Block copolymer, crosslinked block copolymer containing the block copolymer, sulfur-carbon composite, and method for producing sulfur-carbon composite

Abstract

A sulfur-carbon composite according to one embodiment of the present invention comprises a crosslinked block copolymer, which is manufactured from a block copolymer having a first block including a first repeat unit having a terminal pyrene group and a second block including a second repeat unit having a cationic functional group. By coating the sulfur-carbon composite with the crosslinked block copolymer, lithium polysulfides leached from the positive electrode of a lithium-sulfur battery are prevented from being transferred to the negative electrode. Therefore, the accumulation of sulfur particles on the surface of the lithium metal in the negative electrode is prevented, thereby maintaining the charge / discharge capacity of the lithium-sulfur battery and improving its lifespan.

Description

[Technical Field]

[0001] The present invention relates to a block copolymer capable of capturing polysulfides eluted from a positive electrode to improve the life of the battery, and a secondary battery containing the block copolymer.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0110368, filed on August 31, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0003] As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing. Among secondary batteries, lithium secondary batteries have become common and are widely used due to their high energy density, working potential, long cycle life, and low self-discharge rate.

[0004] In addition, in recent years, with growing interest in environmental issues, active research has been conducted on electric vehicles (EVs) and hybrid electric vehicles (HEVs) that can replace vehicles that use fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. Lithium secondary batteries, which have high energy density, high discharge voltage, and output stability, have been mainly researched and used as power sources for such electric vehicles and hybrid electric vehicles.

[0005] A lithium secondary battery has a structure in which a porous separator is interposed between an electrode assembly including a positive electrode and a negative electrode, each of which has an active material coated on a current collector, and a non-aqueous electrolyte containing a lithium salt is impregnated in the electrode assembly.

[0006] Currently, the lithium secondary battery market is dominated by technology based on the pairing of a lithium cobalt oxide (LiCoO2) cathode and a graphite anode. While most other types of batteries (Ni-CD, Ni-MH, etc.) have a rated voltage of 1.5V, lithium secondary batteries have a rated voltage of approximately 3.6V. Their volumetric and mass energy densities are approximately 300-500Wh / l and 160-200Wh / kg, respectively, which are among the highest levels of any commercially available battery. Lithium secondary batteries also have low self-discharge and long lifespans (500 or 1,000 cycles). Despite these impressive performances, all lithium-ion batteries have reached a plateau in performance, with limited prospects for improvement.

[0007] Therefore, lithium-sulfur (Li-S) batteries are gaining attention as an alternative to lithium-ion batteries.

[0008] Like conventional lithium-ion secondary batteries, lithium-sulfur batteries operate by lithium ions moving within an electrolyte between a positive electrode and a negative electrode. However, because lithium-sulfur batteries use only simple sulfur, they operate based on a redox reaction between sulfur and lithium ions, unlike conventional lithium-ion secondary batteries, in which lithium ions enter the gaps between the molecules of the electrode active material, transforming the electrode structure to store energy. Therefore, lithium-sulfur batteries are not limited in electrode structure compared to conventional lithium-ion secondary batteries, and theoretically can have a larger capacity for the same volume. Due to these characteristics, in a lithium-sulfur battery consisting of a sulfur cathode and a lithium metal anode, assuming that the ring-structured monomeric sulfur (S8) reacts completely to form lithium polysulfide (Li2S), the theoretical capacity is 1,675mAh / g and the theoretical energy density is 2,600Wh / kg, which is three to six times higher than other conventional battery systems (Ni / MH battery: 450Wh / kg, Li / FeS: 480Wh / kg, Li / MnO2: 1,000Wh / kg, Na / S: 800Wh / kg).

