KR101669316B1 - Sulfur-carbon composite and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a sulfur-carbon composite having uniform particle size and a method for producing the same, and it is possible to efficiently provide electron conductivity to sulfur and improve the capacity of the electrode because the particle size is uniform.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a sulfur-

The present application relates to sulfur-carbon composites and methods for their preparation.

The lithium-sulfur battery uses a sulfur-based compound having a sulfur-sulfur bond as a cathode active material and a carbon-based material in which an alkali metal such as lithium or a metal ion such as lithium ion is intercalated or deintercalated is used as a negative active material Battery. The reduction of the sulfur-sulfur bond during the reduction reaction leads to a decrease in the oxidation number of sulfur and an oxidation-reduction reaction in which the sulfur-sulfur bond is regenerated while the oxidation number of the sulfuric acid is increased .

The lithium-sulfur battery has an energy density of 3830 mAh / g when lithium metal is used as an anode active material, and an energy density of 1675 mAh / g when sulfur (S ₈ ) used as a cathode active material is used. . In addition, the sulfur compound used as the cathode active material is advantageous in that it is a cheap and environmentally friendly substance.

However, sulfur has an electric conductivity of 5 × 10 ^-30 S / cm, which is close to non-conducting, and thus there is a problem that electrons generated by the electrochemical reaction are difficult to migrate. Therefore, it has been necessary to use an electrically conductive material such as carbon which can provide a smooth electrochemical reaction site. In this case, when the conductive material and sulfur are used in a simple mixture, not only the life of the battery is deteriorated due to the leakage of sulfur into the electrolyte during the oxidation-reduction reaction, and when the appropriate electrolyte is not selected, lithium polysulfide, So that it is no longer possible to participate in the electrochemical reaction.

 Thus, there was a need to improve the mixing quality of carbon and sulfur to reduce the flux of sulfur into the electrolyte and to increase the electronic conductivity of the electrode containing sulfur.

Korean Patent Publication No. 10-2007-0083384

A problem to be solved by the present application is to provide a sulfur-carbon composite having a structure in which the particle size is uniform and carbon can efficiently impart conductivity to the inside and the outside of sulfur particles.

Another problem to be solved by the present application is to provide a method for producing the sulfur-carbon composite.

The problems to be solved by the present application are not limited to the above-mentioned technical problems, and other technical problems which are not mentioned can be clearly understood by those skilled in the art from the following description.

One embodiment of the present application is a sulfur-carbon composite comprising a sulfur particle or a sulfur particle including at least one carbon particle therein; And the carbon particles positioned on a part or the whole of the surface of the sulfur particle, wherein the d10 value is 0.1 to 1 times the d50 value based on the d50 value of the particle size distribution, and the d90 value is d50 Lt; RTI ID = 0.0 > 10-fold. ≪ / RTI >

Other embodiments of the present application include preparing and mixing sulfur powders and carbon powders having uniformly sized particles; Pressurizing the mixed powder to reduce voids between powders; And melting the mixed powder at the same time or after the pressurization to form a sulfur-carbon composite.

The sulfur-carbon composite according to one embodiment of the present application can impart conductivity to sulfur efficiently since the particle size is uniform. Accordingly, it is possible to reduce the outflow of sulfur into the electrolyte, increase the electron conductivity, and improve the capacity of the electrode.

