KR20140083629A - Negative electrode active material and lithium secondary battery using the same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery and the lithium secondary battery using the same. The negative electrode active material for the lithium secondary battery according to the present invention includes silicon mono-oxide with a metal catalyst deposited on a surface thereof and a silicon nanowire which is formed on the metal catalyst.

Description

[0001] The present invention relates to a negative electrode active material for a lithium secondary battery, and a lithium secondary battery using the same. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

The present invention relates to a silicon-based anode active material for a lithium secondary battery and a lithium secondary battery using the same.

The lithium secondary battery, which is one of the secondary batteries, includes a lithium secondary battery as well as a lithium ion secondary battery and has high voltage and energy density and is attracting attention as a power source for driving electronic devices. The lithium secondary battery is composed of an anode, a cathode, an electrolyte, and a separator. The lithium ions in the electrolyte move toward the cathode when charged and toward the anode when discharged, thereby discharging or absorbing surplus electrons from each electrode Causing a chemical reaction, thereby generating electrical energy. Generally, a carbon-based material such as graphite is mainly used as a negative electrode active material of a lithium secondary battery. The theoretical capacity density of graphite is 372 mAh / g. Considering the capacity loss, the actual discharge capacity density falls to about 310 to 330 mAh / g, and a carbon material capable of absorbing, storing and discharging lithium ions with a capacity density higher than that And a demand for a battery having a higher energy density is increasing. For example, U.S. Published Patent Application No. 2011-0281156 discloses that silicon having a capacity density of at least 10 times that of graphite is combined with graphite or carbon to be used as an anode active material However, the cycle characteristics are not good, the volume change due to charge reversal is very large, and the active material is undifferentiated and peeling may occur from the current collector, resulting in increased battery resistance, resulting in a problem of capacity and life span degradation.

U.S. Published Patent Application No. 2011-0281156 (Nov. 17, 2011)

Disclosure of Invention Technical Problem [8] The present invention provides a negative electrode active material for a lithium secondary battery, which can exhibit a high capacity and a high stability as well as a cycle property and can remarkably reduce a production cost by a simple process. Lithium provides a secondary battery.

The negative electrode active material for a lithium secondary battery according to the present invention includes a silicon monoxide deposited on a surface of a metal catalyst and a carbon / silicon nanowire composite formed on the metal catalyst.

The anode active material for a lithium secondary battery according to an embodiment of the present invention may have a diameter of 5 nm to 500 nm.

The aspect ratio of the silicon nanowire may be 5 to 1000 in the anode active material for a lithium secondary battery according to an embodiment of the present invention.

The negative electrode active material for a lithium secondary battery according to an embodiment of the present invention may include one or more metals selected from silver, nickel, gold, platinum, copper, cobalt, molybdenum, ruthenium, iridium, iron and manganese .

The negative electrode active material for a lithium secondary battery according to an embodiment of the present invention may have a metal catalyst in an amount of 0.01 to 1.0 wt% based on the amount of silicon monoxide.

The present invention includes a negative electrode for a lithium secondary battery containing the above-mentioned negative electrode active material.

The present invention includes a lithium secondary battery having the negative electrode described above.

A method for manufacturing a negative electrode active material for a lithium secondary battery according to the present invention includes:

Depositing metal catalyst particles on the silicon monoxide surface, and

And growing the silicon nanowires on the surface of the silicon monoxide.

In the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment of the present invention, the silicon nanowire may be a carbon / silicon nanowire composite.

In the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment of the present invention, the step of depositing the metal catalyst particles may include coating a mixture of a water-soluble polymer or a gelled polymer with a metal precursor compound on the surface of the silicon monoxide have.

In the method for manufacturing the negative electrode active material for a lithium secondary battery according to an embodiment of the present invention, the step of depositing the metal catalyst particles may be performed by any one of sputtering, physical vapor deposition, plasma enhanced chemical vapor deposition, thermochemical vapor deposition, ion beam evaporation, Laser ablation, thermal evaporation, and electron beam evaporation may be used.