[0009] On the other hand, conventional transition metal oxide-based lithium-ion secondary batteries are considered to contain heavy metal pollutants because their cathodes use oxides of nickel (Ni), cobalt (Co), and manganese (Mn), which have densities higher than those of heavy metals (metals of 5 g / mL or more). However, lithium-sulfur batteries are environmentally friendly because they eliminate these pollutants and use non-toxic materials. Furthermore, sulfur, the cathode material, has the advantage of being abundant and inexpensive.

[0010] Meanwhile, in lithium-sulfur batteries, sulfur reduction and lithium metal oxidation occur during discharge. During this process, sulfur converts from a ring-shaped S8 to a linear lithium polysulfide (LiPS). These batteries exhibit a gradual discharge voltage until the lithium polysulfide is completely reduced to Li2S. However, during the charge / discharge process, lithium-sulfur batteries experience reduced charge / discharge efficiency, resulting in a shortened battery life. This shortened life of lithium-sulfur batteries can be attributed to a variety of factors, including electrolyte side reactions, lithium metal instability, and the accumulation of by-products on the cathode (e.g., lithium polysulfide leaching from the cathode).

[0011] Lithium-sulfur batteries, which use sulfur-based compounds as the positive electrode active material and alkali metals such as lithium as the negative electrode active material, suffer from the problem of lithium polysulfide leaching during charging and discharging. The lithium polysulfide leached from the positive electrode is transferred to the negative electrode, reducing the capacity of the lithium-sulfur battery and shortening its lifespan. Because lithium polysulfide leached from the positive electrode has high solubility in the electrolyte, it passes through the separator membrane via the electrolyte and unintentionally migrates to the negative electrode, resulting in a decrease in capacity due to irreversible loss of the positive electrode active material and a decrease in battery life due to the accumulation of sulfur particles on the lithium metal surface due to side reactions.

[0012] To solve the problem of reduced battery life due to lithium polysulfides, the industry has been conducting research into adding reaction-reducing substances to the negative electrode to prevent side reactions on the surface of lithium metal, but no significant results have been achieved. Summary of the Invention [Problem to be solved by the invention]

[0013] The problem to be solved by one embodiment of the present invention is to provide a block copolymer that can capture lithium polysulfides leached from the positive electrode and improve the life of lithium-sulfur batteries.

[0014] Another object of the present invention is to provide a crosslinked block copolymer produced by polymerizing the block copolymer.

[0015] Another problem to be solved by the present invention is to provide a sulfur-carbon composite that can capture lithium polysulfides leached from a positive electrode and improve the life of a lithium-sulfur battery.

[0016] Another object of the present invention is to provide a method for producing the sulfur-carbon composite. [Means for solving the problem]

[0017] To achieve the objects of the present invention, there are provided a block copolymer, a crosslinked block copolymer including the block copolymer, a sulfur-carbon composite, and a method for producing the sulfur-carbon composite, according to the following exemplary embodiments.

[0018] According to the first embodiment, a first block including a first repeating unit having a pyrene group at its terminal; and a second block comprising a second repeat unit having a cationic functional group.

[0019] According to the second embodiment, in the first embodiment, The molar ratio of the first block to the second block may be 1:99 to 99:1.

[0020] According to the third embodiment, in the first or second embodiment, The first repeating unit may be a reaction product between a carboxylic acid compound having the pyrene group at its terminal and an alcohol compound having a (meth)acrylate group.

[0021] According to the fourth embodiment, in any one of the first to third embodiments, The first repeating unit may be represented by the following Chemical Formula 1:

[0022] [ka]

[0023] In Chemical Formula 1, R 1 is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 20 carbon atoms, and R 2 is hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and n is 0 to 1,000,000.

[0024] According to the fifth embodiment, in any one of the first to fourth embodiments, The second repeat unit may include Formula 2:

[0025] [ka]

[0026] In Chemical Formula 2, R 3 is hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and R 4is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 20 carbon atoms, and R 5 Ha-NR 6 R 7 and R 6 and R 7 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

[0027] According to the sixth embodiment, in any one of the first to fifth embodiments, The first repeating unit is represented by the following Chemical Formula 3: The second repeating unit may be represented by the following Chemical Formula 4:

[0028] [ka]

[0029] [ka]

[0030] In Chemical Formula 3, n is 1 to 1,000,000; In Chemical Formula 4, m is 1 to 1,000,000.

