KR102663583B1 - Manufacturing method of carbon -surfur complex - Google Patents

Abstract

The present invention relates to a method for producing a sulfur-carbon composite by controlling the particle size of the sulfur-carbon composite to a specific range.

Description

Manufacturing method of sulfur-carbon complex {MANUFACTURING METHOD OF CARBON -SURFUR COMPLEX}

The present invention relates to a method for producing a sulfur-carbon composite.

Recently, interest in energy storage technology has been increasing. As application areas expand to include mobile phones, camcorders, laptop PCs, and even electric vehicles, efforts to research and develop electrochemical devices are becoming more concrete.

Electrochemical devices are the field that is receiving the most attention in this regard, and among them, the development of secondary batteries capable of charging and discharging has become the focus of attention. Recently, in the development of such batteries, efforts have been made to improve capacity density and energy efficiency. Research and development is underway on the design of new electrodes and batteries.

Among the secondary batteries currently in use, the lithium secondary battery developed in the early 1990s has the advantage of having a higher operating voltage and much higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and lead sulfate batteries that use aqueous electrolyte solutions. is in the spotlight.

In particular, lithium-sulfur (Li-S) batteries are secondary batteries that use a sulfur-based material with an SS bond (Sulfur - Sulfur bond) as a positive electrode active material and lithium metal as a negative electrode active material. Sulfur, the main material of positive electrode active materials, has the advantage of being a very abundant resource, non-toxic, and having a low weight per atom. In addition, the theoretical discharge capacity of the lithium-sulfur battery is 1675 mAh/g-sulfur, and the theoretical energy density is 2,600 Wh/kg, which is similar to the theoretical energy density of other battery systems currently being studied (Ni-MH battery: 450 Wh/kg, Li- Since it is very high compared to (FeS battery: 480Wh/kg, Li-MnO ₂ battery: 1,000Wh/kg, Na-S battery: 800Wh/kg), it is the most promising battery among the batteries being developed to date.

During the discharge reaction of a lithium-sulfur battery, an oxidation reaction of lithium occurs at the cathode (anode), and a reduction reaction of sulfur occurs at the anode (cathode). Sulfur before discharge has a cyclic S ₈ structure. During a reduction reaction (discharge), the SS bond is broken and the oxidation number of S decreases, and during an oxidation reaction (charge), the SS bond is formed again and the oxidation number of S increases. Electrical energy is stored and generated using reduction reactions. During this reaction, sulfur is converted from cyclic S ₈ to linear lithium polysulfide (Li _{2 S} When reduced, lithium sulfide (Li ₂ S) is ultimately produced. Due to the reduction process of each lithium polysulfide, the discharge behavior of lithium-sulfur batteries is characterized by a gradual discharge voltage, unlike lithium-ion batteries.

These lithium-sulfur batteries exhibit higher energy densities than existing batteries, but in order to realize such high energy densities, the manufacture of high-capacity (high loading) electrodes is required, and the cell can be driven on high-capacity (high loading) electrodes. The skill to do this is very important.

Japanese published patent 2016-535716 “Carbon nanotube-sulfur composite including carbon nanotube aggregates and method for producing the same”

After conducting various studies, the present inventors confirmed that controlling the particle size of the sulfur-carbon composite has a significant impact on the operation of high loading electrodes, and that various methods for controlling the particle size of the composite can be applied. Thus, the present invention was completed.

Therefore, the purpose of the present invention is to adjust the particle size of the sulfur-carbon complex distributed within the electrode when manufacturing the cathode material for a battery to facilitate the entry and exit of the electrolyte solution within the electrode, thereby improving overvoltage during discharge and reducing initial reactivity. The aim is to provide a method for producing a sulfur-carbon composite with controlled particle size distribution so as to improve it.

In order to achieve the above object, the present invention

(a) mixing sulfur into a porous carbon material;

(b) heat treating the mixed porous carbon material and sulfur; a method for producing a sulfur-carbon composite comprising:

A method for producing a sulfur-carbon composite is provided in which the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to a range of 30 to 70 ㎛.

According to the present invention, by controlling the particle size of the sulfur-carbon complex, when manufacturing a battery, overvoltage can be improved and initial reactivity can be improved.

Figure 1 is a graph showing the particle size distribution of sulfur-carbon composites prepared in Examples 4-1 to 4-2 and Comparative Examples 4-1 to 4-3 of the present invention.
Figure 2 is a graph showing the initial discharge capacity of a battery made from the sulfur-carbon composite prepared in Examples 4-1 to 4-2 and Comparative Examples 4-1 to 4-3 of the present invention.

Hereinafter, the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to this specification.

In the drawings, parts unrelated to the description are omitted in order to clearly explain the present invention, and similar reference numerals are used for similar parts throughout the specification. Additionally, the sizes and relative sizes of components shown in the drawings are unrelated to actual scale and may be reduced or exaggerated for clarity of explanation.

Terms or words used in this specification and claims should not be construed as limited to their common or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

The term “composite” as used herein refers to a material that combines two or more materials to form physically and chemically different phases while exhibiting more effective functions.

A lithium secondary battery refers to a battery that can continuously store and use energy through oxidation-reduction reactions that occur at the anode and cathode. When charging and discharging occurs, lithium ions move along the electrolyte between the anode and cathode materials. It forms electrical neutrality with the electrons moving through this conductor and stores electrical or chemical energy.

Among these, lithium-sulfur batteries use sulfur as a positive electrode active material and lithium metal as a negative electrode active material. When a lithium-sulfur battery is discharged, an oxidation reaction of lithium occurs at the negative electrode, and a reduction reaction of sulfur occurs at the positive electrode. At this time, the reduced sulfur combines with lithium ions transferred from the cathode and is converted to lithium polysulfide, which ultimately involves a reaction to form lithium sulfide.

