KR20140018569A - Preparation of bimetallic alloys loaded activated carbon nanotubes as anode materials for secondary batteries - Google Patents

Abstract

The present invention relates to a method for producing activated carbon nanotubes carrying a bimetalic alloy for secondary battery anode materials. More particularly, the present invention relates to a carbon material and a high capacity alternative material which can be easily used as a cathode material of a lithium secondary battery. High capacity and excellent cycles through the compounding of high capacity metal materials that can form alloys with lithium ions such as aluminum (Al), silicon (Si), tin (Sn), bismuth (Bi) and antimony (Sb) The present invention relates to an activated carbon nanotube composite having a heterogeneous alloy for a lithium secondary battery negative electrode material having a new concept and a method of manufacturing the same.
The hetero carbon-supported activated carbon nanotube composite according to the present invention exhibits a high metal dispersion ratio and a supported amount, and a significantly improved energy capacity than conventional carbon nanotubes, and has a new concept of superior cycle and mechanical properties than conventional alloy materials. It can be usefully used for the lithium secondary battery negative electrode material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an active carbon nanotube,

The present invention relates to a method for producing activated carbon nanotubes on which a bimetalic alloy for a secondary battery anode material is carried, and more particularly, to a carbon material and a high-capacity alternative material which can be easily used as an anode material of a lithium secondary battery The combination of high-capacity metal materials that can be alloyed with lithium ions such as aluminum (Al), silicon (Si), tin (Sn), bismuth (Bi), and antimony (Sb) The present invention relates to a novel concept of an activated carbon nanotube composite on which a heterogeneous alloy for a lithium secondary battery anode material is supported, and a manufacturing method thereof.

The graphite material widely used as an anode material of a lithium secondary battery has a small volume change during charging and discharging, but the theoretical value of the electric capacity is very low as 372 mAh / g. Therefore, the high efficiency, And it is a limitation in developing a battery having high performance.

As an alternative to this, a silicon material having a theoretical capacity of 4,200 mAh / g is being developed as a next generation anode material, but a pure silicon anode material has a volume change of 300% during charging and discharging, It is difficult to use it as an anode material.

2. Description of the Related Art Recently, metal particles such as tin (Sn), antimony (Sb), bismuth (Bi), and silicon (Si) have been combined with carbon materials such as carbon nanotubes to form composites. Mater. Lett. 62 (2008) 2092-2095; Carbon 45 (2007) 1396-1409). It is expected that the life of the anode material will be greatly improved by the stability of the structure formed when these materials are nano-structured.

Among them, the anode material based on silicon has the high efficiency of 4,200 mAh / g when Li _4,4 Si is theoretically theoretically attracted to the next generation anode material. However, due to the volume change during charging and discharging There is a great deal of difficulty in using the anode material directly because of the reduced efficiency (after 10 repetitions, the rapid decrease of the capacitance) and the low electrical conductivity of the pure silicon material.

As a result of intensive efforts to develop an innovative lithium secondary battery anode material based on a carbon material, the present inventors have found that by combining a bimetallic alloy of activated carbon or nattove and Sn and Sb produced by a high temperature vapor activation method, And an excellent cycle characteristic, and completed the present invention.

It is a main object of the present invention to provide an activated carbon nanotube composite having a new concept of a bimetallic alloy for a lithium secondary battery anode material and a method of manufacturing the same.

In order to accomplish the above object, the present invention provides a method for producing a lithium secondary battery anode material, which is obtained by combining a carbon nanotube and a bimetallic alloy of Sn and Sb prepared by a high temperature vapor phase activation method, Lt; / RTI >

In addition, the present invention provides a nanoscale fine metal particle support by easily opening the end of a carbon nanotube by a high temperature vapor phase activation method, introducing a large amount of active sites on the surface thereof, introducing fine metal particles whose size and amount are controlled, And immobilizing the fine particles into the tube of the activated carbon or the nitrogen and the inside of the inter-tube web.

In accordance with the present invention, the present invention provides a method for activating carbon nanotubes having a high specific surface area by opening a large amount of the ends of carbon nanotubes by a high temperature vapor activation method using carbon dioxide gas, and a nanoscale fine metal particle support, It is possible to precisely control the content and dispersion ratio of the metal microparticles of the metal / activated carbon / nitrogen composite.

In addition, in the process of introducing fine metal particles through a chemical reduction method of a suspension of Sn / Sb and activated carbon nanotubes, the dissimilar metal particles are immobilized in the tube-inserted web of the activated carbon nanotube or the nanotube.