[0031] According to the seventh embodiment, a first block copolymer and a second block copolymer having the same structure as the first block copolymer and crosslinked with the first block copolymer; The first block copolymer may be a crosslinked block copolymer according to any one of the first to sixth embodiments.

[0032] According to the eighth embodiment, in the seventh embodiment, The cationic functional groups contained in the first block copolymer and the cationic functional groups contained in the second block copolymer can be crosslinked with a crosslinking agent.

[0033] According to the ninth embodiment, a porous carbon material; a coating layer located on at least one surface of the porous carbon material and including the crosslinked block copolymer according to the seventh or eighth embodiment; a sulfur compound located on at least a portion of the surface of the porous carbon material, in the pores of the porous carbon material, and on the surface of the coating layer.

[0034] According to the tenth embodiment, in the ninth embodiment, The weight ratio of the porous carbon material to the crosslinked block copolymer may be 95:5 to 85:15.

[0035] According to the eleventh embodiment, in the ninth or tenth embodiment, The weight ratio of the porous carbon material coated with the crosslinked block copolymer to the sulfur compound may be 3:7 to 4:6.

[0036] According to the twelfth embodiment, The battery includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, The positive electrode may be the sulfur-carbon composite according to any one of the ninth to eleventh embodiments of the lithium-sulfur battery.

[0037] According to the thirteenth embodiment, Injecting the block copolymer according to any one of the first to sixth embodiments into a solution in which a porous carbon material is dispersed, thereby coating the block copolymer on at least one surface of the porous carbon material; cross-linking the block copolymer coated on the porous carbon material to form a cross-linked block copolymer; and supporting a sulfur compound on the porous carbon material coated with the crosslinked block copolymer.

[0038] According to the fourteenth embodiment, in the thirteenth embodiment, The cross-linked block copolymer may be formed by injecting a cross-linking agent into the porous carbon material coated with the block copolymer, followed by heat treatment.

[0039] According to the fifteenth embodiment, in the fourteenth embodiment, The cross-linking agent may include a dihalogenated alkane compound. [Effects of the Invention]

[0040] A sulfur–carbon composite according to one embodiment of the present invention comprises a crosslinked block copolymer, the crosslinked block copolymer comprising a first block including a first repeat unit having a terminal pyrene group and a second block including a second repeat unit having a cationic functional group.

[0041] The crosslinked block copolymer coating on the sulfur-carbon composite prevents lithium polysulfide leached from the positive electrode of the lithium-sulfur battery from being transferred to the negative electrode, thereby preventing the accumulation of sulfur particles on the surface of the lithium metal in the negative electrode, thereby maintaining the charge / discharge capacity of the lithium-sulfur battery and improving its lifespan.

[0042] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concept of the present invention, and the present invention should not be interpreted as being limited only to the matters described in the drawings. [Brief explanation of the drawings]

[0043] [Figure 1] 1 shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 2] 1 shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 3] 1 shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 4] 1 shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 5] 1 shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 6] 1 shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 7] 1 is a graph showing the results of evaluating the discharge capacity of a battery after charging and discharging at 25° C. [Figure 8] 1 is a graph showing the results of evaluating the discharge capacity of a battery after charging and discharging at 25° C. [Figure 9] 1 is a graph showing the results of evaluating the discharge capacity of a battery after charging and discharging at 25° C. [Figure 10] 1 is a graph showing the results of evaluating the discharge capacity of a battery after charging and discharging at 25° C. DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention will be described in more detail below.

[0045] The terms and words used in this specification and claims should not be interpreted limited to their ordinary and dictionary meanings, but should be interpreted in terms and concepts that correspond to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain his invention.

