KR101587324B1 - Sulfur-carbon composite and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a sulfur-carbon composite material and a method of manufacturing the same. The sulfur-carbon composite material according to the present application has uniform particle size and shape, and can thus impart conductivity to sulfur efficiently. Performance can be improved.

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

The problem to be solved by the present application is to provide a method for producing 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 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 relates to a method for preparing a solution, comprising: dispersing sulfur and carbon in an organic solvent to obtain a solution; Heating the solution to melt and mix the sulfur to form a sulfur-carbon composite; And cooling the solution while stirring to adjust the particle size of the sulfur-carbon composite.

Another embodiment of the present application is a sulfur-carbon composite comprising: a sulfur particle having at least one carbon particle therein; Carbon composite particles having a diameter of not less than 0.1 micrometer and not more than 10 micrometers, wherein the diameter of the carbon particles in the sulfur-carbon composite particle Provides a sulfur-carbon composite of less than 100 nanometers.

Another embodiment of the present application provides a positive electrode for a lithium-sulfur battery comprising the sulfur-carbon composite.

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

Another embodiment of the present application provides a battery module including the lithium-sulfur battery as a unit battery.

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

1 shows a cross section of a sulfur-carbon composite particle according to one embodiment of the present application. In FIG. 1, reference numeral 100 denotes a sulfur-carbon composite, reference numeral 10 denotes sulfur particles, and reference numeral 20 denotes carbon particles.
2 shows a process for producing a sulfur-carbon composite according to one embodiment of the present application.
FIG. 3 is a scanning electron microscope (SEM) image of the sulfur-carbon composite prepared according to Example 1. FIG.
4 is an enlarged view of the image of Fig.
5 shows an SEM image of the sulfur-carbon composite prepared according to Example 2. Fig.
6 is an SEM image of the sulfur-carbon composite prepared according to Example 3. Fig.
Fig. 7 is an enlarged view of the image of Fig.
8 is an SEM image of the sulfur-carbon composite prepared according to Example 4. Fig.
9 is an SEM image of the sulfur-carbon composite prepared according to Comparative Example 1. Fig.
10 is an SEM image of a sulfur-carbon composite prepared according to Comparative Example 2. [Fig.
FIG. 11 shows the results of measurement of the charge-discharge characteristics of a lithium-sulfur battery coin cell manufactured by applying Example 1. FIG.
FIG. 12 shows the results of measurement of charge-discharge characteristics of a lithium-sulfur battery coin cell manufactured by applying 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. The present application, however, is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles of the invention as defined in the appended claims. 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 includes a step (S10) of dispersing sulfur and carbon in an organic solvent to obtain a solution; Heating the solution to melt and mix sulfur to form a sulfur-carbon composite (S20); And cooling the solution while stirring to adjust the particle size of the sulfur-carbon composite (S30).

The method for preparing a sulfur-carbon composite according to one embodiment of the present application includes the step of adjusting the particle size of the sulfur-carbon composite (S30), washing and drying the organic solvent to obtain a sulfur-carbon composite powder (S40).

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

One embodiment of the present application is a sulfur-carbon composite comprising: a sulfur particle having at least one carbon particle therein; Carbon composite particles having a diameter of not less than 0.1 micrometer and not more than 10 micrometers, wherein the diameter of the carbon particles in the sulfur-carbon composite particle Provides a sulfur-carbon composite of less than 100 nanometers.

1 shows a cross section of a sulfur-carbon composite particle according to one embodiment of the present application. In FIG. 1, reference numeral 100 denotes a sulfur-carbon composite, reference numeral 10 denotes sulfur particles, and reference numeral 20 denotes carbon particles.

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.

As another method of the prior art, a method of mixing sulfur powder and carbon powder and ball milling to prepare a sulfur-carbon composite material is used. In this case, the manufacturing method is simple, but it is difficult to control the size and shape of the composite material uniformly there was.

However, the sulfur-carbon composite produced by the manufacturing method according to one embodiment of the present application has a structure in which carbon particles are contained inside and outside the sulfur particles, so that sulfur and carbon can be mixed at a uniform ratio, Carbon has the advantage that it can effectively impart electron conductivity to sulfur.

