KR101977237B1 - Method for manufacturing composite including soil having iron and iron compound and carbon, and negative electrode material for secondary battery having the composite manufactured thereby - Google Patents

Abstract

The present invention relates to a method for producing a steel sheet, comprising the steps of: (a) mixing soil and carbon (C) powder containing iron (Fe) and iron compounds as main components; And (b) mixing the soil with the carbon by applying mechanical energy to the mixed powder. According to the present invention, iron and iron compounds such as red soil are used as main components Can be economically produced by combining a soil containing carbon and carbon with a high-energy mechanical milling process to produce an anode active material having a higher capacity than a conventional graphite anode material and having an excellent cycle life as compared with a silicon anode material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite containing iron and iron compound-containing soil and carbon, and a negative electrode active material for a secondary battery, HAVING THE COMPOSITE MANUFACTURED THEREBY}

The present invention relates to a method of manufacturing a material for a secondary battery anode active material.

Lithium ion secondary batteries, which are the most widely used secondary batteries in the world, are being studied in various fields such as high capacity and high-speed charging for development of portable electronic devices and hybrid automobile applications. The anode material using lithium having the largest energy density has a theoretical capacity of 3860 mAh / g, which is higher than any other materials.

However, when lithium metal is used as a negative electrode, a large amount of dendritic lithium precipitates on the lithium surface at the time of charging, which may cause a reduction in charging / discharging efficiency, short circuit between the positive electrode and lithium, and instability of lithium itself, It is sensitive and danger of explosion, which made it difficult to commercialize.

The graphite, which is a carbonaceous anode material widely used as an anode active material to solve the problems of the conventional lithium metal, has a smaller theoretical capacity (372 mAh / g) than the lithium metal but has a small volume change, reversibility and advantages in terms of price.

However, as portable devices have become increasingly more compact, lighter, and more sophisticated, higher capacity of lithium secondary batteries has become an important issue. Therefore, despite the existing problems of metal cathodes, Studies have been actively made to improve the capacity of a battery.

As a part of this research, a lithium metal alloy metal such as silicon (Si), tin (Sn), and aluminum (Al) and a metal oxide are used as a negative electrode active material. However, materials such as silicon and metal oxides, which can be alloyed with lithium, are accompanied by volumetric expansion during the alloying reaction with lithium, generate electrically isolated active materials in the electrode, and cause electrolyte decomposition reaction And the like.

Many studies have been made to overcome the disadvantages of such lithium-alloyable metals and transition metal oxide electrodes. Particularly, nano spheres, nano wires, nanotubes , It has been remarked that it is possible to shorten the lithium diffusion distance to shorten the volume expansion by inducing alloying / de-alloying at the time of charging / discharging. However, many methods for synthesizing nanostructures are expensive raw materials, And a low yield of the active material.

Korean Patent Laid-Open No. 10-2008-0031323 (published on April 08, 2008). Korean Patent Publication No. 10-2008-0092283 (published on October 15, 2008). Korean Patent Publication No. 1020170104235 (Disclosure Date: Sep. 15, 2017)

The present invention relates to a method for producing a composite for a secondary battery anode active material having a high capacity as compared with a graphite anode material and an excellent cycle life as compared with a silicon anode material using an inexpensive raw material and a simple process as compared with the prior art, And an object of the present invention is to provide a negative electrode active material for a secondary battery.

According to an aspect of the present invention, there is provided a method of manufacturing a carbon nanotube, comprising: (a) mixing a soil containing iron (Fe) and an iron compound as main components and a carbon powder; And (b) complexing the soil with the carbon by applying mechanical energy to the mixed powder.

Also, the total weight of the iron atoms in the soil is 30 wt% or more based on the total weight of the soil.

Also, the iron (Fe) and iron compound-containing soil is one of red soil, laterite soil, and mixtures thereof.

The iron compound may be at least one selected from the group consisting of iron oxide, iron hydroxide, iron oxyhydroxide and iron silicide. Method.

Furthermore, by further containing the iron (Fe) and iron compound-containing soil is silica (SiO _2), alumina (Al ₂ O _3), magnesia (MgO) and titania, at least one selected from the group consisting of (TiO ₂₎ And a method for producing the composite.

In addition, the iron- and iron-compound containing soil includes FeO (OH) (iron (III) oxide-hydroxide), FeSi (Iron Silicide), FeSi ₂ (Iron disilicide) and SiO ₂ And a method for producing the composite.

The carbon may be one selected from the group consisting of acetylene black, Super P black, carbon black, Denka black, activated carbon, graphite, hard carbon and soft carbon. By weight of the total weight of the composite.

In the step (b), mechanical energy is applied by a vibratory-mill, a Z-mill, a planetary ball-mill, or an attrition-mill. To prepare a composite.

In another aspect of the present invention, the present invention provides a negative electrode active material for a secondary battery comprising the composite produced by the above production method.