As a result, the activated carbon nanotube composite supporting the different alloy of the present invention exhibits a high metal dispersion ratio, a supported amount, and a significantly improved energy capacity compared to the conventional carbon nanotubes, and is a new concept having cycle characteristics and mechanical characteristics Of lithium secondary battery negative electrode material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a TEM photograph of an activated carbon or a nitrogen-containing activated carbon prepared according to an embodiment of the present invention.
2 is a TEM photograph of an activated carbon nanotube composite on which a heterogeneous alloy is supported according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention provides an activated carbon nanotube composite on which a bimetallic alloy is supported.

In the present invention, the activated carbon nanotube composite may be prepared by mixing activated carbon nanotubes prepared by a high temperature vapor phase activation method and a metal such as silicon (Si), indium (In), lead (Pb), gallium (Ga), germanium (Ge) ), Aluminum (Al), bismuth (Bi), antimony (Sb), and the like.

Preferably, the activated carbon nanotube composite is an alloy of Sn and Sb with activated carbon nanotubes prepared by a high temperature vapor activation method.

At this time, the alloy ratio of Sn / Sb is preferably 0.01 to 99.99, more preferably 0.1 to 10.

The present invention also provides a method for producing an activated carbon nanotube composite on which a heterogeneous alloy is supported.

Specifically, the method comprises the steps of: 1) preparing an activated carbon or a nitrogen-containing activated carbon nanotube having a large number of active sites on the surface of the outer wall of the carbon nanotube, the nanotube being exposed on the surface of the carbon nanotube by a high temperature vapor activation method using carbon dioxide gas; 2) introducing fine metal particles having controlled size and amount of metal fine particles into the activated carbon or the nitrogen through the chemical reduction method; And 3) fixing the fine metal particles introduced into the activated carbon nanotube into the tube and the inter-tube web.

In the present invention, in the step 1), the ends of the carbon nanotubes formed in the form of a ring-like one-to-ten-folded graphite surface are opened to form nano pores on the surface of the outer wall of the carbon nanotube, Thereby increasing the surface area, and at the same time, giving active points for introduction of the metal fine particles.

The carbon nanotubes may be selected from activated carbon, activated carbon fibers, pitch nanofibers, graphite oxides, graphene oxides, single wall carbon nanotubes, double wall carbon nanotubes, and multiwall carbon nanotubes Is preferably used.

It is preferable that at least one of inert gases such as nitrogen, helium, and argon is used as the atmosphere in the reactor during the temperature raising process at a high temperature, and the rate of temperature increase is 1 to 5 ° C / min. The temperature is preferably 400 to 1,500 占 폚.

When the gas phase activation temperature is lower than 400 ° C., when the ends of the carbon nanotubes are not opened or nano pores are not formed on the outer wall surface of the carbon nanotubes, and when the temperature is higher than 1,500 ° C., the collapse of the formed nanopores, The yield of the nitrogen can be lowered.

The gas phase activation time is preferably 5 minutes to 2 hours, more preferably 10 minutes to 60 minutes, and the flow rate of the active gas is preferably 10 to 500 cc / min.

Excessive treatment time and gas inflow amount are undesirable because they reduce the yield of produced activated carbon or nitrogen. In addition, the active gas used for the gas phase activation can be any of commonly used active gases such as carbon dioxide, oxygen, air, hydrogen sulfide, sulfurized oxidizing gas, nitrided oxidizing gas and ammonia.

In the step 2), the metal fine particles are introduced into the activated carbon or the nitrogen-containing activated carbon, to which the active end point of the step 1) is opened and the surface of the outer wall is exposed with nanopores. In this case, It is preferable to use two kinds of alloy metals selected from Si, In, Pb, Ga, Ge, Sn, Al, Bi, Although the metal is not limited in any way, an alloy of Sn and Sb is mainly used in view of the high capacity and economical efficiency of the anode material of the lithium secondary battery. At this time, the alloy ratio of Sn / Sb introduced is preferably 0.01 to 99.99, more preferably 0.1 to 10.

Furthermore, the active sites expressed in the tube and on the outer wall of the tube of the activated carbon nanotube act as a nucleation site of the metal microparticles and induce precipitation of the metal microparticles.

In the step of introducing the metal, the introduction amount of the metal is preferably 0.01 to 70 wt.%, More preferably 0.05 to 50 wt.%, Based on the weight of the activated carbon or the nitrogen.

Further, the metal precursor used for introducing the metal fine particles is preferably a composite of at least one element selected from chloride, nitrate, hydrazine, sulfate, phosphate, citrate, and the like.