[0046] Throughout this specification, when a part is described as "comprising" or "having" a certain component, it does not mean that other components are excluded, but that other components may also be included, unless otherwise specified.

[0047] Furthermore, the term "about" used throughout this specification, when inherent manufacturing and material tolerances are given, is used to mean a numerical value or a value close to that numerical value, in order to prevent unconscionable infringers from unfairly using disclosure content in which exact or absolute numerical values ​​are mentioned to aid in the understanding of this application.

[0048] The present invention relates to a block copolymer, a crosslinked block copolymer containing the block copolymer, a sulfur-carbon composite, a method for manufacturing the sulfur-carbon composite, an electrochemical battery containing the same, and a method for manufacturing the same. In the present invention, the electrochemical battery may include any battery that performs an electrochemical reaction. Specifically, it includes all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitors. In particular, the electrochemical battery may be a secondary battery, and the secondary battery may be a lithium-ion secondary battery. Examples of the lithium-ion secondary battery include lithium-metal batteries, lithium-sulfur batteries, all-solid-state batteries, and lithium polymer batteries. Among these, lithium-sulfur batteries are preferred.

[0049] Lithium-sulfur batteries have attracted attention as next-generation secondary batteries due to their high discharge capacity and theoretical energy density, as well as the advantages of reducing battery manufacturing costs and being environmentally friendly, as sulfur, which is used as a cathode active material, is abundant and inexpensive.

[0050] In the present invention, the positive electrode active material includes a carbon-sulfur composite, and the carbon-sulfur composite includes a porous carbon material. In lithium-sulfur batteries, sulfur, which is a positive electrode active material, is a non-conductor, so to compensate for its low electrical conductivity, a sulfur-carbon composite is generally used, which is composited with a conductive carbon material.

[0051] According to one aspect of the present invention, a first block including a first repeating unit having a pyrene group at its terminal; and a second block comprising a second repeat unit having a cationic functional group.

[0052] According to one embodiment of the present invention, the molar ratio of the first block to the second block may be appropriately selected as needed. For example, the molar ratio may be 1:99 to 99:1. The weight-average molecular weight of the block copolymer may be appropriately selected as needed. For example, the weight-average molecular weight of the block copolymer may be 10 to 5,000,000.

[0053] According to one embodiment of the present invention, the first block may be derived from the first repeat unit, and the second block may be derived from the second repeat unit.

[0054] For example, the first block may be produced by chain transfer polymerization of the first repeating unit, and the second block may be produced by chain transfer polymerization of the second repeating unit, in which case the degrees of polymerization of the first block and the second block may each be 10 to 1,000,000.

[0055] According to one embodiment of the present invention, the first repeating unit may be a reaction product between a carboxylic acid compound having the pyrene group at its terminal and an alcohol compound having a (meth)acrylate group.

[0056] For example, the carboxylic acid compound having the pyrene group at its terminal can be represented by the following chemical formula 5:

[0057] [ka]

[0058] In Chemical Formula 5, R 1may be a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 20 carbon atoms.

[0059] For example, the carboxylic acid compound may be 1-pyrenebutyric acid. That is, in Formula 1, R 1 may be a propylene group having 3 carbon atoms.

[0060] For example, the alcohol compound having a (meth)acrylate group can be represented by the following chemical formula 6.

[0061] [ka]

[0062] In Chemical Formula 6, R 2 is hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and n can be 0 to 1,000,000.

[0063] For example, the alcohol compound may be poly(ethylene glycol) methyl ether methacrylate. That is, in Chemical Formula 6, R 2 can be hydrogen.

[0064] For example, the first repeating unit may be represented by the following Chemical Formula 7:

[0065] [ka]

[0066] According to one embodiment of the present invention, the cationic functional group may include a functional group having a nitrogen atom, and the cationic functional group may adsorb to polysulfide.