FIG. 1 is a schematic diagram of a sulfur-carbon composite according to the size of a sulfur particle. FIG. 1 is a cross-sectional view of a structure in which carbon particles surround the surface of a sulfur particle. a represents the case where the diameter of the sulfur particles is 10 micrometers, and b represents the case where the diameter of the sulfur particles is 5 micrometers.
FIG. 2 is a schematic view of a sulfur-carbon composite when graphite is used as a carbon. FIG. 2 is a cross-sectional view of a structure in which carbon particles surround the surface of a sulfur particle. wherein a represents a sulfur-carbon composite having a structure in which graphite surrounds sulfur particles, b represents a structure in which graphite particles are enclosed within a sulfur particle and surrounds sulfur particles, and c represents a structure in which a gap between the sulfur- In the first embodiment.
FIG. 3 shows a process for producing a sulfur-carbon composite, wherein a represents a mixture of sulfur powder and carbon powder uniformly adjusted in particle size, b represents a pressurized state of the mixed powder, And the pressurized powder is melted.
FIG. 4 shows a scanning electron microscope (SEM) image of a structure in which carbon particles are wrapped around the outer surface of a sulfur particle in a state before dispersion into a ball mill in the sulfur-carbon composite material according to Example 1. FIG.
Fig. 5 is a further enlarged view of Fig.
6 is an SEM image of the sulfur-carbon composite according to Example 1 dispersed in a ball mill.
FIG. 7 shows a SEM image of a structure in which carbon particles are contained in the interior of the sulfur particles in the state before dispersion into a ball mill in the sulfur-carbon composite according to Example 2, and carbon particles are wrapped around the outer surface of the sulfur particles will be
8 is an SEM image of the sulfur-carbon composite according to Example 2 dispersed in a ball mill.
9 is an SEM image of the sulfur-carbon composite according to Comparative Example 1. Fig.
10 shows results of coin cell discharge tests for Example 1 and Comparative Example 1. Fig.

Brief Description of the Drawings The advantages and features of the present application, and how to accomplish them, will be apparent with reference to the embodiments described below in conjunction with the accompanying drawings. It should be understood, however, that this application is not limited to the illustrated embodiments but is to be accorded the widest scope consistent with the principles of the invention, Is provided to fully convey the scope of the invention to those skilled in the art, and this application is only defined by the scope of the claims. The dimensions and relative sizes of the components shown in the figures may be exaggerated for clarity of description.

Unless defined otherwise, all terms, including technical and scientific terms used herein, may be used in a manner that is commonly understood by one of ordinary skill in the art to which this application belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

Hereinafter, the present application will be described in detail.

One embodiment of the present application is a sulfur particle or a sulfur particle containing at least one carbon particle therein; And carbon particles located on a part or all of the surface of the sulfur particles.

One embodiment of the present application includes preparing and mixing (S 10) sulfur powders and carbon powders having uniformly controlled particle sizes; Reducing the gap between powders by pressurizing the mixed powder (S20); And a step (S30) of melting the mixed powder at the same time or after the pressurization to form a sulfur-carbon composite (S30).

One embodiment of the present application provides a sulfur-carbon composite produced according to the above process.

The sulfur-carbon composite improves the adhesion between sulfur and carbon in the composite and improves the adhesion between adjacent complexes, thereby enhancing the conductivity of the sulfur.

Conventionally, sulfur and porous carbon are mixed and heat treated to impregnate sulfur with carbon pores. In this case, sulfur should be impregnated into the pores of the carbon, but if the sulfur content exceeds the carbon impregnation range, And it is difficult to give electron conductivity to the sulfur so that it is restricted by the change of sulfur content.

However, according to one embodiment of the present application, the sulfur-carbon composite has a structure in which carbon particles are wrapped around the outer surface of the sulfur particles, or carbon particles are contained in the interior of the sulfur particles, it is advantageous that the conductive material, carbon, can effectively impart electron conductivity to sulfur.

In the sulfur-carbon composite according to one embodiment of the present application, the sulfur particles and the carbon particles are uniformly sized to uniformly control the size of the sulfur-carbon composite as a final product.

Conventional sulfur-carbon composites were prepared by mixing each material and physically sticking the carbon to a soft sulfur surface through a ball mill process. In this case, the ball milling time is long and the final product sulfur- There is a drawback that the composite particles are not uniform. If the particles are not uniform, there is a problem that the surface area per unit weight is not large and the electron conductivity of sulfur is poor.

