KR20170095622A - Method of making graphite for battery anode material using microwave - Google Patents

Abstract

The present invention relates to a method for producing graphite, comprising the following steps: preparing carbon powder; mixing carbon powder and metal particles, so as to prepare a carbon-metal mixture; applying microwave to the carbon-metal mixture so as to acquire graphite-metal mixture; removing metal from the graphite-metal mixture so as to obtain graphite; and conducting reduction with graphite. In addition, the method for producing graphite further comprises the following steps: preparing a mixture of metal particles and carbon powder; applying microwave to the mixture so as to acquire graphite; and removing residual metal through acid treatment to graphite. Through the graphite production method using microwave, it is possible to obtain graphite for battery negative electrode materials from amorphous carbon.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing graphite for battery cathodes using a microwave,

The present invention relates to a method for producing graphite for battery cathodes from amorphous carbon using microwaves.

Graphite is the most commonly used anode material for commercial batteries, and is in a very important position in the battery and energy storage sectors. However, natural graphite is classified as a Supply Risk Material due to the continuous increase in demand.

Artificial graphite is produced through a graphitization process in which a carbon material is heat-treated at 3000 ° C. In an electric furnace, which is generally used, the atmosphere inside the reactor must be heated first. Since slow conduction and convection are utilized, There is a waste of time. Therefore, there is a need for a graphite manufacturing method having alternative and efficient properties of battery cathodes.

Korea Patent Publication No. 2010-0122082

It is an object of the present invention to provide a method for producing graphite having battery anode characteristics from amorphous carbon using microwaves.

It is an object of the present invention to provide a method for producing a graphite-metal composite, which comprises the steps of: providing a carbon powder; preparing a carbon-metal mixture by mixing metal particles with carbon powder; Removing the metal from the mixture to obtain graphite, and reducing the graphite.

The carbon powder may contain activated carbon.

The metal may comprise a transition metal.

The transition metal may include at least one of nickel, copper, cobalt and iron.

The carbon-metal mixture may be prepared by mixing the carbon powder and the metal in a liquid phase.

And drying the mixed carbon-metal mixture in the liquid phase.

The metal may be obtained from a metal halide, and the metal halide may include at least one of nickel chloride, copper chloride and iron chloride.

The metal may be obtained from a metal acetate, and the metal acetate may include one or more of nickel acetate, copper acetate and iron acetate.

The microwave can be applied in an inert gas atmosphere.

Metal removal can be performed using an acid solution.

The acid solution may comprise hydrochloric acid.

The reduction reaction can be performed using hydrogen.

It is still another object of the present invention to provide a graphite manufacturing method which comprises the steps of: providing a mixture of carbon powder and metal particles; adding graphite to the mixture by microwaving; and removing graphite by acid treatment to remove the remaining metal Lt; / RTI >

The mixture of the carbon powder and the metal particles may be mixed in a liquid phase, and may be further dried after mixing.

Acid treatment can be done with hydrochloric acid.

And reducing the graphite from which the residual metal has been removed.

The reduction reaction can be performed using hydrogen.

The metal particles are characterized by being obtained from a transition metal, and the transition metal may include at least one of nickel, copper, cobalt and iron.

The metal particles may be obtained from at least one of a metal halide and a metal acetate, and the metal halide may include at least one of nickel chloride, copper chloride and iron chloride, and the metal acetate may be at least one of nickel acetate, copper acetate and iron acetate And may include one or more.

According to the present invention, graphite having battery anode characteristics can be produced from amorphous carbon by using microwave.

1 is a graphite powder (MSP-MW) obtained by microwave reaction after impregnating carbon powder (MSP20) before microwave reaction, MSP20 and nickel acetate, and graphite powder (MSP- MSP20-Acid) and MSP20-Acid were subjected to reduction treatment under a hydrogen atmosphere to give X-ray diffraction analysis of graphite powder (MSP20-Reduc).
2 is a graph showing Raman spectroscopic results of graphite powder (MSP20-Reduc) subjected to microwave reaction, acid solution treatment and reduction treatment after impregnating MSP20 with nickel acetate before microwave reaction.
3 shows the differential charge capacity (dQ / dV plot) of graphite powder (MSP20-Reduc) subjected to microwave reaction before carbon powder (MSP20) and MSP20 with impregnation with nickel acetate, microwave reaction, acid solution treatment and reduction treatment )to be.
4 is a discharge potential profile of carbon powder (MSP20) before microwave reaction and graphite powder (MSP20-Reduc) after impregnation of MSP20 with nickel acetate, microwave reaction, acid solution treatment and reduction treatment .
5 is a cycle performance of graphite powder (MSP20-Reduc) subjected to microwave reaction before carbon powder (MSP20), MSP20 impregnated with nickel acetate, microwave reaction, acid solution treatment and reduction treatment.
6 shows the C-rate performance of graphite powder (MSP20-Reduc) subjected to microwave reaction before carbon powder (MSP20) and MSP20 with nickel acetate impregnation, microwave reaction, acid solution treatment and reduction treatment, to be.