In addition, in the step 2), in order to reduce the metal ion from the bimetallic metal ion compound, a reducing agent such as sodium hydroxide (NaOH), sodium borohydride (NaBH ₄ ), lithium aluminum hydride (LiAlH ₄ ) It is preferred to add a paraffin or a mixture thereof.

The pH atmosphere is preferably in the range of 7.0 to 13.0.

In the step 3), in order to control the size of the fine metal particles and to fix the activated carbon or the nanotube into the tube and fix the nanotube in a highly dispersed state in the inter-tube web, an activated carbon or a nitrogen-containing mixture of a metal ion compound and a reducing solvent is ultrasonically And then treated for 1 minute to 24 hours. After the ultrasonic treatment, the activated carbon or the nitrogen containing the heterogeneous alloy is filtered using a membrane filter, and then washed with a volatile solvent such as distilled water or anhydrous chloroform, ethanol or acetone to remove residual impurities or undissolved organic substances , And dried in a vacuum oven at 100 to 150 ° C for 24 to 72 hours to prepare an activated carbon nanotube composite bearing a heterogeneous alloy.

The activated carbon nanotube composite having the above-prepared heterogeneous alloy has an initial energy storage capacity of 450 to 2,000 mAh / g and an energy storage capacity of 55 to 95% after 500 charge / discharge cycles.

Therefore, the activated carbon nanotube composite supporting the hetero alloy of the present invention can be usefully used as a new concept lithium secondary battery anode material having a high capacity and excellent cycle characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these examples are for illustrative purposes only and that the scope of the present invention is not construed as being limited by these examples.

Measurement example 1. Observation of surface of activated carbon nanotube complex bearing heterogeneous alloy

The surface of the activated carbon nanotube composite on which the heterogeneous alloy for lithium secondary battery negative electrode material was prepared according to the present invention was observed with a transmission electron microscope (TEM; JEM2100F, JEOL, Japan).

Measurement example 2. Observation of the capacity and cycle characteristics of the activated carbon nanotube complex carrying the different alloy

The cyclic voltammetry (CV) method was used to measure the change of the energy storage capacity according to the charge-discharge characteristics and the number of times of charging and discharging of the activated carbon nanotube composite electrode supported on the heterogeneous alloy for a lithium secondary battery anode material manufactured according to the present invention. .

Example 1.

After the distilled water and ethanol 1 g of carbon nanotubes at room temperature stirred for 12 hours in a solution mixture of the same volume ratio of the completely washed and dried, placed in a tubular furnace in a nitrogen (N ₂₎ atmosphere at a heating rate of 2 ℃ / min. And the temperature was raised to 1,000 ° C. Subsequently, carbon dioxide (CO ₂ ) gas was introduced at a flow rate of 250 cc / min at 1000 ° C, vapor-phase activated for 30 minutes, and cooled to room temperature.

The prepared activated carbon nanotubes were washed once or twice in distilled water, vacuum-dried at 120 ° C. for 12 hours or more, mixed with carbon black and poly (vinylidene fluoride) at a weight ratio of 70:20:10 Cast into an aluminum foil as a collector, vacuum dried at 120 DEG C for 24 hours to remove residual solvent, and used as a negative electrode.

A coin cell was fabricated using lithium metal as the anode material.

Example 2.

2 g of the carbon nanotubes were thoroughly washed by stirring at room temperature for 12 hours in a mixed solution of distilled water and ethanol at the same volume ratio, and then dried and placed in a tubular furnace and heated at a rate of 2 ° C / min in a nitrogen (N ₂ ) atmosphere And the temperature was raised to 1,000 ° C. Subsequently, carbon dioxide (CO ₂ ) gas was introduced at a flow rate of 250 cc / min at 1000 ° C, vapor-phase activated for 30 minutes, and cooled to room temperature.

The prepared activated carbon nanotubes were washed once or twice in distilled water, vacuum-dried at 120 ° C. for 12 hours or more, and 1 g of the activated carbon nanotubes was introduced into a prepared activated carbon nanotube, 3 g of SnCl ₂ .2H ₂ O, Aldrich, 98%) and 2 g of Sb chloride (SbCl ₃ , Aldrich, 98%) were dissolved in 300 ml of ethylene glycol solution and stirred vigorously for 4 hours.

Then, the mixture was poured into 50 ml of a 5 M aqueous solution of lithium aluminum hydride (LiAlH ₄ ), the pH of the mixture was adjusted to an alkaline atmosphere (pH 10-13), and the mixture was stirred for 4 hours. The mixture was transferred to an ultrasonic device for 2 hours After 3 ml of formaldehyde was added, the temperature was slowly raised, and the mixture was ultrasonicated at 120 ° C for 10 minutes and cooled to room temperature.