2 shows a process for producing a sulfur-carbon composite according to one embodiment of the present application.

In the above-mentioned production method, a state (S10) of obtaining a solution by dispersing sulfur and carbon in an organic solvent is as follows.

The sulfur particles and the carbon particles must be dispersed and reacted in order to uniformly contact the sulfur particles with the carbon particles, and thereby the electric conductivity of the non-conductive sulfur can be improved. Therefore, it is preferable to disperse the sulfur particles using an organic solvent.

In one embodiment of the present application, the organic solvent may be a polar organic solvent having a boiling point of 150 ° C or higher. Specifically, dimethyl sulfoxide (150 ° C), isoamyl propionate (156 ° C), ethyl lactate 2-heptanone (150 占 폚), 2-methyl-3-heptanone (159 占 폚), ethyl-2-hydroxynaphthalene (156 占 폚), ethyl methoxyacetate Methoxypropionate (158 占 폚), 2-methoxyethyl ether (162 占 폚), 3 占 폚 -methoxybutyl acetate (170 占 폚), 2- Propanol (161 占 폚), diethylene glycol dodecyl ether (169 占 폚), dipropylene glycol methyl ether (188 占 폚), 2-butoxyethanol (171 占 폚) Octanone (168 占 폚), 3-nonanone (188 占 폚), 5-nonanone (187 占 폚) Methyl-2-pentanone (166 占 폚), 2-methylcyclohexanone (163 占 폚), 3-methylcyclohexane (170 DEG C), 4-methylcyclohexanone (170 DEG C), 2,6-dimethylcyclohexanone (175 DEG C), 2,2,6-trimethylcyclohexanone (179 DEG C), cycloheptanone ), Ethyl acetate (169 占 폚), amyl butyrate (185 占 폚), isopropyl lactate (167 占 폚), butyl lactate (186 占 폚), ethyl 3-hydroxybutyrate Propoxy) propionate (170 DEG C), ethyl-3-hydroxybutyrate (180 DEG C), propyl- 170 DEG C), propylene glycol methyl ether propionate (160 DEG C), diethylene glycol dimethyl ether (162 DEG C), diethylene glycol dimethyl ether acetate (165 DEG C), dipropylene glycol methyl ether (188 DEG C) Dimethyl ether (171 C), ethylene glycol butyl ether (171 C), diethylene glycol methyl ethyl ether (176 C), diethylene glycol methyl iso Ethyl 3-ethoxypropionate (170 占 폚), diethylene glycol monomethyl ether (194 占 폚), 4-ethylhexyl methacrylate (179 占 폚), ethylene glycol diethyl ether Diethyleneglycol monoethyl ether (202 占 폚), butyrolactone (204 占 폚), hexylbutylate (205 占 폚), di N-methyl-2-pyrrolidone (212 占 폚), tripropyl glycol dimethyl ether (215 占 폚), triethylene glycol dimethyl ether (219 占 폚), ethylene glycol methyl ether acetate (209 占 폚), diethylene glycol butyl methyl ether (216 DEG C), diethylene glycol ethyl ether acetate (217 DEG C), diethylene glycol butyl ether acetate (245 DEG C), 3-epoxy-1,2-propanediol (222 DEG C) ), Diethylene glycol monobutyl ether (231 占 폚), tripropyl glycol methyl ether (242 占 폚), diethylene glycol (245 占 폚), 2- Diethylene glycol dibutyl ether (256 占 폚), triethylene glycol ethyl ether (256 占 폚), diethylene glycol dibutyl ether (25 占 폚), diethylene glycol dibutyl ether Ethylene glycol monohexyl ether (260 占 폚), triethylene glycol butyl methyl ether (261 占 폚), triethylene glycol butyl ether (271 占 폚), tripropyl glycol (273 占 폚), and tetraethylene glycol dimethyl ether Or one or more selected from the group consisting of In the above-mentioned specific organic solvent type, the portion indicated by parentheses means the boiling point of the solvent.