However, the sulfur-carbon composite according to one embodiment of the present invention is prepared using sulfur particles uniformly controlled in size, and the size of the carbon particles is very small compared to the size of the sulfur particles. Therefore, The size of the particles is not largely deviated from the initial sulfur particle size, and the particle size becomes uniform. The more uniform the particle size, the greater the surface area per unit weight, the better the electron conductivity of the sulfur, the larger the capacity of the electrode, and the smaller the capacity loss.

The d10 value may be 0.1 to 1 times the d50 value, and the d90 value may be 1 to 10 times the d50 value, based on the d50 value of the particle size distribution. Specifically, the d10 value may be 0.2 to 1 times the d50 value, and the d90 value may be 1 to 3 times the d50 value. When it is within the above range, it can be said that the sulfur-carbon composite has a uniform particle size.

In the present specification, the "d number" of the particle size distribution means the maximum particle diameter when the particles distributed at various particle sizes are accumulated at the ratio of the numbers existing together with d. Specifically, d50 means the maximum particle diameter when particles having various particle sizes are accumulated up to 50% in a volume ratio. At this time, the diameter of the particles which is more than 0% but less than 50% of the total volume is less than or equal to d50. Also, d10 means the maximum particle diameter when particles having various particle sizes are accumulated up to 10% in a volume ratio. At this time, the diameter of particles corresponding to less than 10% of the total volume is less than or equal to d10. And, d90 means the maximum particle diameter when particles having various particle sizes are accumulated up to 90% in a volume ratio. At this time, the diameter of the particles corresponding to less than 90% of the total volume is less than or equal to d90. The effective particle size on the particle size distribution can be measured by conventional particle size measurement techniques well known to those skilled in the art. For example, by sedimentation field flow fractionation, photon correlation spectroscopy, light scattering (e.g. using Microtrac UPA 150), laser diffraction or disk centrifugation (disc centrifugation).

The d50 value of the sulfur-carbon composite particles is 1 micrometer to 30 micrometers, specifically 1 micrometer to 10 micrometers. Here, the d50 value of the sulfur particles may be 0.1 micrometer to 10 micrometers, and the size of the carbon particles may be smaller than the size of the sulfur particles.

When the size of the sulfur particles is larger than the above range, the wetting area with the electrolytic solution in the electrode and the reaction sites with lithium ions are reduced, and the amount of electrons transferred to the complex size is decreased, so that the reaction is delayed . So that the discharge capacity can be reduced. Therefore, the d50 value of the sulfur particles is 10 micrometers or less, so that the d50 value of the final sulfur-carbon composite particles is 30 micrometers or less, specifically 10 micrometers or less.

Also, the smaller the size of the sulfur particles, the smaller the size of the sulfur-carbon composite. As a result, the surface area per unit weight is increased, so that the electron conductivity of sulfur is also improved and the capacity of the electrode is increased. Therefore, the d50 value of the sulfur particles is 0.1 micrometer or more, and the d50 value of the final sulfur-carbon composite particles is 1 micrometer or more.

FIG. 1 is a schematic diagram of a sulfur-carbon composite according to the size of a sulfur particle. FIG. 1 is a cross-sectional view of a structure in which carbon particles surround the surface of a sulfur particle. a represents the case where the diameter of the sulfur particles is 10 micrometers, and b represents the case where the diameter of the sulfur particles is 5 micrometers.

FIG. 2 is a schematic view of a sulfur-carbon composite when graphite is used as a carbon. FIG. 2 is a cross-sectional view of a structure in which carbon particles surround the surface of a sulfur particle. a represents the sulfur-carbon composite having the structure in which the graphite particles surround the sulfur particles, b represents the structure in which the graphite particles are enclosed within the sulfur particles and surrounds the sulfur particles, and c represents the space between the sulfur- Is not formed.