The present invention further provides a lithium secondary battery including the negative electrode active material for a secondary battery according to another aspect of the present invention.

According to the present invention, a soil containing iron and iron compounds as main components such as red soil is combined with carbon through a high-energy mechanical milling process, and has a higher capacity than a conventional graphite-based anode material, The negative electrode active material for a secondary battery having an excellent life can be economically produced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart sequentially illustrating each step of the method for producing a composite according to the present invention. FIG.
2 shows the results of XRD analysis of the red soil used in the embodiment of the present invention.
FIG. 3 shows the results of the cycle life test of the lithium secondary battery including the red soil used as the negative electrode active material used in this embodiment.
4 shows the XRD analysis results of the red soil / carbon composite prepared in this Example.
FIG. 5 shows the results of the cycle life test of a lithium secondary battery including the red soil / carbon composite prepared in the present example as a negative electrode active material.
6 is a graph showing the relationship between the amount of lithium contained in the anode active material and the amount of lithium used as the cathode active material in the red soil, the red soil / C composite, and the graphite (MCMB) This is the experimental result of the cycle life of the secondary battery.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Embodiments in accordance with the concepts of the present invention can make various changes and have various forms, so that specific embodiments are illustrated in the drawings and described in detail in this specification or application. It should be understood, however, that the embodiments according to the concepts of the present invention are not intended to be limited to any particular mode of disclosure, but rather all variations, equivalents, and alternatives falling within the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms " comprises ", or " having ", or the like, specify that there is a stated feature, number, step, operation, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Hereinafter, the present invention will be described in detail.

The present invention relates to: As shown in FIG. 1, (a) mixing soil and carbon (C) powder containing iron (Fe) and an iron compound as a main component; And (b) combining the soil with the carbon by applying mechanical energy to the mixed powder.

In the step (a), the soil containing the iron (Fe) and the iron compound as the main component and the carbon (C) powder are mixed before the preparation of the composite.

Here, the fact that the soil contains iron (Fe) and iron compounds as a main component means that the total weight of the iron and iron compounds is not less than the weight of any other components contained in the soil.

Furthermore, it is preferable that the total weight of the iron atoms contained in the iron and iron oxides contained in the soil is 30 wt% or more of the total weight of the soil.

As described above, the soil containing iron (Fe) and iron compounds as main components or specific weight% or more can be carbonized and complexed to form a composite for a negative electrode active material for a secondary battery having a high capacity and an excellent cycle life.

Specific examples of the soil containing iron (Fe) and iron compounds as a main component include red soil, laterite soil, and a mixture thereof.

Red soil (red soil) refers to the soil bed developed under the broad-leaved forests in the subtropical Dow area. It is characterized by strong leaching of the base due to the leaching of the base and the accumulation of dioxides of iron or aluminum. Accumulation of humus Is known as a soil that does not cause the Pod soluning action.

Further, the laterite soil is a reddish brown soil widely distributed in the Savannah climatic zone, and is produced by the weathering of the surface and is produced mainly by the hydroxide of iron and aluminum, and the leaching action of the silicate powder or the base. It is difficult to farm, but it is used as building material in India. It is also called platyite, and is a gluing material produced as a weathered surface of the earth. It is mainly composed of hydroxides of iron and aluminum and is used for the dissolution of silicate particles or bases. Aluminum hydroxide in the latex concentrates to form bauxite, and iron hydroxide concentrates and becomes a calcite.

The iron compounds contained in the soil include iron oxides such as FeO, Fe ₂ O ₃ and Fe ₃ O ₄ , iron hydroxides such as Fe (OH) ₂ and Fe (OH) ₃ , Iron oxyhydroxide such as FeO (OH), iron silicide such as FeSi and FeSi _2, and the like, but the present invention is not limited thereto.

In addition, the soil may further contain various oxides which can be ordinarily included in the soil such as silica (SiO ₂ ), alumina (Al ₂ O ₃ ), magnesia (MgO), and titania (TiO ₂ ) have.

The mixing method of the iron / iron compound-containing soil and the carbon powder in this step is not particularly limited, and it is sufficient that the soil and the carbon powder can be uniformly mixed.

The carbon powder may be at least one selected from acetylene black, super P black, carbon black, Denka black, activated carbon, graphite, hard carbon or soft carbon. have.

Next, the step (b) is a step of producing a soil / carbon complex by complexing the soil with the carbon by applying mechanical energy to the mixed powder obtained in the previous step.

In this step, a method of applying mechanical energy to the mixed powder is not particularly limited, but it is preferable to use a high-energy ball milling which can more easily lead to the composite of the soil component and carbon.

Specifically, by applying mechanical energy to high-energy mechanical milling (HEMM) to a mixed powder containing iron / iron compound-containing soil and carbon powder, Carbon composite material.

For reference, high-energy ball milling can induce a chemical reaction in a reactant material by applying high energy through a high rotational force to the reactant material, as well as atomizing the powder and maximizing diffusion force between the powder particles.