In the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment of the present invention, the step of growing the silicon nanowire may include heat treatment at 1000 to 1200 ° C for 0.1 to 6 hours.

In the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment of the present invention, the metal catalyst may be at least one selected from the group consisting of silver, nickel, gold, platinum, copper, cobalt, molybdenum, ruthenium, iridium, .

In the method for manufacturing a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention, at least one of the above steps may be performed in an inert gas atmosphere.

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

The negative electrode active material for a lithium secondary battery according to the present invention can drastically improve the stability from volume expansion, undifferentiation and peeling that may occur when a negative electrode active material is reacted with an alkali ion, and can greatly improve the capacity and cycle characteristics. In addition, since the base material of silicon monoxide can be used as a source of silicon, the method of manufacturing an anode active material for a lithium secondary battery according to the present invention does not require additional supply of a silicon raw material, and thus it is not necessary to secure facilities therefor. In addition, since the carbon / silicon nanowire composite is formed on the silicon monoxide, a separate carbon coating step is not required, and the production cost can be reduced and the mass production can be achieved.

1 schematically shows a method of growing a silicon nanowire on a powder surface using a bulk SiO 2 powder coated with a metal catalyst.
2 is a SEM photograph of a negative electrode active material according to Example 1 of the present invention.
3 is a TEM photograph of a negative electrode active material according to Example 1 of the present invention.
4 shows XRD data of the negative electrode active material according to Example 1 of the present invention.
5 is a SEM photograph of a negative electrode active material according to Example 2 of the present invention.
6 is a TEM photograph of a negative electrode active material according to Example 2 of the present invention.
7 shows XRD data of the negative electrode active material according to Example 2 of the present invention.
8 shows electrochemical characteristics of the negative electrode active material according to Production Example 1 of the present invention.
9 shows the results of electrochemical characteristics of the negative electrode active material according to Production Example 2 of the present invention.
10 is a SEM photograph of the negative electrode active material according to Comparative Example 1. FIG.
11 shows the XRD data of the negative electrode active material according to Comparative Example 1
12 shows the electrochemical characteristics of the negative electrode active material according to Comparative Production Example 1. FIG.

The negative active material for a lithium secondary battery according to the present invention includes a silicon monoxide deposited on a surface of a metal catalyst and a silicon nanowire formed on the metal catalyst. That is, the anode active material for a lithium secondary battery according to the present invention has a structure of a sea urchin shape, in which a metal catalyst is deposited on the surface of a base material of silicon monoxide, and a silicon nanowire is grown on the metal catalyst.

As a result, silicon as a negative electrode active material for a lithium secondary battery realizes a high capacity, but its cycle characteristics are degraded, and the silicon monoxide has a relatively small capacity as compared with silicon. At the same time, a battery negative electrode Based anode active material having a core shell structure of silicon monoxide and silicon nanowire having a high capacity and high stability and excellent cycle characteristics since deterioration in mechanical properties due to deterioration due to volume expansion that may occur upon reaction can be improved Can be provided.

The anode active material for a lithium secondary battery according to an embodiment of the present invention may have a diameter of 5 nm to 500 nm. When the diameter of the nanowire is less than 5 nm, the nanowire is broken and short-circuiting may occur, which may cause short-circuit. If the diameter is 500 nm or more, the nanowire can not sufficiently exhibit its function, resulting in a volume expansion problem.

In the present invention, the size of the metal catalyst particles determines the size of the silicon nanowires. The metal catalyst particles preferably have an average particle diameter of 5 nm to 500 nm. If the diameter of the metal catalyst particles is less than 5 nm, the growth of the nanowires may be difficult or unexpected, and the surface area of the nanowires may be increased to cause unexpected side reactions. If the diameter of the nanowires exceeds 500 nm, And it is difficult to realize the characteristics of the nanowire.