In the present invention, carbon is mixed with a metal, followed by graphitization of carbon using a microwave, and an acid solution treatment and reduction treatment are performed to produce graphite having battery anode characteristics.

The 'mixing' here includes chemical bonding as well as simple physical mixing.

Microwave is characterized by its fast reaction rate because it can directly transfer energy to a desired substance without going through the medium. However, since the microwave has a limited range of penetration into the carbon, the carbon as the raw material can be provided in powder form.

Metals are characterized by their high electrical conductivity, which means that when irradiating microwaves, energy is concentrated on the surface and reflected or instantaneously brought to high temperatures.

In addition, metals such as iron and nickel serve to crystallize carbon at a relatively low temperature through catalysis. Therefore, when microwave is applied after mixing carbon powder and metal, graphitization can be achieved in a short time at a lower temperature than the existing graphitization process.

The metal can be used without restrictions as long as it is a metal capable of converting amorphous carbon into crystalline graphite through catalytic graphitization.

The metal may be a transition metal, and may be any one of iron, copper, cobalt, and nickel. Further, the metal may be obtained from a metal precursor, and may be obtained from at least one of a metal halide and a metal acetate. In addition, the metal halide may include at least one of nickel chloride, copper chloride, and iron chloride, and the metal acetate may include at least one of nickel acetate, copper acetate, and iron acetate.

A mixture of carbon and metal can be obtained by stirring carbon powder and metal powder. However, the present invention is not limited to this, and if the carbon and the metal can be mixed well, it may be a form other than the powder, or a mixing method other than stirring may be possible.

When the pore volume of the carbon powder is large, the metal may be uniformly distributed when the carbon powder is stirred with the metal. Therefore, the carbon powder can be used as a powder of activated carbon having a large surface area, and other embodiments are possible as far as the carbon powder is capable of uniformly distributing the metal during stirring.

When nickel acetate is used as the metal source, the graphite manufacturing method will be described.

Carbon powder and nickel acetate are stirred in an aqueous solution to make a carbon-nickel mixture and then the carbon-nickel mixture is dried. At this time, when the carbon-nickel mixture is not dried, liquid may remain in the mixture, so undesired reactions may occur and microwave reaction efficiency may be lowered.

When microwave is applied to the powder of the obtained carbon-nickel mixture, graphite is obtained. The obtained graphite may be in powder form and may contain a trace amount of nickel. The microwave serves to make the carbon-nickel mixture into an inert gas atmosphere.

The remaining trace amount of nickel after the reaction can be removed by treatment with an acid solution, and the acid solution used may be hydrochloric acid, but is not limited thereto.

The carbon-nickel mixture treated with the acid solution then undergoes a reduction reaction in order to remove functional groups which may occur during the acid solution treatment. At this time, the reduction reaction may be a reduction reaction using hydrogen, but is not limited thereto.

Hereinafter, a method for producing graphite for a battery anode using microwaves will be described in detail with reference to examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited by the following examples.