In one embodiment of the present application, the tap density of the sulfur-carbon composite may be from 1 g / cc to 4 g / cc. If it is less than 1 g / cc, the thickness of the electrode may increase and the capacity may be decreased. In addition, the volume ratio of the electrode may be increased, so that the addition amount of the binder and the solvent may also increase. The effect is excellent when it is in the range of 1 g / cc to 4 g / cc.

In this specification, the tap density refers to the density when a particle-like object is filled in a container. The method for measuring the tap density may be any method as long as it measures the particle material in the container by repeating impact or vibration a predetermined number of times by tapping or shaking the container by a predetermined method predetermined.

In one embodiment of the present application, the carbon may be crystalline or amorphous carbon and may be conductive carbon. Specific examples of the carbon black include graphite, graphene, Super P, carbon black, denka black, acetylene black, ketjen black, channel black, perneic black, lamp black, Carbon nanotubes, carbon nanowires, carbon nanorings, carbon fabrics, and fullerenes (C60).

In one embodiment of the present application, the sulfur may be a sulfur element (S ₈ ) or a sulfur compound having an SS bond.

FIG. 3 shows a process for producing a sulfur-carbon composite, wherein a represents a mixture of sulfur powder and carbon powder uniformly adjusted in particle size, b represents a pressurized state of the mixed powder, And the pressurized powder is melted.

(S10) of preparing and mixing sulfur powder and carbon powder uniformly adjusted in particle size in the above-described method for producing a sulfur-carbon composite will be described.

The uniform size of the particles can be controlled using a wet ball mill or a dry jet mill method.

The step (S10) of preparing and mixing the sulfur powder and the carbon powder may further include dispersing the particles using an organic solvent after controlling the particle size before mixing. At this time, since the size-controlled sulfur particles may be partly aggregated, if the particles are swelled in an organic solvent, the aggregated particles may be loosened due to the repulsive force between the particles.

The organic solvent may be at least one selected from the group consisting of ethanol, toluene, benzene, N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), acetone, chloroform, dimethylformamide, cyclohexane, tetrahydrofuran and methylene chloride Can be used.

The mixing method may be carried out by putting it in a powder mixer for a predetermined time. The mixing time may be 10 minutes or more, 30 minutes or more, 10 hours or less, 5 hours or less, 2 hours or less.

The mixing ratio of the sulfur powder to the carbon powder may be 50 to 90:10 to 50 on a weight% basis. Therefore, the content ratio of sulfur and carbon in the final sulfur-carbon composite may be 50-90: 10-50 on a weight% basis. When the content of sulfur is less than 50% by weight, carbon particles other than carbon existing on the surface of the sulfur particles increase, and as the carbon content increases, the specific surface area increases and the amount of the binder added during the production of the slurry must be increased. The increase in the amount of the binder increases the sheet resistance of the electrode, and acts as an insulator to prevent electron transfer, which may degrade the cell performance. If the content of sulfur exceeds 90% by weight, the sulfur is molten and the sulfur which is not bonded with carbon becomes aggregated and becomes difficult to participate directly in the electrode reaction because it is difficult to receive electrons.

(S20) of reducing the voids between powders by pressurizing the mixed powder in the method for producing the sulfur-carbon composite will be described.

If the mixed powder is pressurized, the gap between the sulfur particles and the carbon particles can be reduced.

If the gap between the sulfur particles and the carbon particles is reduced by the pressing process, the sulfur particles may be melted through the melting process, thereby increasing the bonding force with the carbon particles.

If the pressure is not applied, even if the sulfur particles are melted, the sulfur-carbon composite structure in which the neighboring carbon particles are small in amount or the adhesion force between the carbon particles and the sulfur particles is weak, .