The heterogeneous alloy / activated carbon nanotube composite supported with the heterogeneous alloy thus prepared was thoroughly washed with distilled water and acetone, respectively, and completely dried at 120 ° C. for 12 hours or more. At this time, the chemical reduction process of introducing the heterogeneous alloy was performed in a nitrogen (N ₂ ) atmosphere.

The dried heterogeneous metal / activated carbon nanotube composite was washed 1-2 times in distilled water, vacuum-dried at 120 ° C for 12 hours, mixed with carbon black and poly (vinylidene fluoride) at a weight ratio of 70:20:10 The collector was cast in an aluminum foil, vacuum dried at 120 ° C for 24 hours to remove residual solvent, and used as a negative electrode. Lithium metal was used as a positive electrode material to prepare a coin cell.

Comparative Example 1

By distilled water and ethanol, 2 g of carbon nanotubes at room temperature, stirred for 12 hours in a solution mixture of the same volume ratio fully washed and then dried into a tubular furnace in a nitrogen (N ₂₎ atmosphere at a heating rate of 2 ℃ / min. 350 Lt; 0 > C. Subsequently, carbon dioxide (CO ₂ ) gas was introduced at a flow rate of 250 cc / min at 350 ° C, vapor-phase activated for 300 minutes, and cooled to room temperature.

The carbon nanotubes were washed once or twice in distilled water, vacuum-dried at 120 ° C. for 12 hours or more, mixed with carbon black and poly (vinylidene fluoride) at a weight ratio of 70: 20: 10, After casting in a foil, it was vacuum dried at 120 ° C for 24 hours to remove residual solvent, and used as a negative electrode, and a coin cell was produced using lithium metal as a positive electrode material.

Comparative Example 2

In order to introduce fine metal particles into the washed and dried carbon nanotubes in the same manner as in Comparative Example 1, 1 g of the carbon nanotubes was dissolved in 300 ml of 3 g of Sn chloride (SnCl ₂ .2H ₂ O, Aldrich, 98% Of ethylene glycol solution, and the mixture was stirred vigorously for 4 hours.

Then, the mixture was poured into 50 ml of a 5 M aqueous solution of lithium aluminum hydride (LiAlH ₄ ) to adjust the pH of the mixture, followed by weak stirring for 4 hours. Then, the mixed solution was transferred to an ultrasonic device for 2 hours, and 3 ml of formaldehyde After slowly warming, the mixture was ultrasonicated at 120 DEG C for 10 minutes and cooled to room temperature.

The metal / activated carbon nanotube composite supported on the metal fine particles thus prepared was thoroughly washed with distilled water and acetone, and dried at 120 ° C for more than 12 hours. At this time, the chemical reduction process of introducing the heterogeneous alloy was performed in a nitrogen (N ₂ ) atmosphere.

The dried metal / activated carbon nanotube composite was washed once or twice in distilled water, vacuum-dried at 120 ° C. for 12 hours, mixed with carbon black and poly (vinylidene fluoride) at a weight ratio of 70: 20: The whole was cast in an aluminum foil, vacuum dried at 120 DEG C for 24 hours to remove residual solvent, and used as a negative electrode. Lithium metal was used as a positive electrode material to prepare a coin cell.

Conditions for manufacturing the activated carbon nanotube complex agent containing the different alloy for the lithium secondary battery anode material according to the present invention division Activation condition
(Active gas / temperature (占 폚) / hour (minute)) Metal type Amount of metal supported (wt.%) Relative to weight of carbon support Ultrasonic processing time
(time) Example 1 CO ₂ / 1,000 / 30 - - - Example 2 CO ₂ / 1,000 / 30 Sn, Sb 2.5 2 Comparative Example 1 CO _2/350/5 - - - Comparative Example 2 - Sn 1.5 -

The initial energy storage capacity and cycle characteristics of the activated carbon nanotube complex supported on the different alloy for the lithium secondary battery anode material according to the present invention division Initial energy storage capacity
(MAh / g) Cycle characteristics
(After 500 times, energy storage capacity) Example 1 470 400 Example 2 1,800 1,550 Comparative Example 1 275 195 Comparative Example 2 435 115

Having described specific portions of the present invention in detail, those skilled in the art will appreciate that these specific descriptions are only for the preferred embodiment and that the scope of the present invention is not limited thereby. It will be obvious. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (18)