<Experimental Example>

Graphite manufacture

a) nickel acetate impregnation

Six millimoles of nickel acetate per gram of MSP20, a kind of activated carbon powder, was mixed with ethanol and stirred at room temperature for 12 hours or more. The carbon-metal mixture in which all of the ethanol evaporated was dried in an oven at 75 DEG C for 24 hours. By drying, the carbon-metal mixture became powder again.

b) microwave reaction

The powder of the carbon-metal mixture obtained above was placed in a quartz tube to conduct microwave reaction to obtain graphite. 2.45 GHz microwave was irradiated for 5 minutes at 1500 W power. Argon was flowed at 100 sccm before the reaction and during the reaction to block the reaction with oxygen. The graphite (MSP20-MW) was taken out after allowing the argon to flow at an ordinary temperature after the reaction. The obtained graphite is in powder form.

c) Remaining Nickel Removal and Reduction

The nickel remaining on the graphite obtained above was removed using hydrochloric acid. The graphite obtained above was added to 1M hydrochloric acid solution and stirred for 12 hours (600 rpm, 75 ° C), filtered and dried to obtain graphite powder (MSP20-Acid) from which nickel was removed. Thereafter, a graphite powder (MSP20-Reduc) was obtained in which a functional group generated during the hydrochloric acid treatment was removed by a reduction reaction in a hydrogen atmosphere (500 sccm of argon and 200 sccm of hydrogen) for 30 minutes in a 900 ° C. furnace.

d) Evaluation of secondary battery anode characteristics

For comparison with the MSP20-Reduc sample, an electrode using MSP20 sample was prepared. Each electrode is manufactured by mixing active material: carbon black: polyvinylidene difluoride in a mass ratio of 8: 1: 1, and then using N-methyl-2-pyrrolidone as a solvent to prepare a slurry . The slurry is applied on a copper collector, dried in an oven at 60 ° C and completely dried in a vacuum oven at 110 ° C. The dried electrode is cut into a round shape and charged into a lithium secondary battery cell. Lithium metal is used as a counter electrode, ethylene carbonate / dimethyl carbonate (1: 1 volume ratio) solution in which 1.0 M lithium hexafluorophosphate salt is dissolved, and propylene carbonate electrolyte in which 1.0 M lithium perchlorate salt is dissolved. A CR2032 lithium ion battery is manufactured inside a glove box with oxygen and moisture blocking. The completed battery was subjected to constant current charging and discharging by flowing various current densities.

X-ray diffraction spectroscopy

1 is a graphite powder (MSP20-MW, mustard solid line) obtained by microwave reaction after impregnating carbon powder (MSP20, gray solid line) before microwave reaction, graphite powder MSP20-Acid, solid orange line) and graphite powder (MSP20-Reduc, red solid line) with the functional groups removed during hydrochloric acid treatment through hydrogen reduction reaction.

The results of the X-ray diffraction analysis of FIG. 1 show that, when compared with the MSP20 graph, the (002) peak near 26 °, which is used as an index of graphitization after the microwave reaction after impregnation with nickel acetate, (MSP20-MW, MSP20-Acid, and MSP20-Reduc). In addition, the MSP20-Acid graph shows that the remaining nickel (the portion indicated by the black diamond of MSP20-MW) after the microwave reaction disappears mostly during the acid treatment.

Table 1 shows the position of the (002) peak per sample and the interlayer distance (d ₀₀₂ ) converted by Bragg's law. As can be seen in Table 1, the position of the (002) peak generated by the microwave treatment and the inter-layer distance are almost similar to those of the commercial graphite, and it is confirmed that the structure is well maintained without significant change in acid treatment and hydrogen reduction reaction .

Therefore, according to the present invention, it is possible to obtain graphite having a quality similar to that of commercial graphite by microwave heating.

Raman spectroscopy analysis

FIG. 2 shows structural changes of carbon powder through Raman spectroscopy. The most characteristic Raman peak of the carbon material is the D-band (1350 cm ^-1 ) observed in the unaligned structure with the G-band (1582 cm ^-1 ) observed on the well aligned graphite side. The larger the intensity ratio (I _G / I _D ) of these two bands, the better the alignment of the graphite.

In FIG. 2, the gray solid line is the analysis result of MSP20 and the solid red line is the analysis result of MSP20-Reduc.

In this experiment, I _G / I _D of carbon powder increased remarkably from 1.07 before microwave reaction to 1.89 after microwave reaction. In addition, MSP20-Reduc can be used to identify 2D peaks and 2D peaks found in highly crystalline graphite that could not be seen in MSP20. Therefore, according to the present invention, graphite having high crystallinity can be obtained through microwave heating.

battery Negative electrode material  Character analysis

3 is a differential charge capacity chart (dQ / dV plot) of a battery using MSP20 and MSP20-Reduc as cathode materials, respectively. Unlike MSP20, where the oxidation-reduction reaction occurs over a wide range, MSP20-Reduc shows a typical crystalline graphite battery characteristic with a concentration of 0.21V. It was confirmed electrochemically that graphitization using microwave was effective.