The pressure may be between ¹ kN / m ² and 50 kN / m ² . When the pressing pressure is less than 1 kN / m ² , the void between the sulfur particles and the carbon particles is not effectively reduced, so that the sulfur-carbon composite structure in which the carbon particles are wrapped around the sulfur particles may not be formed properly, / m preferably greater than ² days when losing the initial particle shape due to the ductility of sulfur can take place to the shape change of the hard plate-shaped or the like, applying a pressure of 1kN / m ² to 50 kN / m ^2.

At this time, the pressing time can be adjusted according to the content of the pressing equipment and the composite. For example, it may be more than 1 second, more than 5 seconds, less than 2 hours, less than 1 hour, less than 30 minutes, less than 1 minute, less than 30 seconds.

In step (S30), the sulfur-carbon composite material is formed by melting the mixed powder simultaneously with or after the pressurization in the above-described method for producing a sulfur-carbon composite material.

In the above step, the melting step may be carried out simultaneously with the pressurization, or may be carried out after the pressurization.

The melting temperature may be at least 115 캜, at least 130 캜, and at most 180 캜.

The melting time may be adjusted depending on the content of the complex, and may be, for example, 10 seconds or more, 30 seconds or more, 2 hours or less, 1 hour or less, 30 minutes or less, 10 minutes or less.

When the melting temperature is lower than 115 ° C, the sulfur particles are not melted, so that the carbon particles are wrapped around the sulfur particles or the sulfur-carbon composite structure in which the carbon particles are contained in the sulfur particles and the sulfur particles are wrapped May not be formed.

The method for producing a sulfur-carbon composite may further include dispersing the sulfur-carbon composite after the step (S30) of melting the mixed powder to form a sulfur-carbon composite.

At this time, the dispersion method can be carried out using a wet ball mill process.

One embodiment of the present application provides a cathode for a lithium-sulfur battery comprising the sulfur-carbon composite. The sulfur-carbon composite may be included in the anode as a cathode active material.

In addition to the positive electrode active material, the positive electrode may further include at least one additive selected from a transition metal element, a group IIIA element, a group IVA element, a sulfur compound of these elements, and an alloy of these elements and sulfur.

The transition metal element may be at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Hg and the like, and the Group IIIA element includes Al, Ga, In, and Ti, and the Group IVA element may include Ge, Sn, Pb, and the like.

The positive electrode may further include a positive electrode active material or, optionally, an additive, an electrically conductive conductive material for allowing electrons to smoothly move in the positive electrode, and a binder for adhering the positive electrode active material to the current collector.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, but may be a graphite based material such as KS6; Carbon black such as Super P, Super Black, Denka Black, Acetylene Black, Ketjen Black, Channel Black, Ferneic Black, Lamp Black, Summer Black and Carbon Black; Carbon derivatives such as carbon nanotubes and fullerene; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Or conductive polymers such as polyaniline, polythiophene, polyacetylene, and polypyrrole may be used alone or in combination.

The conductive material may be added in an amount of 0.01 wt% to 30 wt% based on the total weight of the mixture including the cathode active material.

Examples of the binder include poly (vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, alkylated polyethylene oxide, crosslinked polyethylene oxide, polyvinyl ether, poly (methyl methacrylate) (Trade name: Kynar), poly (ethyl acrylate), polytetrafluoroethylene polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, polystyrene, polyvinylidene fluoride, polyvinylidene fluoride, Derivatives thereof, blends, copolymers and the like can be used.

The content of the binder may be 0.5 to 30% by weight based on the total weight of the mixture containing the cathode active material. If the content of the binder is less than 0.5 wt%, the physical properties of the anode may be deteriorated and the active material and the conductive material may fall off. If the amount exceeds 30 wt%, the ratio of the active material and the conductive material is relatively decreased, can do.