The content of the organic solvent in the carbon solution may be 500 times or more and 2,000 times or less the weight of the carbon. The content of the solvent should be at least 500 times as much as the weight of carbon, so that the carbon particles can be dispersed evenly in the solvent. If the amount is less than 2000 times, the solubility of the sulfur particles is not excessively increased, and the yield of the final product can be prevented from being lowered.

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 (C ₆₀ ).

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

The step (S20) of heating the solution to melt and mix sulfur to form a sulfur-carbon composite will now be described.

The heating temperature may be any temperature at which sulfur is melted. Specifically, the heating temperature may be 120 ° C or higher, 150 ° C or higher, and 180 ° C or lower. If the heating temperature is lower than 120 ° C, the sulfur particles may not be melted and the sulfur-carbon composite structure may not be properly formed. If the heating temperature is higher than 180 ° C, the organic solvent may evaporate during the reaction time.

The heating time can be adjusted according to the content of sulfur, specifically, it may be 10 minutes or more, and may be 30 minutes or less.

The mixing method may be carried out, for example, by stirring for a certain period of time, but is not limited thereto. At this time, the mixing time may be 10 minutes or more and 30 minutes or less. At this time, when mixing by stirring, the speed may be 500 rpm or more and 10,000 rpm or less.

The step (S30) of controlling the particle size of the sulfur-carbon composite by cooling the mixture solution while stirring is explained as follows.

The stirring may be performed by adding water to the mixture solution. In this case, the weight ratio of water to organic solvent in the mixture solution may be 5: 1 to 1: 2. The weight of water should be at least 0.5 times the weight of the organic solvent so that recrystallization may occur during cooling.

The stirring speed may be specifically 500 rpm or more, more specifically 1,000 rpm or more, specifically 10,000 rpm or less, more specifically 3,000 rpm or less. The size of the sulfur-carbon composite particles formed according to the stirring speed may be varied. The larger the stirring speed, the smaller the particle size, and the smaller the particle size, the larger the particle size.

The stirring time may be 10 minutes or more and 30 minutes or less.

The cooling temperature may be more than 0 ° C and not more than 4 ° C. When the solution of the mixture is cooled, the molten sulfur is recrystallized and a sulfur-carbon composite can be formed. If the temperature is higher than 4 ° C, recrystallization of sulfur may not occur. If the temperature is lower than 0 ° C, the solution of the mixture may freeze and recrystallization of sulfur may not occur easily, so that the sulfur-carbon composite may not be properly formed.

The weight of sulfur in the sulfur-carbon composite may be at least two times, more specifically at least five times, and specifically at most ten times the weight of carbon. If the weight of sulfur exceeds 10 times the weight of carbon, 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. When the weight of sulfur is less than twice the weight of carbon, carbon particles other than carbon existing on the surface of the sulfur particles are increased and the specific surface area is increased as the carbon content is increased, so that the amount of the binder added during the preparation of the cathode 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. It is more preferable for the electrode performance that the weight of sulfur is 5 times or more and 10 times or less than the weight of carbon.

The diameter of the sulfur-carbon composite particles may be specifically 0.5 micrometer or more, more specifically 1 micrometer or more, specifically 10 micrometer or less, more specifically 5 micrometer or less. In the present specification, the diameter of the sulfur-carbon composite particles means the largest diameter of the cross-sectional diameter of the sulfur-carbon composite particles.

The diameter of the carbon particles in the sulfur-carbon composite particle may be 1 nm or more and 100 nm or less.

The diameter of the sulfur particles in the sulfur-carbon composite particle may be 0.1 micrometer or more and 10 micrometer or less. 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. 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.

The method of manufacturing a sulfur-carbon composite according to one embodiment of the present application is characterized in that the solution is cooled while stirring to adjust the particle size of the sulfur-carbon composite (S30), and then the organic solvent is removed, Carbon composite powder (S40). The removal of the organic solvent in the mixture solution can be performed by washing and filtering the mixture solution, and the method is not limited.