Lithium-sulfur batteries have a much higher theoretical energy density than existing lithium secondary batteries, and sulfur, which is used as a positive electrode active material, is an abundant resource and is inexpensive, so it is attracting attention as a next-generation battery due to the advantage of lowering the manufacturing cost of the battery. there is.

Despite these advantages, it is difficult to realize the full theoretical energy density in actual operation due to the low electrical conductivity and lithium ion conduction characteristics of sulfur, which is the positive electrode active material.

To improve the electrical conductivity of sulfur, methods such as complex formation with conductive materials such as carbon and polymers and coating are used. Among many methods, sulfur-carbon composite is the most widely used as a positive electrode active material because it is effective in improving the electrical conductivity of the positive electrode, but it is still insufficient in terms of charge/discharge capacity and efficiency. The capacity and efficiency of a lithium-sulfur battery can vary depending on the amount of lithium ions delivered to the anode. Therefore, facilitating the transfer of lithium ions into the sulfur-carbon composite is important for achieving high capacity and high efficiency of the battery.

In the development of such high loading electrodes, controlling the particle size of the sulfur-carbon composite has an important influence, and various methods for controlling the particle size of the composite can be applied.

Method for producing sulfur-carbon complex

Accordingly, in the present invention, in order to develop a high loading electrode with improved overvoltage and improved initial reactivity, a sulfur-carbon composite in which the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 30 to 70㎛ Provides a manufacturing method.

First, the method for producing a sulfur-carbon composite according to the present invention includes the steps of (a) mixing sulfur into a porous carbon material; and (b) heat treating the mixed porous carbon material and sulfur, wherein the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to a range of 30 to 70 ㎛.

The method for producing a sulfur-carbon composite according to the present invention includes the step of (a) mixing sulfur into a porous carbon material.

The porous carbon material provides a framework on which sulfur, a positive electrode active material, can be uniformly and stably immobilized and complements the electrical conductivity of sulfur to allow electrochemical reactions to proceed smoothly.

The porous carbon material can generally be manufactured by carbonizing precursors of various carbon materials. The porous carbon material contains irregular pores inside, and the porosity or porosity may be in the range of 10 to 90% of the total porosity. If the average diameter of the pores is less than the above range, the pore size is only at the molecular level, making sulfur impregnation impossible. Conversely, if it exceeds the above range, the mechanical strength of the porous carbon is weakened, making it desirable for application in the manufacturing process of electrodes. don't do it

The porous carbon material may be spherical, rod-shaped, needle-shaped, plate-shaped, tube-shaped, or bulk-shaped, and can be used without limitation as long as it is commonly used in lithium secondary batteries or lithium-sulfur batteries.

The porous carbon material may be any one that has a porous structure or has a high specific surface area and is commonly used in the art. For example, the porous carbon material includes graphite; graphene; Carbon black such as Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); Carbon fibers such as graphite nanofibers (GNF), carbon nanofibers (CNF), and activated carbon fibers (ACF); and activated carbon, but is not limited thereto.

In the present invention, before step (a), the porous carbon material is pulverized or agglomerated to adjust the particle size (based on D ₅₀ ) of the sulfur-carbon composite to a range of 30 to 70 ㎛ (1st stage adjustment). .

The grinding may be performed using an attrition mill, ball mill, jet mill, or resonance acoustic mixer. The grinding can be performed by adjusting conditions depending on the size or strength of the starting carbon.

Additionally, the agglomeration may use polymer carbonization or spray drying. The coagulation can be performed by adjusting the flow rate used in spray drying, concentration of the input solution, spraying temperature, spraying speed, etc.

By the above method, the particle size (based on D ₅₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 30 to 70㎛, preferably in the range of 40 to 60㎛.

In addition, by the above method, the particle size (based on D ₁₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 5 to 20㎛, preferably in the range of 5 to 15㎛, more preferably It can be adjusted in the range of 5 to 10㎛.

In addition, by the above method, the particle size (based on D ₉₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 100㎛ or less, preferably in the range of 80 to 100㎛.

Sulfur used in step (a) is inorganic sulfur (S ₈ ), Li ₂ S _n (n ≥ 1), organic sulfur compounds, and carbon-sulfur polymer [(C ₂ S _x ) _n , x=2.5 to 50, n ≥ 2] may be one or more types selected from the group consisting of. Preferably, inorganic sulfur (S ₈ ) can be used.

In addition, the sulfur is located not only inside the pores of the porous carbon material but also on the surface, and in this case, it will be present in less than 100%, preferably 1 to 95%, and more preferably 60 to 90% of the entire outer surface of the porous carbon material. You can. When the sulfur is within the above range on the surface of the porous carbon material, the maximum effect can be achieved in terms of electron transfer area and electrolyte wettability. Specifically, since sulfur is thinly and evenly impregnated on the surface of the porous carbon material in the above range region, the electron transfer contact area can be increased during the charge and discharge process. If the sulfur is located in 100% of the surface of the porous carbon material, the porous carbon material is completely covered with sulfur, which reduces the wettability of the electrolyte solution and reduces contact with the conductive material contained in the electrode, so it cannot receive electron transfer and participate in the reaction. It becomes impossible.

The sulfur-carbon complex can support a high content of sulfur due to pores of various sizes and three-dimensionally interconnected and regularly aligned pores within the structure. As a result, even if soluble polysulfide is generated through an electrochemical reaction, if it can be located inside the sulfur-carbon complex, the three-dimensional entangled structure is maintained even when the polysulfide is eluted, thereby suppressing the collapse of the anode structure. there is. As a result, the lithium secondary battery containing the sulfur-carbon composite has the advantage of being able to achieve high capacity even under high loading. Therefore, the sulfur loading of the sulfur-carbon composite according to the present invention may be 5 to 20 mg/cm ² .