The high-energy ball milling is used for high-energy ball milling such as a vibratory-mill, a Z-mill, a planetary ball-mill, and an attrition-mill. Of the ball milling device. For reference, in a typical high energy ball milling process, the temperature may rise to 200 DEG C during ball milling and the pressure may be on the order of 6 GPa.

According to the above-described composite manufacturing method, a soil containing iron and iron compounds as main components such as red soil is combined with carbon through a high-energy mechanical milling process, and a high-capacity silicon-based anode material The negative electrode active material for a secondary battery having an excellent cycle life can be produced economically.

Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

<Examples>

(1) Preparation of Red soil / carbon composite

In this example, red soil was used as a soil containing Fe and iron compounds for the production of the composite according to the present invention.

As a result of EDS (Energy Dispersive X-ray Spectroscopy) analysis on the used soil in this example, it was confirmed that the soil contained 43.26 wt% Fe, 42.75 wt% O, 8.22 wt% C, 5.77 wt% Si As shown in FIG. 2, it is confirmed that FeO (OH) (iron (III) oxide-hydroxide), FeSi (Iron Silicide), FeSi ₂ (Iron disilicide) and SiO ₂ .

FIG. 3 is a graph of a cycle life test result of a lithium secondary battery including a red earth metal used as a negative electrode active material used in the present embodiment. As shown in FIG. 3, the discharging capacity was significantly reduced to 33.4% after only 30 cycles (844 mAh / g → 282 mAh / g). Therefore, it was found that the performance was not enough to apply the anode active material alone.

Thus, in this embodiment, 3 g of mixed powder obtained by mixing the above-mentioned ground dust and carbon powder at a weight ratio of 7: 3, and steel balls are mixed at a weight ratio of 1:20 by weight of SKD11 material having a diameter of 5.5 cm and a height of 9 cm And then packed in a cylindrical vial, mounted on a vibrating mill (spex 8000), and subjected to high energy mechanical milling (HEMM) at a rotation speed of 900 rpm for 6 hours to obtain a red soil / carbon composite.

FIG. 4 is a result of XRD analysis of the red soil / carbon composite prepared in this Example. As shown in FIG. 4, the composite obtained in this Example contains Fe ₂ O ₃ and Fe ₃ O ₄ derived from iron and iron compounds in soil It has been confirmed that iron oxide is complexed with carbon.

(2) Evaluation of efficiency and cycle characteristics of the secondary battery including the red soil-carbon composite prepared in (1) as an anode active material

FIG. 5 is a graph of a cycle life test result of a lithium secondary battery including the red soil / carbon composite prepared in the present example as a negative electrode active material.

5, the discharge capacity was maintained close to 90% (745 mAh / g? 665 mAh / g) even after lapse of 100 cycles. Thus, the red soil / carbon composite according to the present Example can be applied as a negative electrode active material for a secondary battery Proved to be sufficient.

6 is a graph showing the results obtained by using the red soil used in the present embodiment, the red soil / C composite and the graphite (MCMB) produced in this embodiment as anode active materials This is the result of the comparison of the cycle life of the lithium secondary battery including the lithium secondary battery.

Referring to FIG. 6, the lithium secondary battery including the red soil / carbon composite according to the present embodiment as a negative electrode active material has much better cycle life than that of the red soil, and the meso-carbon microbeads, MCMB), it has been confirmed that it exhibits excellent lifespan characteristics maintaining the capacity of about 130% throughout the cycle range in which the present experiment is performed.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood. It is therefore to be understood that the above-described embodiments are illustrative and not restrictive in every respect.

Claims (10)

(a) mixing soil and carbon (C) powders containing iron (Fe) and iron compounds, wherein the total weight of iron atoms is at least 30 wt% based on the total weight of the soil; And
(b) combining the soil with the carbon by applying mechanical energy to the mixed powder,
The method of the soil composite, characterized in that FeO (OH), FeSi, jeokto containing FeSi ₂ and SiO ₂ (Red soil). delete delete delete The method according to claim 1,
Wherein the iron and iron compound-containing soil further comprises at least one selected from the group consisting of alumina (Al ₂ O ₃ ), magnesia (MgO) and titania (TiO ₂ ). delete The method according to claim 1,
The carbon may be one or more selected from the group consisting of acetylene black, Super P black, carbon black, Denka black, activated carbon, graphite, hard carbon and soft carbon &Lt; / RTI &gt; The method of claim 1,
Wherein mechanical energy is applied in a vibratory-mill, a Z-mill, a planetary ball-mill, or an attrition-mill in the step (b) &Lt; / RTI &gt; A negative electrode active material for a secondary battery comprising the composite produced by the method of any one of claims 1, 5, 7, and 8. 10. A lithium secondary battery comprising the negative electrode active material for a secondary battery according to claim 9.

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