The aspect ratio of the silicon nanowire may be 5 to 1000 in the anode active material for a lithium secondary battery according to an embodiment of the present invention. If the aspect ratio is less than 5, the amount of silicon nanowires is insufficient and it is difficult to expect a desired level of electrochemical characteristics. If the aspect ratio is more than 1000, the silicon surface area becomes too high, which may result in undesired side reactions, .

The negative electrode active material for a lithium secondary battery according to an embodiment of the present invention may include one or more metals selected from silver, nickel, gold, platinum, copper, cobalt, molybdenum, ruthenium, iridium, , But is not necessarily limited thereto.

In the anode active material for a lithium secondary battery according to an embodiment of the present invention, the metal catalyst is preferably 0.01 to 1.0 wt% of the silicon monoxide content, and when the content of the metal catalyst is more than 1 wt%, the amount of the residual metal catalyst increases, And if it is less than 0.01 wt%, the density of the silicon nanowire may be lowered.

The amount of growth of the silicon nanowire on the anode active material according to an embodiment of the present invention is preferably 5 to 80% by weight based on the weight of the silicon monoxide.

In order to stabilize the metal catalyst in the present invention, it is preferable to use poly (vinyl pyrrolidone), poly (ethylene oxide), poly (acrylic acid), poly (vinyl alcohol) vinyl alcohol, poly (methacrylic acid), and poly (lactic acid)), at the same time as the growth of the water-soluble polymer or silicon nanowire is possible (Alginate, poly (vinyl alcohol), poly (acrylic acid) / poly (vinyl alcohol)) such as agarose can be used. This is because the metal catalyst is coated and stabilized on the silicon monoxide during the manufacturing process of the anode active material, and remains as a carbon source when the heat treatment is performed at a high temperature to grow the silicon nanowire, thereby forming the silicon nanowire and the carbon silicon nanowire composite . In addition, carbon remaining in the carbon source when reacted with the metal catalyst forms a carbon nanotube and is entangled with the silicon nanowire in a three-dimensional manner, thereby remarkably increasing the electrical conductivity.

The present invention includes a negative electrode for a lithium secondary battery containing the above-mentioned negative electrode active material.

The lithium secondary battery having the negative electrode active material according to the present invention includes a negative electrode including a negative electrode active material, a positive electrode including a positive electrode active material, and an ion conductor, and the negative electrode may further include a binder or a current collector. It is possible to further include a known negative active material in addition to the negative active material according to the embodiment.

The present invention includes a lithium secondary battery having the negative electrode described above.

The lithium secondary battery according to one embodiment of the present invention includes a cathode, an anode, a separator between the cathode and the anode, an ion conductor impregnated in the cathode, the anode and the separator, and a sealing material sealing the battery container and the electric container Lt; / RTI >

In this case, the anode may contain a cathode active material conventionally used in a secondary battery. Examples of the cathode active material include a Li-MP system (M is at least one selected from the group consisting of Fe, Mn, Co and Ni), Li -Mn-Ni system, and a Li-Ni-Mn-Co system lithium composite oxide.

In this case, the electrolyte may include a non-aqueous electrolyte commonly used in a secondary battery. Examples of the electrolyte include a liquid electrolyte in which a lithium salt including lithium perchlorate and lithium borofluoride is dissolved in a solvent. Examples thereof include ester solvents including propylene carbonate, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

In this case, the separation membrane may include a separation membrane that is conventionally used in a secondary battery to prevent a short circuit between the cathode and the anode in the secondary battery, and may also support the electrolyte. Examples of the separator include microporous membranes including polyethylene, polypropylene, and polyolefin, and organic membranes such as a plurality of polyethylene membranes, polypropylene membranes, and nonwoven fabrics may be stacked to prevent overcurrent, And may have a laminated structure.

A method for manufacturing a negative electrode active material for a lithium secondary battery according to the present invention includes:

Depositing metal catalyst particles on the silicon monoxide surface, and

And growing the silicon nanowires on the surface of the silicon monoxide.