The method for producing the positive electrode of the present application will be described in detail. First, the binder is dissolved in a solvent for preparing a slurry, and then the conductive material is dispersed. As the solvent for preparing the slurry, the cathode active material, the binder and the conductive material can be uniformly dispersed, and those which are easily evaporated are preferably used. Typical examples thereof include acetonitrile, methanol, ethanol, tetrahydrofuran, Propyl alcohol and the like can be used. Next, the cathode active material, or alternatively, together with the additive, is again uniformly dispersed in the solvent in which the conductive material is dispersed to prepare a cathode slurry. The amount of the solvent, the cathode active material, or optionally the additive contained in the slurry has no particular significance in the present application, and it is sufficient if it has an appropriate viscosity so as to facilitate coating of the slurry.

The slurry thus prepared is applied to a current collector, and vacuum dried to form a positive electrode. The slurry may be coated on the current collector with an appropriate thickness according to the viscosity of the slurry and the thickness of the anode to be formed.

The current collector generally has a thickness of 3 micrometers to 500 micrometers and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. More specifically, a conductive material such as stainless steel, aluminum, copper, or titanium may be used. More specifically, a carbon-coated aluminum current collector may be used. The use of a carbon-coated aluminum substrate is advantageous in that it has an excellent adhesion to an active material, has a low contact resistance, and can prevent corrosion caused by aluminum polysulfide, as compared with a carbon-coated aluminum substrate. The current collector may have various forms such as a film, a sheet, a foil, a net, a porous body, a foam or a nonwoven fabric

One embodiment of the present application relates to a positive electrode comprising the sulfur-carbon composite; cathode; And a separator disposed between the anode and the cathode.

The lithium-sulfur battery comprises: a cathode comprising the sulfur-carbon composite as a cathode active material; A negative electrode comprising lithium metal or a lithium alloy as a negative electrode active material; A separation membrane positioned between the anode and the cathode; And an electrolyte impregnated with the negative electrode, the positive electrode, and the separator, and including the lithium salt and the organic solvent.

The negative electrode may be a material capable of reversibly intercalating or deintercalating lithium ions as a negative electrode active material, a material capable of reversibly reacting with lithium ions to form a lithium-containing compound, a lithium metal or a lithium alloy .

The material capable of reversibly intercalating or deintercalating lithium ions may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof.

The material capable of reacting with the lithium ion to form a lithium-containing compound reversibly may be, for example, tin oxide, titanium nitrate, or silicon.

The lithium alloy may be, for example, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn.

The separation membrane located between the anode and the cathode may be made of a porous nonconductive or insulating material which separates or insulates the anode and the cathode from each other and enables transport of lithium ions between the anode and the cathode. Such a separation membrane may be an independent member such as a film, or may be a coating layer added to the anode and / or the cathode.

The material forming the separation membrane includes, for example, polyolefin such as polyethylene and polypropylene, glass fiber filter paper, and ceramic material, but is not limited thereto and may have a thickness of about 5 micrometers to about 50 micrometers, Micrometer to about 25 micrometers

The electrolyte impregnated into the negative electrode, the positive electrode and the separator includes a lithium salt and an organic solvent.

The concentration of the lithium salt may range from 0.2 M to 2 M, depending on various factors such as the precise composition of the electrolyte solvent mixture, the solubility of the salt, the conductivity of the dissolved salt, the charging and discharging conditions of the battery, , Specifically 0.6 M to 2 M, more specifically 0.7 M to 1.7 M. If it is used at less than 0.2 M, the conductivity of the electrolyte may be lowered and the performance of the electrolyte may be deteriorated. If it is used in excess of 2 M, the viscosity of the electrolyte may increase and the mobility of the lithium ion may be decreased. Lithium salt for example for use in the present application, LiSCN, LiBr, LiI, LiPF 6, LiBF 4, LiSO 3 CF 3, LiClO 4, LiSO 3 CH 3, LiB (Ph) 4, LiC (SO 2 CF 3) 3 and LiN (SO ₂ CF ₃₎ may include one or more from the group consisting of _2.

The organic solvent may be a single solvent or two or more mixed organic solvents. When two or more mixed organic solvents are used, it is preferable to use at least one solvent selected from two or more of the weak polar solvent group, the strong polar solvent group, and the lithium metal protective solvent group.