In step (a), when mixing sulfur and the porous carbon material, the weight ratio of sulfur and the porous carbon material may be 9:1 to 7:3, preferably 8:2 to 7.5:2.5. If the weight ratio is less than the above range, as the content of the porous carbon material increases, the amount of binder added when producing the positive electrode slurry increases. This increase in the amount of binder added ultimately increases the sheet resistance of the electrode and acts as an insulator to prevent electrons from passing, which can reduce cell performance. In addition, since it is not possible to manufacture a composite with a high sulfur content due to the low sulfur content, there is a problem in that in order to manufacture an electrode with a high sulfur loading using a sulfur-carbon composite with a low sulfur content, the electrode becomes thick and the energy density increases accordingly. . Conversely, if the weight ratio exceeds the above range, the sulfur may clump together and have difficulty receiving electrons, making it difficult to directly participate in the electrode reaction.

In step (a), when mixing sulfur and the porous carbon material, the mixed weight of the sulfur and the porous carbon material may be 10 g or more. When mixing in small quantities of 10g or less, sulfur and porous carbon material can be easily mixed using a mortar, etc. However, when mixing in large quantities of 10g or more, mixing is not easy with a mortar, etc., so mixing must be done through a ball milling process. do.

In step (a), mixing may be performed when mixing sulfur and the porous carbon material. In the present invention, by mixing sulfur into a porous carbon material, the particle size (based on D ₅₀ ) of the sulfur-carbon composite can be adjusted to the range of 30 to 70㎛.

In the present invention, the method of mixing to achieve the desired particle size in step (a) is to first grind the carbon material to the desired particle size before mixing sulfur and carbon material, and then mix sulfur and carbon, or mix sulfur and carbon material. A high-speed rotating mixer can be used so that pulverization occurs simultaneously during the mixing process, or a ball mill can be used to control pulverization to occur along with mixing.

In the present invention, in order to adjust the particle size of the sulfur-carbon composite (based on D ₅₀ ) to the range of 30 to 70㎛, zirconia balls, carbon, and sulfur are placed in a container using a 2-roll mill equipment using the ball mill method. together and, for example, grinding and mixing can be performed by performing a ball mill at 200 rpm for 2-3 hours.

In addition, if the carbon obtained after grinding carbon with zirconia balls at 500 rpm using an attrition mill meets the desired particle size, take the carbon and mix carbon and sulfur together at 1500 rpm for 30 minutes using a Henschel mixer, for example. It can be done.

By the above method, the particle size (based on D ₅₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 30 to 70㎛, preferably in the range of 40 to 60㎛.

In addition, by the above method, the particle size (based on D ₁₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 5 to 20㎛, preferably in the range of 5 to 15㎛, more preferably It can be adjusted in the range of 5 to 10㎛.

In addition, by the above method, the particle size (based on D ₉₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 100㎛ or less, preferably in the range of 80 to 100㎛.

Thereafter, the method for producing a sulfur-carbon composite according to the present invention includes the step of (b) heat treating the mixed porous carbon material and sulfur.

The heat treatment can be performed at a temperature of 130°C to 170°C, and the heat treatment time is not particularly limited, but can be performed from 15 minutes to 2 hours. If the temperature range exceeds 170°C, there is a problem that sulfur vaporizes, and if the temperature range is below 130°C, there is a problem that sulfur does not dissolve and is not evenly distributed. In addition, if the heat treatment time is less than 15 minutes, there is a problem that it is not sufficiently melted and impregnated, and if it exceeds 2 hours, there is a problem that some of the sulfur is vaporized or unevenly impregnated.

In the present invention, in order to adjust the particle size (based on D ₅₀ ) of the sulfur-carbon composite to a range of 30 to 70㎛, the sulfur-carbon composite may be pulverized after step (b).

Specifically, the grinding can be used without particular restrictions as long as it is a grinding method that does not dissolve sulfur, and preferably a ball mill, attrition mill, or jet mill can be used.

The grinding may be performed, for example, by using a ball mill method using roll-mill equipment, placing the zirconia ball and the composite together and grinding at 200 rpm for 2 hours.

By the above method, the particle size (based on D ₅₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 30 to 70㎛, preferably in the range of 40 to 60㎛.

In addition, by the above method, the particle size (based on D ₁₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 5 to 20㎛, preferably in the range of 5 to 15㎛, more preferably It can be adjusted in the range of 5 to 10㎛.

In addition, by the above method, the particle size (based on D ₉₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 100㎛ or less, preferably in the range of 80 to 100㎛.

In the present invention, in order to adjust the particle size (based on D ₅₀ ) of the sulfur-carbon composite to a range of 30 to 70㎛, after step (b), (c) a binder, a dispersant, and a conductive agent are added to the sulfur-carbon composite. A step of preparing a slurry mixed with ash may be additionally performed.

Step (c) may be performed in a batch vessel. The batch vessel can be equipped with all equipment for mixing using balls. For example, an impeller may be provided inside.

In addition, in the case of conventional slurry production, when using a large container of 200 ml or more, the physical properties of the slurry deteriorated, so it was manufactured using a small container of 200 ml or less. However, the slurry production method of the present invention uses the slurry production conditions (milling ball) By optimizing the amount and mixing rpm, it became possible to use larger containers of 200ml or more and mix more than 100g of slurry.

In this way, the batch container can be a large container of 200ml or more, and the upper limit of capacity is not particularly limited, but preferably 1000ml or less. There is no particular limitation on the amount of slurry that can be produced, but preferably, the slurry can be produced in an amount of 1000 g or less.

