may be used. In the inert atmosphere, an argon atmosphere may be used, and the high temperature may mean a temperature of about 400 ° C to about 900 ° C. However, the step of coating with carbon is not limited to this, and can be carried out using other methods and other materials.

For example, the carbon source may include sucrose, glucose, polyacrylonitrile, polyvinyl alcohol, polyvinyl pyrrolidone, colloidal carbon, (For example, by using carbonic acid, citric acid, tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine or a combination thereof) Carbon coating may be performed according to a carbonization method, a spray pyrolysis method, a layer by layer assembly method, a dip coating method, or a combination thereof.

The content of carbon in the carbon-coated third M-Si composite powder may be 1 to 50 parts by weight, more preferably 10 to 25 parts by weight, based on 100 parts by weight of the third M-Si composite. When the carbon content in the carbon-coated third M-Si composite powder is within the above range, even if the volume of the carbon-coated third M-Si composite powder is changed by insertion and desorption of lithium, the carbon-coated third M- It is possible to effectively prevent or alleviate the undifferentiation of the composite powder and reduce the side reaction with the electrolyte, thereby reducing non-conductive solid-electrolyte interface (SEI) formation. As a result, the amount of lithium that is irreversibly consumed by the SEI formation can be reduced to effectively improve the Coulomb efficiency and effectively improve the lifetime characteristics.

The method of manufacturing an anode active material for a lithium secondary battery according to an embodiment may further include a second coating step of coating SiOx (0 < x? 2) on a third M-Si composite powder.

By coating the third M-Si composite powder with SiOx (0 < x &lt; = 2), a solid thin coating film is formed on the powder surface so that the volume expansion direction of silicon is directed toward the active material center portion, . Further, the outermost surface of the active material can be fixed, and the specific surface area can be effectively controlled.

The content of SiOx (0 < x? 2) in the third M-Si composite powder coated with SiOx (0 <x? 2) is 0.001 to 10 parts by weight, May be 0.1 to 8 parts by weight. When the content of SiOx (0 <x? 2) is within the above range, the thickness of the SiOx (0 <x? 2) coating film may be 1 nm to 100 nm. In this case, the volume expansion direction of the silicon can be directed toward the center of the active material, thereby relaxing the volume expansion and controlling the specific surface area.

Meanwhile, the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment may further include coating carbon on the third M-Si composite powder coated with SiOx (0 <x? 2). The step of coating the carbon is as described above.

In another aspect of the present invention, there is provided an anode active material for a lithium secondary battery produced by the method for manufacturing a negative active material of the present invention.

The negative electrode active material for a lithium secondary battery according to an embodiment of the present invention is a material capable of reversibly intercalating / deintercalating lithium ions, and includes an M-Si composite prepared according to the negative active material manufacturing method of the present invention.

The M-Si composites according to an embodiment of the present invention include silicon (Si) and metals (including metal oxides). In the M-Si composite, the porosity (P1) on the surface of the M-Si composite is higher than the porosity (P2) in the center of the M-Si composite. Here, the porosity (P) means the ratio of the volume of pores in the total volume of the porous body.

Metal (M), some or all of the metal oxide (M _x O _y), and metal oxide (M _x O _y) of is contained in 20% to 60% by weight of M-Si composite material present in the central portion of M-Si composite do.

Since the metal oxide core serves as a more stable structure support, the M-Si composite according to one embodiment of the present invention can be used as a negative electrode active material for a lithium secondary battery having excellent cycle characteristics with almost no capacity drop even during charge / have.

The average particle size of the M-Si composite according to an exemplary embodiment of the present invention is preferably 10 to 12 um, more preferably 11.78 占 퐉.

Further, the M-Si composite according to another embodiment of the present invention may further include a carbon coating layer or SiOx (0 < x? 2) coating layer on at least a part of the outer surface.

When the carbon coating layer is further included, it contains 1 to 50 parts by weight, more preferably 10 to 25 parts by weight, of carbon with respect to 100 parts by weight of the M-Si composite. When the carbon content is within the above range, pulverization of the M-Si composite can be effectively prevented or alleviated even when the volume of the M-Si composite coated with carbon is changed by insertion and desorption of lithium, and the side reaction with the electrolyte is reduced Can reduce non-conductive solid-electrolyte interface (SEI) formation. As a result, the amount of lithium that is irreversibly consumed by the SEI formation can be reduced to effectively improve the Coulomb efficiency and effectively improve the lifetime characteristics.