At this time, the step of depositing the metal catalyst particles may include coating metal particles from a mixture of a water-soluble polymer such as a surfactant and a metal precursor, or coating a metal particle from a mixture of a gelling polymer such as agarose and a metal precursor The metal catalyst may be coated on the silicon monoxide to stabilize the silicon nanowire and remain as a carbon source during the heat treatment at a high temperature to grow the silicon nanowire to form a carbon nanowire and carbon nanowire composite.

 In the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment of the present invention, the step of growing the silicon nanowire is preferably performed at a temperature at which the silicon monoxide is decomposed into silicon and silica. At this time, the disassembled silicon is provided as a growth source of the silicon nanowire, so that there is an advantage that the yield can be increased by a simple process without requiring additional supply of the silicon raw material.

In the present invention, if the metal catalyst particles are coated with a water-soluble polymer or a gelated polymer, a carbon / silicon nanowire composite may be formed on the surface of the silicon monoxide by further performing a heat treatment process for growing the silicon nanowire. At this time, the heat treatment is preferably performed at a temperature of 50 to 100 ° C or higher, preferably 1000 to 1200 ° C, for 0.1 to 6 hours, which is higher than the eutectic temperature of the metal silicide formed by the reaction between the metal catalyst and silicon.

In the method of manufacturing an anode active material according to an embodiment of the present invention, the diameter, the length, and the aspect ratio of the silicon nanowire may be varied depending on the specification of the silicon monoxide or the particle diameter of the metal catalyst particles and the heat treatment temperature and / It is possible to improve the physical properties.

In the method of manufacturing an anode active material for a lithium secondary battery according to an embodiment of the present invention, the metal catalyst may be at least one selected from the group consisting of silver, nickel, gold, platinum, copper, cobalt, molybdenum, ruthenium, iridium, .

In the method for manufacturing a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention, at least one of the above steps may be performed in an inert gas atmosphere.

Hereinafter, the present invention will be better understood by reference to the following examples, and the following examples are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[Example 1]

2 g of silicon monoxide powder (Sigma Aldrich, Silicon mono oxide), 0.2 g of polyvinylpyrrolidone (Sigma Aldrich, polyvinylpyrrolidone) and 7 g of water were placed in a glass vial and stirred at 100 ° C for 1 hour. Thereafter, 20 mg of NiCl 2 was added as a nickel source, and the mixture was stirred at 100 ° C for 1 hour. After the stirring, the unreacted polyvinylpyrrolidone was removed by washing with ethanol, and a polyvinylpyrrolidone-coated silicon monoxide powder containing a metal precursor was obtained through a filter. The sample was dried in an oven at 80 DEG C for 12 hours and at 70 DEG C in a vacuum oven for 24 hours to completely remove the water of the obtained sample. Next, in order to grow silicon nanowires, heat treatment was performed in an alumina oven at 500 ° C. for 30 minutes and at 1050 ° C. for 2 hours in an argon atmosphere to form a silicon nano wire grown on the silicon monoxide, .

 [Example 2]

A gel-like sample was prepared in the same manner as in Example 1, except that 0.2 g of agarose (Agarose, Sigma Aldrich, Type IB) was added in place of polyvinylpyrrolidone and 7.3 g of water was added. , Which was dried for 12 hours in an 80 ° C oven and for 24 hours in a 70 ° C vacuum oven. Next, in order to grow silicon nanowires, heat treatment was performed in an alumina oven at 500 ° C. for 30 minutes and at 1050 ° C. for 2 hours in an argon atmosphere to form a silicon nano wire grown on the silicon monoxide, .

[Production Example 1]

(PAA / CMC, wt / wt = 1/1) (20) weight% of the negative electrode active material (60) for a lithium secondary battery prepared in Example 1, the weight of the conductive material (Super P carbon black) Was dispersed in water to prepare an anode slurry. The negative electrode slurry was coated on a copper foil, followed by drying and rolling to prepare a negative electrode. (3: 7 volume ratio) of ethylene carbonate (EC) and dimethyl carbonate (DMC) dissolved in 1.3 M of LiPF6 was used as the anode, and a polyethylene separator was interposed between the anode and the cathode. Was injected to prepare a coin cell (half-cell).