The weak polar solvent is defined as a solvent having a dielectric constant of less than 15 which is capable of dissolving a sulfur element in an aryl compound, a bicyclic ether, or a cyclic carbonate, and the strong polar solvent is a bicyclic carbonate, a sulfoxide compound, a lactone compound , A ketone compound, an ester compound, a sulfate compound, and a sulfite compound, wherein the lithium metal protective solvent is a saturated ether compound, an unsaturated ether compound, an N, Is defined as a solvent having a charge / discharge cycle efficiency of 50% or more to form a stable SEI (Solid Electrolyte Interface) on a lithium metal such as a heterocyclic compound containing O, S, or a combination thereof.

Specific examples of the weak polar solvent include xylene, dimethoxyethane, 2-methyltetrahydrofuran, diethyl carbonate, dimethyl carbonate, toluene, dimethyl ether, diethyl ether, diglyme or tetraglyme .

Specific examples of the strong polar solvent include hexamethyl phosphoric triamide,? -Butyrolactone, acetonitrile, ethylene carbonate, propylene carbonate, N-methylpyrrolidone, 3-methyl- Dimethyl formamide, sulfolane, dimethyl acetamide, dimethyl sulfoxide, dimethyl sulfate, ethylene glycol diacetate, dimethyl sulfite or ethylene glycol sulfite.

Specific examples of the lithium protecting solvent include tetrahydrofuran, ethylene oxide, dioxolane, 3,5-dimethylisoxazole, furan, 2-methylfuran, 1,4-oxane or 4-methyldioxolane.

One embodiment of the present application provides a battery module comprising the lithium-sulfur battery as a unit cell.

The battery module may be specifically used as a power source for an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

Hereinafter, the present invention will be described in detail by way of examples and comparative examples in order to specifically explain the present application. However, the embodiments according to the present application can be modified in various other forms, and the scope of the present application is not construed as being limited to the embodiments described below. Embodiments of the present application are provided to more fully describe the present application to those of ordinary skill in the art.

≪ Example 1 >

AGM-Flake (Mitsubishi, product name: SNG), which is a graphite powder with a particle size of less than 3 micrometers in average diameter and carbon powder, was mixed in a powder mixer for 1 hour and then placed in a bowl or mold for 10 seconds And a pressure of 10 kN / m ² was applied. The pressurized powder was melted on a hot plate at 130 DEG C for 1 minute to prepare a sulfur-carbon composite, which was then dispersed for 1 hour at 500 rpm in a wet ball mill.

FIG. 4 is a view showing a structure in which carbon particles are wrapped on the outer surface of a sulfur particle in a state before dispersion into a ball mill in the sulfur-carbon composite material according to Example 1. FIG. Fig. 5 is a further enlarged view of Fig.

Fig. 6 shows a sulfur-carbon composite according to Example 1. Fig. Referring to FIG. 6, it can be seen that the average diameter of the prepared sulfur-carbon composite is about 2 micrometers. In addition, it was confirmed that the sulfur-carbon composite according to Example 1 has a uniform size because the d50 value is 3 micrometers, the d10 value is 0.5 micrometer, and the d90 value is 15 micrometer.

≪ Example 2 >

Super P was added to the powder mixer with sulfur powder and carbon powder adjusted to an average diameter of 3 micrometers and mixed for 1 hour. The mixture was put into a bowl or a mold, and a pressure of 10 kN / m ² was applied for 10 seconds. The pressurized powder was melted on a hot plate at 130 DEG C for 1 minute to prepare a sulfur-carbon composite, which was then dispersed for 1 hour at 500 rpm in a wet ball mill.

7 is a SEM image of a sulfur-carbon composite according to Example 2 before being dispersed in a ball mill, wherein carbon particles are contained in the interior of the sulfur particles and not only the carbon particles surround the outer surface of the sulfur particles, It can be confirmed that it is contained in the inside of the particle.