During the mixing, milling balls may be used for dispersion, or blades may be used to grind the mixture.

In the method for producing a sulfur-carbon composite according to the present invention, mixing is performed using a rotational stirring method, and it is preferable to stir at a higher set rpm. The specific rpm value may vary depending on the mixing scale. Preferably, when mixing the slurry, mixing can be divided into three stages.

Among the three mixing steps, step 1 is a step of mixing the binder and dispersant and preparing it into a uniform solution, and step 2 is a step of dispersing the conductive material in the mixed solution prepared in step 1, Step 3 is a step for dispersing the complex in the mixed solution prepared in step 2 above. In each mixing step, mixing can be performed at 500 to 1000 rpm in the first step, 2000 to 5000 rpm in the second step, and 2000 to 5500 rpm in the third step.

The milling balls used in the method for producing a sulfur-carbon composite according to the present invention may be zirconia (ZrO ₂ ) balls or alumina (Al ₂ O ₃ ) balls.

By the above method, the particle size (based on D ₅₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 30 to 70㎛, preferably in the range of 40 to 60㎛.

In addition, by the above method, the particle size (based on D ₁₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 5 to 20㎛, preferably in the range of 10 to 20㎛, more preferably It can be adjusted in the range of 15 to 20㎛.

In addition, by the above method, the particle size (based on D ₉₀ ) of the sulfur-carbon composite of the present invention can be adjusted to the range of 80 to 120㎛, preferably in the range of 90 to 120㎛, more preferably It can be adjusted in the range of 100 to 120㎛.

sulfur-carbon complex

In the sulfur-carbon composite of the present invention, the particle size of the sulfur-carbon composite is adjusted to a range of 30 to 70 ㎛ (based on D ₅₀ ) by controlling the particle size of the sulfur-carbon under various conditions at various stages during production. do.

The sulfur-carbon composite of the present invention includes a porous carbon material; And sulfur is included in at least a portion of the interior and surface of the porous carbon material.

The porous carbon material provides a framework on which sulfur, a positive electrode active material, can be uniformly and stably immobilized and complements the electrical conductivity of sulfur to allow electrochemical reactions to proceed smoothly.

The porous carbon material can generally be manufactured by carbonizing precursors of various carbon materials. The porous carbon material contains irregular pores inside, and the average diameter of the pores is in the range of 1 to 200 nm, and the porosity or porosity may be in the range of 10 to 90% of the total porosity volume. If the average diameter of the pores is less than the above range, the pore size is only at the molecular level, making sulfur impregnation impossible. Conversely, if it exceeds the above range, the mechanical strength of the porous carbon is weakened, making it desirable for application in the manufacturing process of electrodes. don't do it

The porous carbon material may be spherical, rod-shaped, needle-shaped, plate-shaped, tube-shaped, or bulk-shaped, and can be used without limitation as long as it is commonly used in lithium secondary batteries, lithium-sulfur batteries, etc.

The porous carbon material may be any one that has a porous structure or has a high specific surface area and is commonly used in the art. For example, the porous carbon material includes graphite; graphene; Carbon black such as Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); Carbon fibers such as graphite nanofibers (GNF), carbon nanofibers (CNF), and activated carbon fibers (ACF); and activated carbon, but is not limited thereto.

The sulfur is selected from the group consisting of inorganic sulfur (S ₈ ), Li ₂ S _n (n ≥ 1), organic sulfur compounds and carbon-sulfur polymers [(C ₂ S _x ) _n , x=2.5 to 50, n ≥ 2]. There may be one or more selected types. Preferably, inorganic sulfur (S ₈ ) can be used.

In the sulfur-carbon composite according to the present invention, the weight ratio of the above-described sulfur to the porous carbon material may be 9:1 to 7:3, preferably 8:2 to 7.5:2.5. If the weight ratio is less than the above range, as the content of the porous carbon material increases, the amount of binder added when producing the positive electrode slurry increases. This increase in the amount of binder added ultimately increases the sheet resistance of the electrode and acts as an insulator to prevent electrons from passing, which can reduce cell performance. Conversely, if the weight ratio exceeds the above range, the sulfur may clump together and have difficulty receiving electrons, making it difficult to directly participate in the electrode reaction.

In addition, the sulfur is located not only inside the pores of the porous carbon material but also on the surface, and in this case, it will be present in less than 100%, preferably 1 to 95%, and more preferably 60 to 90% of the entire outer surface of the porous carbon material. You can. When the sulfur is within the above range on the surface of the porous carbon material, the maximum effect can be achieved in terms of electron transfer area and electrolyte wettability. Specifically, since sulfur is thinly and evenly impregnated on the surface of the porous carbon material in the above range region, the electron transfer contact area can be increased during the charge and discharge process. If the sulfur is located in 100% of the surface of the porous carbon material, the porous carbon material is completely covered with sulfur, which reduces the wettability of the electrolyte solution and reduces contact with the conductive material contained in the electrode, so it cannot receive electron transfer and participate in the reaction. It becomes impossible.

As mentioned earlier, the sulfur-carbon composite of the present invention has a particle size (based on D ₅₀ ) of 30 to 70 as the particle size of the sulfur-carbon composite is adjusted under various conditions at various stages during production. It can be in the range of ㎛. More specifically, the particle size (based on D ₅₀ ) of the sulfur-carbon composite may range from 40 to 60 ㎛, 45 to 60 ㎛, or 50 to 60 ㎛. When the composite particle size is within the above range, the size of the pores formed in the electrode structure can be larger than the size of the pores formed by the composite with a smaller particle size, making it easier to enter and exit the electrolyte solution.