Activated carbon nanotube composite loaded with a bimetallic alloy.
The method of claim 1,
The heteroalloy is formed of silicon (Si), indium (In), lead (Pb), gallium (Ga), germanium (Ge), tin (Sn), aluminum (Al), bismuth (Bi), and antimony (Sb). Activated carbon nanotube composite loaded with a bimetallic alloy, characterized in that the selected two kinds of alloy metal.
3. The method of claim 2,
The hetero-alloy is an activated carbon nanotube composite loaded with a bimetallic alloy, characterized in that the alloy of tin (Sn) and tin (Sn).
The method of claim 3, wherein
The alloy ratio of the tin (Sn) / tin (Sn) is an activated carbon nanotube composite loaded with a bimetallic alloy, characterized in that 0.01 to 99.99.
The method of claim 1,
The initial carbon storage capacity of the activated carbon nanotube composite is 450 to 2,000 mAh / g, the activated carbon nanotube composite loaded with a bimetallic alloy (bimetallic alloy).
The method of claim 1,
The energy storage capacity after 500 times of charge and discharge of the activated carbon nanotube composite is an activated carbon nanotube composite loaded with a bimetallic alloy, characterized in that 55 to 95% of the initial energy storage capacity.
1) preparing activated carbon nanotubes having a large amount of active points in which carbon nanotubes are open at the ends of the carbon nanotubes and nanopores are expressed on the surface of the outer wall by carbon dioxide gas;
2) introducing the metal fine particles having a controlled size and loading of the metal fine particles through the chemical reduction method into the activated carbon nanotubes; And
3) inserting the metal fine particles introduced into the activated carbon nanotubes into the tube and fixing them in the inter-tube web; a method of manufacturing an activated carbon nanotube composite loaded with a bimetallic alloy comprising a.
8. The method of claim 7,
The carbon nanotubes are selected from activated carbon, activated carbon fibers, pitch-based nanofibers, graphite oxide, graphene, graphene oxide, single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes 1 The production method characterized by the above-mentioned species.
8. The method of claim 7,
The high temperature gas phase activation of step 1) is the atmosphere in the reactor during the temperature increase process using at least one inert gas selected from nitrogen, helium, and argon, the temperature increase rate is 1 to 5 ℃ / min. The manufacturing method characterized in that the 400 to 1,500 ℃.
8. The method of claim 7,
The high temperature gas phase activation time of step 1) is 5 minutes to 2 hours, and the inflow rate of the active gas selected from carbon dioxide, oxygen, air, hydrogen sulfide, sulfur sulfide gas, nitric oxide gas and ammonia is 10 to 500 mW / min. Production method characterized in that.
8. The method of claim 7,
The metal fine particles of step 2) are silicon (Si), indium (In), lead (Pb), gallium (Ga), germanium (Ge), tin (Sn), aluminum (Al), which are metals reacting with lithium ions. Bismuth (Bi) and antimony (Sb) is a manufacturing method characterized in that the two kinds of alloy metals.
12. The method of claim 11,
The metal particulate is a manufacturing method characterized in that the alloy of tin (Sn) and tin (Sn).
13. The method of claim 12,
The alloy ratio of the tin (Sn) / tin (Sn) is a manufacturing method, characterized in that 0.01 to 99.99.
8. The method of claim 7,
The amount of metal introduced in step 2) is 0.01 to 70 wt.%, Based on the weight of activated carbon nanotubes.
8. The method of claim 7,
At least one selected from sodium hydroxide (NaOH), sodium borohydride (NaBH ₄ ), and lithium aluminum hydride (LiAlH ₄ ) as a reducing solvent to reduce metal ions in the bimetallic metal ion compound in step 2). Method for producing a metal hydride.
8. The method of claim 7,
The step 3) is characterized in that the production method is made in the range of pH 7.0 to 13.0.
8. The method of claim 7,
In order to control the size of the metal fine particles and to insert the activated carbon nanotubes into the tube and to fix the highly dispersed in the web between the tubes, the activated carbon nanotubes containing the metal ion compound and the reducing solvent were mixed for 1 minute to 24 minutes using an ultrasonic apparatus. Process for producing a time characterized in that.
8. The method of claim 7,
After step 3),
Activated carbon nanotubes loaded with different alloys were filtered using a membrane filler, and then washed with a volatile solvent to remove residual impurities or unsynthetic organic substances, and dried at 100 to 150 ° C. for 24 to 72 hours using a vacuum oven. The manufacturing method characterized in that it further comprises.

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