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. Specifically, a conductive material such as stainless steel, aluminum, copper, or titanium can be used, and more specifically, a carbon-coated aluminum current collector can 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 be in 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 vary 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 cell, M, 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, dimethylacetamide, 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 >

1.5 g of sulfur and 0.15 g of carbon were dispersed using NMP (N-methyl-2-pyrrolidone) as an organic solvent, and this solution was heated to 150 캜 to stir sulfur while melting the sulfur, After forming, the sulfur-carbon composite prepared by cooling the solution to 1 캜 while stirring the solution at 1,000 rpm is shown in FIG. 3 and FIG. It was confirmed that particles having a diameter of 10 micrometers were uniformly formed.

≪ Example 2 >

The same procedure was followed as in Example 1 except that DMF (dimethylsulfoxide) was used as an organic solvent. The prepared sulfur-carbon composite is shown in Fig. It was confirmed that particles having a diameter of 10 micrometers were uniformly formed.

≪ Example 3 >

The same procedure was used as in Example 1 except that the stirring speed was adjusted to 3,000 rpm. The prepared sulfur-carbon composite is shown in FIGS. 6 and 7. FIG. It was confirmed that particles having a diameter of 2 micrometers to 5 micrometers were uniformly formed.

<Example 4>

The procedure of Example 1 was repeated except that 0.3 g of sulfur and 0.15 g of carbon were used. The prepared sulfur-carbon composite is shown in FIG.

&Lt; Comparative Example 1 &

FIG. 9 shows a case where a sulfur-carbon composite is produced by a ball mill method. It can be confirmed that the particle size is uneven.

&Lt; Comparative Example 2 &

The sulfur-carbon composite prepared by cooling at room temperature is shown in Fig. It can be confirmed that the particle size is large and uneven.

<Test Example>

A positive electrode mixture of 70 g of the positive electrode active material containing the sulfur-carbon composite prepared in Example 1 and Comparative Example 1, 20 g of carbon black as a conductive material, and 10 g of binder PVDF (polyphenyldinedifluoride) was dissolved in a solvent NMP (N-methyl- 2-pyrolidone) 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 charge / discharge characteristics of the coin cell were measured at 0.1 C using a charge / discharge measuring apparatus. The results are shown in FIGS. 11 and 12.

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.

100: sulfur-carbon composite particles
10: sulfur particles
20: Carbon particles

Claims (18)