In addition, in the sulfur-carbon composite of the present invention, the particle size (based on D ₁₀ ) of the sulfur-carbon composite can be adjusted to be in the range of 20㎛ or less, specifically in the range of 5 to 20㎛, preferably It may be in the range of 5 to 15㎛, more preferably in the range of 5 to 10㎛. If the fine powder increases, the amount of binder for forming the electrode may increase, causing resistance, and if the fine powder becomes too small, the structure of the electrode may not be dense, which may have a negative effect on electrode conductivity.

Additionally, in the sulfur-carbon composite of the present invention, the particle size (based on D ₉₀ ) of the sulfur-carbon composite can be in the range of 100 μm or less. More specifically, the particle size (based on D ₉₀ ) of the sulfur-carbon composite may range from 80 to 100 ㎛. If it is larger than the above range, the problem of the composite breaking inside the electrode will occur when the thickness is reduced by rolling the electrode later. In addition, even without rolling, the presence of a composite with a large particle size can reduce the non-uniformity of the electrode, affecting electrode performance.

The sulfur-carbon complex can support a high content of sulfur due to pores of various sizes and three-dimensionally interconnected and regularly aligned pores within the structure. As a result, even if soluble polysulfide is generated through an electrochemical reaction, if it can be located inside the sulfur-carbon complex, the three-dimensional entangled structure is maintained even when the polysulfide is eluted, thereby suppressing the collapse of the anode structure. there is. As a result, the lithium secondary battery containing the sulfur-carbon composite has the advantage of being able to achieve high capacity even under high loading. Therefore, the sulfur loading of the sulfur-carbon composite according to the present invention may be 5 to 20 mg/cm ² .

Anode for lithium secondary battery

The sulfur-carbon composite presented in the present invention can be preferably used as a positive electrode active material for lithium secondary batteries.

The positive electrode is manufactured by applying and drying a composition for forming a positive electrode active material layer on a positive electrode current collector. The composition for forming the positive electrode active material layer is prepared by mixing the above-described sulfur-carbon composite with a conductive material and a binder, then applying it to a current collector and drying it at 40 to 70 ° C. for 4 to 12 hours.

Specifically, in order to provide additional conductivity to the prepared sulfur-carbon composite, a conductive material may be added to the positive electrode composition. The conductive material serves to allow electrons to move smoothly within the anode. There is no particular limitation as long as it has excellent conductivity and can provide a large surface area without causing chemical changes in the battery, but is preferably carbon-based. Use substances.

The carbon-based materials include natural graphite, artificial graphite, expanded graphite, graphite such as graphene, activated carbon, channel black, furnace black, and thermal. Carbon black, such as thermal black, contact black, lamp black, and acetylene black; One type selected from the group consisting of carbon nanostructures such as carbon fiber, carbon nanotube (CNT), fullerene, and combinations thereof can be used.

In addition to the carbon-based materials, depending on the purpose, metallic fibers such as metal mesh; Metallic powders such as copper (Cu), silver (Ag), nickel (Ni), and aluminum (Al); Alternatively, organic conductive materials such as polyphenylene derivatives can also be used. The above conductive materials can be used alone or in combination.

Additionally, in order to provide adhesion to the positive electrode active material to the current collector, the positive electrode composition may additionally include a binder. The binder must be well soluble in a solvent, must form a well-conductive network between the positive electrode active material and the conductive material, and must also have adequate impregnability of the electrolyte solution.

The binder applicable to the present invention may be any binder known in the art, and specifically, a fluororesin binder containing polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE). ; Rubber-based binders including styrene-butadiene rubber, acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; polyalcohol-based binder; Polyolefin-based binders including polyethylene and polypropylene; It may be one type, a mixture of two or more types, or a copolymer selected from the group consisting of polyimide-based binder, polyester-based binder, and silane-based binder, but is of course not limited thereto.

The content of the binder resin may be 0.5 to 30% by weight based on the total weight of the pole, but is not limited thereto. If the content of the binder resin is less than 0.5% by weight, the physical properties of the positive electrode may deteriorate and the positive electrode active material and the conductive material may fall off, and if it exceeds 30% by weight, the ratio of the active material and the conductive material in the positive electrode is relatively reduced. Battery capacity may be reduced.

The solvent for preparing the positive electrode composition in a slurry state must be easy to dry and can dissolve the binder well, but most preferably, it can maintain the positive electrode active material and conductive material in a dispersed state without dissolving them. When the solvent dissolves the positive electrode active material, the specific gravity of sulfur in the slurry (D = 2.07) is high, so the sulfur settles in the slurry, causing problems in the conductive network due to sulfur concentrating on the current collector during coating, which tends to cause problems in battery operation. there is.

The solvent according to the present invention can be water or an organic solvent, and the organic solvent includes one or more selected from the group of dimethylformamide, isopropyl alcohol, acetonitrile, methanol, ethanol, and tetrahydrofuran. possible.

The positive electrode composition can be mixed in a conventional manner using a conventional mixer, such as a rate mixer, high-speed shear mixer, or homomixer.

The positive electrode composition can be applied to a current collector and dried in vacuum to form a positive electrode. The slurry can be coated on the current collector at an appropriate thickness depending on the viscosity of the slurry and the thickness of the positive electrode to be formed, and can preferably be appropriately selected within the range of 10 to 300 ㎛.

At this time, there is no limitation to the method of coating the slurry, for example, doctor blade coating, dip coating, gravure coating, slit die coating, spin coating ( It can be manufactured by performing spin coating, comma coating, bar coating, reverse roll coating, screen coating, cap coating, etc.