In the case of further including a SiO x (0 < x? 2) coating layer, 0.001 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, based on 100 parts by weight of the M-Si composite is included. When the content of SiOx (0 <x? 2) is within the above range, the thickness of the SiOx (0 <x? 2) coating film may be 1 nm to 100 nm. In this case, since the hard thin coating film is formed on the surface of the M-Si composite, volume expansion of the silicon is directed toward the center of the active material, thereby alleviating the volume expansion. Further, the outermost surface of the active material can be fixed, and the specific surface area can be effectively controlled.

The present invention uses a porous M-Si composite having a metal oxide (M _x O _y ) core as a negative electrode active material and has a higher capacity than conventional carbon-based (372 mAh / g) commercial products, Thereby providing a lithium secondary battery excellent in characteristics.

In another aspect of the present invention, there is provided a lithium secondary battery comprising a negative electrode including a negative electrode active material for a lithium secondary battery, a positive electrode including the positive electrode active material, and an electrolyte. The lithium secondary battery according to an embodiment of the present invention may further include a separator between the anode and the cathode.

The lithium secondary battery may be a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and the electrolyte used. The lithium secondary battery may be cylindrical, square, coin or pouch type. It may be a thin film type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

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

Example

Example 1

3 g of phosphoric acid, 3 wt% of nitric acid, 3 wt% of acetic acid and 21 wt% of distilled water were added to 3 g of an Al-Si crystal composite (Al _y Si _z , 80? _Y? 90, 10? _Z? Was added to the mixed etching solution, and then stirred at room temperature for 30 minutes to prepare a porous first Al-Si composite in which a predetermined amount of aluminum (Al) was removed. Thereafter, the first Al-Si composite was washed three times using an excessive amount of water, and then dried in an oven at 80 캜.

An Al-Si composite material of claim 1 in an oxygen and water vapor at 750 ℃ for 10 minutes by a wet oxidation an alumina (Al ₂ O ₃₎ to obtain a Si-Al composite of claim 2 having a core.

Next, a carbon coating layer was formed on the surface of the second Al-Si composite while flowing acetylene gas at 700 캜 for 10 minutes into the second Al-Si composite. Thereafter, this was used as an anode active material for a lithium secondary battery.

Examples 2 to 4

Oxidized M-Si composite used as a negative electrode active material for a lithium secondary battery was obtained in the same manner as in Example 1, except that the oxidation time was 20 minutes, 30 minutes, and 60 minutes.

Examples 5 to 8

An oxidized M-Si composite used as a negative electrode active material for a lithium secondary battery was obtained in the same manner as in Example 1 except that the oxidation temperature was 700, 740, 760, 790 캜.

Comparative Example 1

3 g of phosphoric acid, 3 wt% of nitric acid, 3 wt% of acetic acid and 21 wt% of distilled water were added to 3 g of an Al-Si crystal composite (Al _y Si _z , 80? _Y? 90, 10? _Z? Was added to the mixed etching solution and stirred at room temperature for 90 minutes to prepare a porous first Al-Si composite in which a predetermined amount of aluminum (Al) was removed. Thereafter, the aluminum-silicon powder was washed three times using an excessive amount of water, and then dried in an oven at 80 캜.

Comparative Example 2

The second M-Si composite used as a negative electrode active material for a lithium secondary battery was obtained in the same manner as in Comparative Example 1, except that the negative electrode active material was etched for 30 minutes.

Etching time
(min) Oxidation Temperature() Time (min) Example 1 30 750 10 Example 2 30 750 20 Example 3 30 750 30 Example 4 30 750 60 Example 5 30 700 60 Example 6 30 740 60 Example 7 30 760 60 Example 8 30 790 60 Comparative Example 1 90 - - Comparative Example 2 30 - -

Experimental Example

(1) Analysis of components by XRD and EDS

XRD data obtained by analyzing the components in the M-Si composite by recording the intensity of the diffracted X-ray while varying the angle (?) Of the incident X-ray continuously according to the embodiment of the present invention is shown in FIGS. 2 and 3 . Table 2 shows the EDS data.

O Al Si Example 3 Wt% 48.49 14.48 37.03 At% 62.03 10.98 26.99 Comparative Example 1 Wt% 17.71 4.37 77.92 At% 27.38 4.00 68.61 Comparative Example 2 Wt% 6.50 22.98 70.52 At% 70.78 22.60 66.62

As shown in Table 2, the content of Al was about 4 wt% in the case of Comparative Example 1 which was etched for 90 minutes, the content of Al was about 20% in the case of Comparative Example 2 which was etched for 30 minutes, It can be seen that aluminum oxide (Al ₂ O ₃ ) was formed in Example 3 in which wet oxidation was performed, considering that the content of Al was decreased and the content of O was increased.