[Production Example 2]

A coin cell was prepared in the same manner as in Production Example 1, except that the negative electrode active material of Example 2 was used.

[Comparative Example 1]

In Comparative Example 1, 2 g of silicon monoxide powder (Sigma Aldrich) was subjected to a heat treatment in an alumina oven at 1050 ° C for 2 hours under an argon atmosphere to cause the silicon monoxide to decompose into silicon and silica. By this method, the silicon monoxide produced a material composed of silicon particles and a silica matrix inside.

[Comparative Production Example 1]

A coin cell was produced in the same manner as in Production Example 1, except that the negative electrode active material of Comparative Example 1 was used.

Since the negative electrode active material according to the present invention is excellent in high capacity, high stability, and cycle characteristics, and is not particularly required to be supplied externally with a silicon source, it is not subjected to a number of steps, There is an advantage that a negative electrode active material for a lithium secondary battery in which silicon nanowires are grown on a silicon monoxide can be mass produced by a simple process.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (15)

1. A negative active material for a lithium secondary battery, comprising: a silicon monoxide deposited on a surface of a metal catalyst; and a silicon nanowire formed on the metal catalyst. The method according to claim 1,
Wherein the silicon nanowire is a silicon / carbon nanowire composite. The method according to claim 1,
The silicon nanowire is a negative electrode active material for a lithium secondary battery having a diameter of 5 to 500 nm. The method according to claim 1,
The silicon nanowire is an anode active material for a lithium secondary battery having an aspect ratio of 5 to 1000. The method according to claim 1,
Wherein the metal catalyst comprises one or more selected from the group consisting of silver, nickel, gold, platinum, copper, cobalt, molybdenum, ruthenium, iridium, iron and manganese. The method according to claim 1,
Wherein the metal catalyst is 0.01 to 1.0 wt% based on the weight of the silicon monoxide.
Wherein the growth amount of the silicon nanowires on the anode active material is 5 to 80% by weight based on the weight of the silicon monoxide, and the aspect ratio of the silicon nanowires on the anode active material is 5 to 1000 or less. Depositing metal catalyst particles on the silicon monoxide surface, and
And growing a silicon nanowire on the surface of the silicon monoxide. 8. The method of claim 7,
Wherein the silicon nanowire is a carbon / silicon nanowire composite. 8. The method of claim 7,
The step of depositing the metal catalyst particles may include depositing a metal oxide on the surface of the silicon monoxide layer using polyvinyl pyrrolidone, poly (ethylene oxide), poly (acrylic acid), polyvinyl alcohol soluble polymer or an agarose selected from the group consisting of poly (vinyl alcohol), poly (methacrylic acid) and poly (lactic acid), and alginic acid and a mixture of a polymer capable of gelation and a metal precursor compound selected from the group consisting of alginate and alginate is coated on the surface of the negative electrode active material for lithium secondary battery. 8. The method of claim 7,
The step of depositing the metal catalyst particles may be performed by a vapor deposition method selected from the group consisting of sputtering, physical vapor deposition, plasma enhanced chemical vapor deposition, thermochemical vapor deposition, ion beam evaporation, vacuum thermal evaporation, laser ablation, thermal evaporation and electron beam evaporation Wherein the negative electrode active material is deposited by a sputtering method. 8. The method of claim 7,
Wherein the step of growing the silicon nanowires is performed at 1000 to 1200 占 폚. 8. The method of claim 7,
Wherein the step of growing the silicon nanowire further comprises a heat treatment at 1000 to 1100 ° C for 0.1 to 6 hours. 8. The method of claim 7,
Wherein the metal catalyst comprises one or more selected from the group consisting of silver, nickel, gold, platinum, copper, cobalt, molybdenum, ruthenium, iridium, iron and manganese. 8. The method of claim 7,
Wherein at least one of the steps is performed in an inert gas atmosphere. A lithium secondary battery comprising a negative active material according to any one of claims 1 to 6 or a negative active material according to any one of claims 7 to 14.

Images