The positive electrode current collector can generally be made to have a thickness of 3 to 500 ㎛, and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, conductive metals such as stainless steel, aluminum, copper, and titanium can be used, and preferably an aluminum current collector can be used. These positive electrode current collectors can take various forms such as films, sheets, foils, nets, porous materials, foams, or non-woven fabrics.

lithium secondary battery

As an embodiment of the present invention, a lithium secondary battery includes the above-described positive electrode; A negative electrode containing lithium metal or lithium alloy as a negative electrode active material; A separator interposed between the anode and the cathode; and an electrolyte that is impregnated in the cathode, anode, and separator and includes a lithium salt and an organic solvent.

In particular, the lithium secondary battery of the present invention may be a lithium-sulfur battery containing sulfur in the positive electrode.

The negative electrode is a negative electrode active material that can reversibly intercalate or deintercalate lithium ions (Li ⁺ ), and a material that can react with lithium ions to reversibly form a lithium-containing compound. , lithium metal or lithium alloy can be used. The material capable of reversibly intercalating or deintercalating lithium ions may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material that can react with the lithium ion to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. For example, the lithium alloy may be 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.

Additionally, in the case of lithium-sulfur batteries, during charging and discharging, sulfur used as a positive electrode active material may be converted into an inert material and adhere to the surface of the lithium negative electrode. As such, inactive sulfur refers to sulfur in a state in which sulfur can no longer participate in the electrochemical reaction of the anode after undergoing various electrochemical or chemical reactions, and the inactive sulfur formed on the surface of the lithium cathode acts as a protective film of the lithium cathode. It also has the advantage of acting as a layer. Therefore, lithium metal and inert sulfur formed on the lithium metal, such as lithium sulfide, may be used as a negative electrode.

In addition to the negative electrode active material, the negative electrode of the present invention may further include a pretreatment layer made of a lithium ion conductive material and a lithium metal protective layer formed on the pretreatment layer.

The separator interposed between the anode and the cathode separates or insulates the anode and the cathode from each other and enables the transport of lithium ions between the anode and the cathode, and may be made of a porous non-conductive or insulating material. This separator is an insulator with high ion permeability and mechanical strength and may be an independent member such as a thin film or film, or may be a coating layer added to the anode and/or cathode. Additionally, when a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The pore diameter of the separator is generally 0.01 to 10 ㎛, and the thickness is generally preferably 5 to 300 ㎛. Glass electrolyte, polymer electrolyte, or ceramic electrolyte may be used as the separator. For example, sheets, non-woven fabrics, kraft paper, etc. made of olefinic polymers such as chemical-resistant and hydrophobic polypropylene, glass fiber, or polyethylene are used. Representative examples currently on the market include the Celgard series (Celgard ^R 2400, 2300 from Hoechest Celanese Corp.), polypropylene separator (from Ube Industries Ltd. or Pall RAI), and polyethylene series (Tonen or Entek).

The solid electrolyte separator may contain less than about 20% by weight of a non-aqueous organic solvent, and in this case, it may further contain an appropriate gel-forming compound (gelling agent) to reduce the fluidity of the organic solvent. Representative examples of such gel-forming compounds include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile.

The electrolyte impregnated in the cathode, anode, and separator is a non-aqueous electrolyte containing lithium salt and is composed of lithium salt and an electrolyte solution. Non-aqueous organic solvent, organic solid electrolyte, and inorganic solid electrolyte are used as the electrolyte solution.

The lithium salt of the present invention is a material that is easily soluble in non-aqueous organic solvents, such as LiSCN, LiCl, LiBr, LiI, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiClO ₄ , LiAlCl ₄ , Li(Ph) ₄ , LiC(CF ₃ SO ₂ ) ₃ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(SFO ₂ ) ₂ , LiN(CF ₃ CF ₂ SO ₂ ) ₂ , lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenyl borate, lithium imide, and a group consisting of combinations thereof. One or more may be included from.

The concentration of the lithium salt may range from 0.2 to 2 M, depending on several factors such as the exact composition of the electrolyte mixture, solubility of the salt, conductivity of the dissolved salt, charging and discharging conditions of the cell, operating temperature and other factors known in the lithium battery field. Specifically, it may be 0.6 to 2 M, more specifically 0.7 to 1.7 M. If less than 0.2 M is used, the conductivity of the electrolyte may decrease and electrolyte performance may deteriorate, and if more than 2 M is used, the viscosity of the electrolyte may increase and the mobility of lithium ions (Li ⁺ ) may be reduced.

The non-aqueous organic solvent must dissolve the lithium salt well, and non-aqueous organic solvents of the present invention include, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, Ethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trime Aprotic substances such as toxin methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, ethyl propionate, etc. An organic solvent may be used, and the organic solvent may be one or a mixture of two or more organic solvents.

The organic solid electrolyte includes, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, poly vinylidene fluoride, ionic dissociation. A polymer containing a group, etc. may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ Nitride, halide, sulfate, etc. of Li such as SiO ₄ -LiI-LiOH, Li ₃ PO4-Li ₂ S-SiS ₂ may be used.

The electrolyte of the present invention includes, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, and nitroamine for the purpose of improving charge/discharge characteristics, flame retardancy, etc. Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. . In some cases, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further included to provide incombustibility, and carbon dioxide gas may be further included to improve high-temperature preservation characteristics, and FEC (Fluoro-ethylene carbonate), PRS (Propene sultone), FPC (Fluoro-propylene carbonate), etc. may be further included.

The electrolyte can be used as a liquid electrolyte or in the form of a solid electrolyte separator. When used as a liquid electrolyte, it further includes a physical separator that has the function of physically separating electrodes and is made of porous glass, plastic, ceramic, or polymer.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is clear to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the attached patent claims.