(2) Charge-discharge characteristics and cycle characteristics

20 wt% of a binder (PAA / CMC, wt / wt = 1/1) was dispersed in water in an amount of 60 wt% of an anode active material according to Examples and Comparative Examples, a conductive material (Super P carbon black) The negative electrode slurry was coated on a 20 탆 copper foil, followed by drying and rolling to prepare a negative electrode.

A mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (having a volume ratio of 3: 7) dissolved in 1.3M of LiPF ₆ was used as the counter electrode, and lithium metal was used as a counter electrode and a polyethylene separator was interposed between the negative electrode and the counter electrode. ) Was injected to prepare a coin half-cell (CR2016 coin half-cell).

The prepared half cells were charged and discharged once at a rate of 0.05 C at a rate of 0.01 V to 3.0 V to measure an initial charge capacity, an initial discharge capacity and a coulombic efficiency. The results are shown in Table 3 and FIG. The discharge capacity was measured while performing 100 times and 300 times of charging / discharging, and the results are shown in FIGS. 5 and 6. FIG.

Charge
(mAh / g) Discharge
(mAh / g) ICE
(%) Example 1 1426 1212 85 Example 2 1320 1099 83.2 Example 3 752 605 80.5 Comparative Example 1 2730 2399 87.9 Comparative Example 2 2306 1953 84.7

As shown in Table 3 and FIG. 3 to FIG. 6, the capacities of Examples 1, 2 and 3 are smaller than those of Comparative Examples 1 and 2, but the capacity is hardly decreased even when 100 cycles and 300 cycles of charge / . It can be deduced that the lithium secondary battery using the M-Si composite as a negative electrode active material exhibits a stable cycle characteristic by forming a metal oxide core through the oxidation step to provide a stable M-Si composite.

The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

Claims (15)

A first Al-Si composite preparation step comprising silicon (Si) and aluminum (Al) in a weight ratio of 1:14 to 1: 4;
Wherein the aluminum (Al) in the first Al-Si composite is etched from the surface so that a porosity (P1) by the aluminum etching on the surface of the first Al- An etching step of obtaining a second Al-Si composite higher than the porosity (P2) by etching;
A part or the whole of aluminum (Al) in the second Al-Si composite is oxidized at a temperature of 740 to 760 캜 for 10 to 30 minutes to form a third Al-Si composite having an aluminum oxide (Al _x O _y ) An oxidation step to be obtained; And
And a second coating step of coating SiO _x (0 <x? 2) on the third Al-Si composite powder. The method according to claim 1,
The first Al-Si composite preparation step is a step of mixing a silicon (Si) powder and an aluminum (Al) powder to melt and then slowly cooling to form a first Al-Si composite, which is an Al-Si composite for a lithium secondary battery anode active material &Lt; / RTI &gt; delete The method according to claim 1,
Wherein the etching step comprises etching the aluminum (Al) of the first Al-Si composite at a temperature of 5 캜 to 25 캜 for 10 minutes to 60 minutes using an etchant, wherein the Al-Si composite for a lithium secondary battery anode active material Gt; 5. The method of claim 4,
The etching solution is phosphoric acid (H ₃ PO _4), nitric acid (HNO _3), acetic acid (CH ₃ COOH), hydrochloric acid (HCl), sulfuric acid (H ₂ SO _4), J. ferric chloride (Fe ₂ Cl), aqueous ammonia (NH ₄ OH ), Hydrogen peroxide (H ₂ O ₂ ) and hydrogen fluoride (HF). The method for producing an Al-Si composite for a lithium secondary battery anode active material according to claim 1, The method according to claim 1,
Wherein the oxidizing is a step of oxidizing the second Al-Si composite under oxygen (O ₂ ) and water vapor (H ₂ O). delete delete The method according to claim 6,
Further comprising a first coating step of coating carbon on the surface of the third Al-Si composite after the oxidation step. delete An Al-Si composite including silicon (Si) and aluminum (Al) and having an aluminum oxide (Al _x O _y ) core,
The porosity (P1) at the surface of the Al-Si composite is higher than the porosity (P2) at the center of the Al-Si composite,
Part or all of the aluminum (Al) is aluminum oxide (Al _x O _y )
The aluminum oxide (Al _x O _y ) is included in the core at 20% to 60% of the weight of the Al-Si composite,
Wherein the Al-Si composite includes an SiO _x (0 < x? 2) coating layer on at least a part of an outer surface thereof. delete 12. The method of claim 11,
Wherein the Al-Si composite has an average particle diameter of 10 to 12 占 퐉. 14. The method according to claim 11 or 13,
Wherein the Al-Si composite further comprises a carbon coating layer on at least a part of an outer surface of the Al-Si composite. delete

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