8 is a SEM image of the sulfur-carbon composite according to Example 2 dispersed in a ball mill. It can be seen that the average diameter of the sulfur-carbon composite prepared is about 3 micrometers. In addition, the sulfur-carbon composite according to Example 2 had a d50 value of 3 micrometers, a d10 value of 1 micrometer, and a d90 value of 10 micrometers.

≪ Comparative Example 1 &

Sulfur powder and AGM-Flake carbon powder, which were not controlled in particle size, were mixed in a powder mixer for 1 hour and then dispersed at 500 rpm for 1 hour in a wet ball mill to prepare a sulfur-carbon composite.

Fig. 9 shows a sulfur-carbon composite according to Comparative Example 1. Fig. 11, it can be confirmed that the diameter of the sulfur particles is not uniform.

<Test Example>

70 wt% of the sulfur-carbon composite prepared in Example 1 and Comparative Example 1 was used as a positive electrode active material, 20 wt% of denka-black as a conductive material, 10 wt% of PVDF as a binder was dissolved in a solvent NMP (N-methyl-2-pyrrolidone) to prepare a positive electrode slurry and then coated on an aluminum current collector to prepare a positive electrode. A lithium foil having a thickness of about 150 micrometers was used as a negative electrode and a mixed electrolyte of dimethoxyethane and dioxolane (5: 4 by volume) in which 1 M LiN (CF ₃ SO ₂ ) ₂ was dissolved as an electrolyte was used. Molecular polyolefin was used to prepare a lithium-sulfur battery coin cell.

The results of the test at a rate of 0.1 C using a charge / discharge device are shown in FIG. 10 shows that the lithium-sulfur battery using the composite prepared in such a manner that the carbon particles surround the sulfur particles in Example 1 has a higher discharge capacity than the lithium-sulfur battery using the composite produced by the simple ball milling method in Comparative Example 1 I could.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. It is therefore to be understood that the above-described embodiments are illustrative and non-restrictive in every respect.

Claims (19)

delete delete delete delete delete delete delete delete Preparing and mixing a sulfur powder and a carbon powder uniformly adjusted in particle size;
Pressurizing the mixed powder to reduce voids between powders;
Melting the mixed powder at the same time or after the pressurization to form a sulfur-carbon composite; And
And dispersing the sulfur-carbon composite,
Wherein the d10 value is 0.1 to 1 times the d50 value and the d90 value is 1 to 10 times the d50 value based on the d50 value of the particle size distribution of the sulfur-carbon composite. delete The method of claim 9,
Wherein the mixing ratio of the sulfur powder to the carbon powder is 50 to 90: 10 to 50 by weight. The method of claim 9,
Wherein said sulfur-carbon composite has a tap density of 1 g / cc to 4 g / cc. The method of claim 9,
Wherein the d50 value of the sulfur-carbon composite particles is 1 micrometer to 30 micrometers. The method of claim 9,
The d50 value of the sulfur powder particles is 0.1 micrometer to 10 micrometers,
Wherein the size of the carbon powder particles is smaller than the size of the sulfur powder particles. The method of claim 9,
Wherein the particle size is uniformly controlled by using a wet ball mill or a dry jet mill method. The method of claim 9,
The method of preparing and mixing the sulfur powder and the carbon powder further comprises dispersing the sulfur powder and the carbon powder using an organic solvent after controlling the size of the particles. 18. The method of claim 16,
The organic solvent may be at least one selected from the group consisting of ethanol, toluene, benzene, N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), acetone, chloroform, dimethylformamide, cyclohexane, tetrahydrofuran and methylene chloride Carbon composite material according to claim 1, The method of claim 9,
Wherein the pressing pressure is 1 kN / m ² to 50 kN / m ² . The method of claim 9,
Wherein the melting temperature is 115 ° C or higher.

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