[Example]

Preparation of sulfur-carbon complexes

[Example 1] (Particle size control of carbon first)

200 g of carbon nanotubes (manufactured by LG Chemical) with a specific surface area of 200 cm ² were ground at 500 rpm for 5 minutes using a 5 mm sized zirconia ball using an attrition mill (M tech, attrition mill 5L).

50 g of the pulverized carbon nanotubes were mixed with 150 g of sulfur (Aldrich's α-Sulfur) using a blade mixing process (using a Henschel mixer) at 1500 rpm for 30 minutes. There was almost no effect of pulverizing carbon in the mixing process. Afterwards, a sulfur-carbon composite was prepared by heat treatment in an oven at 155°C for 30 minutes.

[Example 2] (Particle size control when mixing sulfur and carbon)

50 g of the same carbon nanotubes as in Example 1 were mixed with 150 g of sulfur (α-Sulfur from Aldrich) through a ball milling process. The ball milling process was performed for 2 hours under milling conditions of 200 RPM using 5 mm sized zirconia balls.

Afterwards, a sulfur-carbon composite was prepared by heat treatment in an oven at 155°C for 30 minutes.

[Example 3] (Particle size control after composite production)

50 g of the same carbon nanotubes as in Example 1 were mixed with 150 g of sulfur (α-Sulfur from Aldrich) through a blade mixing (using a Henschel mixer) process. There was almost no effect of pulverizing carbon in the mixing process. Afterwards, a sulfur-carbon composite was prepared by heat treatment in an oven at 155°C for 30 minutes. Thereafter, the prepared sulfur-carbon composite was subjected to another ball milling process using 5 mm sized zirconia balls under milling conditions of 200 RPM for 2 hours.

[Example 4-1] (Particle size control in slurry production step)

50 g of the same carbon nanotubes as in Example 1 were mixed with 150 g of sulfur (α-Sulfur from Aldrich) through a blade mixing (using a Henschel mixer) process. In the above mixing process, there was almost no effect of pulverizing carbon. Afterwards, a sulfur-carbon composite was prepared by heat treatment in an oven at 155°C for 30 minutes.

The sulfur-carbon composite: binder: dispersant: conductive material was mixed in a weight ratio of 87:7:1:5 in a stainless steel slurry container with a volume of 500 ml to prepare 240 g of slurry (solid content: 25%). A polyacrylic binder was used as the binder, a polyvinyl-based dispersant was used as the dispersant, and vapor grown carbon fibers (VGCF) was used as the conductive material.

ZrO ₂ balls were added to the slurry so that the weight ratio of slurry:ZrO ₂ balls was 2:1 in the container, and then stirred for 30 minutes using an impeller with a diameter of 5 cm. During stirring, the mixing rpm was set at 800 rpm in step 1, 4000 rpm in step 2, and 5000 rpm in step 3, and the mixture was stirred for the same time in each step to prepare a slurry for producing a positive electrode.

[Example 4-2]

A slurry (25% solid content) was prepared in the same manner as Example 4-1, except that the stirring time was increased from 30 minutes to 60 minutes.

[Comparative Example 1]

The composite was pulverized in the same manner as in Example 3, except that the D50 was further pulverized to 10 μm.

[Comparative Example 2]

The carbon material was pulverized in the same manner as in Example 1, large particles were removed through classification, and a sulfur-carbon composite was prepared in the same manner as in Example 1, except that D ₅₀ was 25㎛.

[Comparative Example 3]

The carbon material was pulverized in the same manner as in Example 1, large particles were removed through classification, and a sulfur-carbon composite was prepared in the same manner as in Example 2, except that D ₅₀ was 73㎛.

[Comparative Example 4-1]

A slurry (25% solid content) was prepared in the same manner as in Example 4-1, except that the stirring time was increased while checking the particle size of the slurry until the particle size reached a point where it was reduced to 31㎛.

[Comparative Example 4-2]

A slurry (25% solid content) was prepared in the same manner as in Example 4-1, except that the stirring time was increased while checking the particle size of the slurry and stirring was performed until the particle size reached a point where the particle size decreased to 22㎛.

[Comparative Example 4-3]

A slurry (25% solid content) was prepared in the same manner as in Example 4-1, except that the stirring time was increased while checking the particle size of the slurry and stirring was performed until the particle size (D ₅₀ ) reached 65㎛.

Experiment example 1: Slurry physical property evaluation

(Particle size distribution measurement)

The particle size distribution of the sulfur-carbon composites prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was measured using a bluewave product from Microtrac, and is shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative example 2 Comparative Example 3 D ₁₀ (㎛) 12.0 17.2 18.0 4.55 8.91 48.22 D ₅₀ (㎛) 37.25 56.4 51.0 10.05 25.52 72.78 D ₉₀ (㎛) 81.22 103.0 92.0 16.94 65.52 112.7

Through the results in Table 1, it was found that when manufacturing the sulfur-carbon composite, there was a difference in the particle size distribution of the sulfur-carbon composite depending on the particle size control conditions.

In addition, the particle size distribution of the slurries prepared in Examples 4-1 to 4-2 and Comparative Examples 4-1 to 4-3 was measured using a bluewave product from Microtrac, and is shown in Table 2 and Figure 1 below.

Example 4-1 Example 4-2 Comparative Example 4-1 Comparative Example 4-2 Comparative Example 4-3 D ₅₀ (㎛) 49.42 40.63 31.08 21.76 65.27

In addition, through the results in Table 2, it was found that there was a difference in the particle size distribution of the sulfur-carbon composite depending on the milling time in the slurry production step containing the sulfur-carbon composite.