4 is a discharge potential profile of a battery using MSP20 and MSP20-Reduc as cathode materials, respectively. The discharge potential curve was measured using a 1 M LiClO ₄ and propylene carbonate (PC) electrolyte. In MSP20-Reduc, unlike MSP20, a long horizon appears from near 1V, which is similar to the graphite cathode shown in the previously reported polycarbonate electrolyte. Thus, the results of FIG. 4 also confirmed electrochemically that graphitization occurred effectively.

5 shows the result of measurement of the battery cycle performance of the battery using MSP20 and MSP20-Reduc as cathode materials, respectively. Cells made from both samples were activated for 4 cycles at 0.2C rate and then characterized at 1C rate. MSP20-Reduc is a negative electrode, the maximum capacity is 321 mA hg ^-1 , and the capacity is stable even over 300 cycles. On the other hand, in the case of a battery made of cathode material of MSP20, the capacity corresponding to half of the maximum capacity is shown in the 300th cycle. Therefore, in the carbon powder subjected to the microwave graphitization, it was confirmed that the capacity and the stable performance of the battery as a negative electrode material were higher.

FIG. 6 shows the C-rate performance (C-rate performance) of a battery using MSP20 and MSP20-Reduc as cathode materials, respectively. At a rate of 1C or higher, MSP20-Reduc shows higher capacity than MSP20. Therefore, it can be said that the battery using the carbon powder having the microwave graphitization as the negative electrode shows excellent characteristics even in the high-speed charging / discharging environment.

Claims (19)

Providing a carbon powder;
Mixing the carbon particles with metal particles to prepare a carbon-metal mixture;
Adding microwave to the carbon-metal mixture to obtain a graphite-metal mixture;
Removing the metal from the graphite-metal mixture to obtain graphite; and
Reducing the graphite;
&Lt; / RTI &gt; The method according to claim 1,
Wherein the carbon powder comprises activated carbon. The method according to claim 1,
Wherein the metal comprises a transition metal. The method of claim 3,
Wherein the transition metal comprises at least one of nickel, copper, cobalt and iron. The method according to claim 1,
Wherein the carbon-metal mixture is prepared by mixing the carbon powder and the metal in a liquid phase. 6. The method of claim 5,
Drying the mixed carbon-metal mixture in the liquid phase;
Further comprising the steps of: 6. The method of claim 5,
Characterized in that the metal is obtained from a metal halide,
Wherein the metal halide comprises at least one of nickel chloride, copper chloride and iron chloride. 6. The method of claim 5,
Characterized in that the metal is obtained from a metal acetate,
Wherein the metal acetate comprises at least one of nickel acetate, copper acetate, and iron acetate. The method according to claim 1,
Wherein the microwave is applied in an inert gas atmosphere. The method according to claim 1,
Wherein the metal removal is carried out using an acid solution. 11. The method of claim 10,
Wherein the acid solution comprises hydrochloric acid. The method according to claim 1,
Wherein the reduction reaction is carried out using hydrogen. Providing a mixture of carbon powder and metal particles;
Adding microwave to the mixture to obtain graphite;
Removing the remaining metal by acid treatment on the graphite;
&Lt; / RTI &gt; 14. The method of claim 13,
Wherein the mixture of the carbon powder and the metal particles is mixed in a liquid phase,
Drying after mixing;
Further comprising the steps of: 14. The method of claim 13,
Wherein the acid treatment is carried out with hydrochloric acid. 14. The method of claim 13,
Reducing the graphite from which the residual metal has been removed;
Further comprising the steps of: 17. The method of claim 16,
Wherein the reduction reaction is carried out using hydrogen. 15. The method of claim 14,
Wherein the metal particles are obtained from a transition metal,
Wherein the transition metal comprises at least one of nickel, copper, cobalt and iron. 15. The method of claim 14,
Wherein the metal particles are obtained from at least one of a metal halide and a metal acetate,
Wherein the metal halide comprises at least one of nickel chloride, copper chloride and iron chloride,
Wherein the metal acetate comprises at least one of nickel acetate, copper acetate, and iron acetate.

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