Dispersing sulfur and carbon in an organic solvent to obtain a solution;
Heating the solution to melt and mix the sulfur to form a sulfur-carbon composite; And
And cooling the solution while stirring at a rate of 500 rpm to 10,000 rpm to adjust the particle diameter of the sulfur-carbon composite to be 0.5 micrometer or more and 10 micrometer or less. The method according to claim 1,
After adjusting the particle size of the sulfur-carbon composite,
Further comprising the step of removing the organic solvent and drying to obtain a sulfur-carbon composite powder. The method according to claim 1,
Wherein the cooling temperature is in the range of more than 0 ° C to 4 ° C. The method according to claim 1,
Wherein the step of controlling the particle size of the sulfur-carbon composite is performed by adding water to the mixture solution. The method of claim 4,
Wherein the weight ratio of water to organic solvent in the mixture solution is from 5: 1 to 1: 2. The method according to claim 1,
Wherein the heating temperature is not less than 120 ° C and not more than 180 ° C. The method according to claim 1,
Wherein the organic solvent is a polar organic solvent having a boiling point of 150 ° C or higher. The method according to claim 1,
The organic solvent is selected from the group consisting of dimethyl sulfoxide (150 ° C), isoamyl propionate (156 ° C), ethyl lactate (154 ° C), ethyl ethoxyacetate (156 ° C), 2-ethoxyethyl acetate (15O <0> C), ethyl-2-hydroxy-propionate (154 <0> C), and ethyl-3- methoxypropionate Methoxybutyl acetate (170 占 폚), 2-ethoxyethyl ether (185 占 폚), 2-butoxyethanol (171 占 폚), 3-ethoxy -Propanol (161 占 폚), diethylene glycol dodecyl ether (169 占 폚), dipropylene glycol methyl ether (188 占 폚), 2,6-dimethyl-4-heptanone ), 3-octanone (168 占 폚), 3-nonanone (188 占 폚), 5-nonanone (187 占 폚), 4-hydroxy- Methyl cyclohexanone (170 占 폚), 4-methylcyclohexanone (170 占 폚), 2,6-dimethylcyclohexanone (175 占 폚), 2,2,6-trimethyl Cyclohexanone (179 (179 ° C), hexyl acetate (169 ° C), amyl butyrate (185 ° C), isopropyl lactate (167 ° C), butyl lactate (186 ° C), ethyl 3-hydroxybutyrate 170 ° C), ethyl-3-ethoxypropionate (170 ° C), ethyl-3-hydroxybutyrate (180 ° C), propyl-2-hydroxypropionate (169 ° C), propylene glycol diacetate 186 占 폚), propylene glycol butyl ether at 170 占 폚, propylene glycol methyl ether propionate at 160 占 폚, diethylene glycol dimethyl ether at 162 占 폚, diethylene glycol dimethyl ether acetate at 165 占 폚, (178 ° C), diethylene glycol dimethyl ether (171 ° C), ethylene glycol butyl ether (171 ° C), diethylene glycol methyl ethyl ether (176 ° C), diethylene glycol methyl isopropyl ether Diethyl ether (189 占 폚), butyl butyrate (165 占 폚), ethyl-3-ethoxypropyl (193 ° C), and 2-butoxyethyl acetate (192 ° C), diethylene glycol monoethyl ether (202 ° C), diethylene glycol monomethyl ether ), Butyrolactone (204 DEG C), hexyl butyrate (205 DEG C), diethylene glycol methyl ether acetate (209 DEG C), diethylene glycol butyl methyl ether (212 DEG C) 212 ° C), tripropyl glycol dimethyl ether (215 ° C), triethylene glycol dimethyl ether (216 ° C), diethylene glycol ethyl ether acetate (217 ° C), diethylene glycol butyl ether acetate (245 ° C) Diethyleneglycol monobutyl ether (231 占 폚), tripropylglycol methyl ether (242 占 폚), diethylene glycol (245 占 폚), 1,2-propanediol (222 占 폚) (245 占 폚), catechol (245 占 폚), triethylene glycol methyl ether (249 占 폚), diethylene glycol Diethylene glycol monohexyl ether (260 占 폚), triethylene glycol butyl methyl ether (261 占 폚), triethylene glycol butyl ether (271 占 폚), and triethyleneglycol butyl ether (273 占 폚), and tetraethylene glycol dimethyl ether (276 占 폚). The method for producing a sulfur-carbon composite according to any one of claims 1 to 5, The method according to claim 1,
Wherein the weight of sulfur in the sulfur-carbon composite is 2 to 10 times the weight of carbon. delete delete A sulfur-carbon composite produced by the method of any one of claims 1 to 9. As the sulfur-carbon composite,
A sulfur particle containing at least one carbon particle therein; And
And carbon particles located on part or all of the surface of the sulfur particles,
The diameter of the sulfur-carbon composite particles is 0.5 micrometers or more and 10 micrometers or less,
Wherein the diameter of the carbon particles in the sulfur-carbon composite particle is 100 nm or less. 14. The method of claim 13,
Wherein the weight of sulfur in the sulfur-carbon composite is 2 to 10 times the weight of carbon. 14. The method of claim 13,
Wherein the diameter of the sulfur-carbon composite particles is greater than 1 micrometer but less than 5 micrometers. A positive electrode for a lithium-sulfur battery comprising the sulfur-carbon composite according to any one of claims 13 to 15. A cathode for a lithium-sulfur battery comprising the sulfur-carbon composite according to any one of claims 13 to 15; cathode; And a separator disposed between the anode and the cathode. A battery module comprising the lithium-sulfur battery of claim 17 as a unit cell.

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