Experiment example 2: Battery performance evaluation

Using the sulfur-carbon composites prepared in Examples 1 to 3 and Comparative Examples 1 to 4, a slurry was prepared with a weight ratio of sulfur-carbon composite: conductive material: binder = 90:5:5, and then 20 ㎛ thick aluminum. An electrode was manufactured by coating a current collector of foil. At this time, carbon black was used as the conductive material, and styrene butadiene rubber and carboxymethyl cellulose were used as the binder. Afterwards, electrodes were manufactured by drying overnight in an oven at 50°C.

Additionally, the slurry prepared in Examples 4-1 to 4-2 and Comparative Examples 5-1 to 5-3 was coated on a current collector in the same manner to prepare an electrode.

A coin cell was manufactured using the prepared positive electrode as an anode, polyethylene as a separator, and lithium foil with a thickness of 45 ㎛ as a negative electrode. At this time, the coin cell used an electrolyte prepared by dissolving 1 M LiTFSI and 3 wt% LiNO ₃ in an organic solvent consisting of DOL/DME solvent (1:1 volume ratio).

(Charging and discharging characteristics evaluation)

For the coin cell manufactured above, changes in charge/discharge characteristics were tested using a charge/discharge measuring device. Using the obtained battery, the initial discharge/charge was performed at 0.1C/0.1C for the initial 2.5 cycles, then 3 cycles at 0.2C/0.2C, and then at 0.5C/0.3C.

The above results were measured and shown in Table 3 and Figure 2 below. In Table 3 and Figure 2 below, porosity was calculated using the actual density and weight by measuring the electrode thickness, and loading was calculated using the weight and area of the electrode.

Specific capacity
(mAh/g) Porosity
(%) Loading
(mAh/ ^cm2 ) Example 1 976 68 5.1 Example 2 1044 68 5.9 Example 3 1016 68 5.8 Comparative Example 1 300 60 5.3 Comparative Example 2 962 68 5.4 Comparative Example 3 957 67 5.0

Through Table 3 above, it was found that the particle size of the composite affects the performance of the cell.

In addition, a graph showing the initial charge and discharge characteristics of the batteries manufactured in Examples 4-1 to 4-2 and Comparative Examples 4-1 to 4-3 is shown in Figure 2, and through Figure 2, the slurry according to the present invention can be seen. It was found that cell performance improved as particle size was limited.

Claims (19)

(a) mixing sulfur into a porous carbon material; and
(b) heat treating the mixed porous carbon material and sulfur; a method for producing a sulfur-carbon composite comprising:
A method of producing a sulfur-carbon composite wherein the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to a range of 37.25 to 70㎛. According to paragraph 1,
Before step (a), the porous carbon material is pulverized or agglomerated, and the particle size of the sulfur-carbon composite (based on D ₅₀ ) is adjusted to a range of 37.25 to 70 ㎛. Manufacture of a sulfur-carbon composite. method. According to paragraph 2,
The method of producing a sulfur-carbon composite is characterized in that the grinding is performed using an attrition mill, ball mill, jet mill, or resonance acoustic mixer. . According to paragraph 2,
A method for producing a sulfur-carbon composite, characterized in that the agglomeration uses polymer carbonization or spray drying. According to paragraph 1,
In step (a), when mixing sulfur into the porous carbon material, the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 37.25 to 70 ㎛ by mixing. Method for producing sulfur-carbon complex. According to clause 5,
The ball milling is characterized in that the carbon material is first pulverized to a desired particle size before the mixing process of sulfur and carbon material, and then the sulfur and carbon are mixed, or mixing occurs so that pulverization occurs together during the mixing process of sulfur and carbon material, Method for producing sulfur-carbon complex. According to paragraph 1,
After step (b), the sulfur-carbon composite is pulverized, and the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 37.25 to 70㎛. In clause 7,
A method for producing a sulfur-carbon composite, wherein the grinding is performed using a ball mill, attrition mill, or jet mill. According to paragraph 1,
After step (b), (c) preparing a slurry by mixing the sulfur-carbon composite with a binder, a dispersant, and a conductive material; is further performed to determine the particle size (based on D ₅₀ ) of the sulfur-carbon composite. A method for producing a sulfur-carbon composite, characterized in that it is adjusted in the range of 37.25 to 70㎛. According to clause 9,
The method of producing a sulfur-carbon composite, characterized in that step (c) is performed in a batch vessel equipped with an impeller therein. According to clause 9,
The step (c) is a method of producing a sulfur-carbon composite, characterized in that grinding using a milling ball or a blade. According to any one of claims 5 to 9,
A method of producing a sulfur-carbon composite, wherein the milling balls are zirconia (ZrO ₂ ) balls or alumina (Al ₂ O ₃ ) balls. According to clause 9,
When mixing the slurry, the first step is to mix the binder and the dispersant, the second step is to disperse the conductive material in the mixed solution prepared in step 1, and the third step is to disperse the sulfur-carbon complex in the mixed solution prepared in step 2. A method for producing a sulfur-carbon composite, characterized in that mixing. According to clause 13,
When mixing the slurry,
The first stage is 500 to 1000 rpm,
The second stage is 2000 to 5000 rpm,
The third step is a method of producing a sulfur-carbon composite, characterized in that mixing is performed at 2000 to 5500 rpm. According to paragraph 1,
A method for producing a sulfur-carbon composite, wherein the sulfur and the porous carbon material are mixed at a weight ratio of 9:1 to 7:3. According to paragraph 2,
A method for producing a sulfur-carbon composite, characterized in that the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 40 to 60㎛. According to clause 5,
A method for producing a sulfur-carbon composite, characterized in that the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 45 to 60㎛. In clause 7,
A method for producing a sulfur-carbon composite, characterized in that the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 45 to 60㎛. According to clause 9,
A method for producing a sulfur-carbon composite, characterized in that the particle size (based on D ₅₀ ) of the sulfur-carbon composite is adjusted to the range of 40 to 50㎛.