[0067] According to one embodiment of the present invention, the first repeat unit may include the following formula 8:

[0068] [ka]

[0069] In Chemical Formula 8, n is 1 to 1,000,000.

[0070] According to one embodiment of the present invention, the second repeat unit may include the following formula 9:

[0071] [ka]

[0072] In Chemical Formula 9, R 3 is hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and R 4 is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 20 carbon atoms, and R 5 Ha-NR 6 R 7 and R 6 and R 7 may each independently be hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

[0073] For example, the second repeating unit may be represented by the following Chemical Formula 10:

[0074] [ka]

[0075] In Chemical Formula 10, m can be 0 to 1,000,000.

[0076] According to one embodiment of the present invention, the block copolymer may be formed by polymerizing the first block and the second block by chain transfer polymerization. For example, the first block, the second block, a chain transfer agent (CTA), and a thermal initiator (e.g., azobisisobutyronitrile (AIBN)) may be dissolved in a dioxane solvent, and the solution may be polymerized at a high temperature (e.g., 80°C) after removing oxygen from the solution. For example, 4-cyano-4-(((tridecylthio)carbonothioyl)thio)pentanoic acid may be used as the chain transfer agent. The block copolymer may then be produced by precipitation and purification with diethyl ether.

[0077] According to one embodiment of the present invention, the block copolymer comprising the first block and the second block may be represented by the following Chemical Formula 11:

[0078] [ka]

[0079] In Chemical Formula 11, m, n, and k can each be 0 to 1,000,000.

[0080] According to another aspect of the present invention, a first block copolymer and a second block copolymer having the same structure as the first block copolymer and crosslinked with the first block copolymer; The first block copolymer may be a crosslinked block copolymer, which may be any one of the block copolymers described above.

[0081] According to an embodiment of the present invention, the crosslinked block copolymer may be obtained by crosslinking the first block copolymer with the second block copolymer, specifically, by crosslinking the cationic functional groups of the first block copolymer with the cationic functional groups of the second block copolymer using a crosslinking agent. The type of the crosslinking agent is not particularly limited, but may include, for example, a dihalogenated alkane compound (e.g., diiodobutane).

[0082] According to yet another aspect of the present invention, a porous carbon material; a coating layer located on at least one surface of the porous carbon material, the coating layer comprising the crosslinked block copolymer described above; a sulfur compound located on at least a portion of the surface of the porous carbon material, in the pores of the porous carbon material, and on the surface of the coating layer.

[0083] The porous carbon material includes a plate-shaped carbon material, and the specific surface area of ​​the porous carbon material is 1,000 m 2 / g or more, and the pore volume of the porous carbon material is 4 cm 3 / g or more.

[0084] The porous carbon material has a large specific surface area to increase the number of active sites where sulfur can participate in oxidation / reduction reactions, and a large pore volume to facilitate sulfur loading and ensure ion diffusion paths.

[0085] The sulfur-carbon composite includes a porous carbon material as a support for supporting a sulfur-containing compound. Specifically, the sulfur-carbon composite includes a plate-like porous carbon material as the porous carbon material. The plate-like porous carbon material may include, for example, graphene, graphene oxide, reduced graphene oxide (rGO), or a mixture of two or more thereof.

[0086] In an embodiment of the present invention, the plate-shaped porous carbon material may include reduced graphene oxide alone.

[0087] The porous carbon material is 1,000 m 2 Specifically, the upper limit of the BET specific surface area of ​​the porous carbon material is not particularly limited, but it may be, for example, 1,000 m 2 / g or more 1,500m 2 / g or less, 1,300m 2 / g or less, 1,200m 2 / g or less, 1,100m 2 / g or less, 1,050m 2 The sulfur-carbon composite according to one embodiment of the present invention has a large number of micropores on the outer surface and / or inside thereof, and thus has an advantage of a very large specific surface area.

[0088] The BET specific surface area is measured by the BET method and may be a value measured by a known method for measuring a BET specific surface area. For example, the BET specific surface area may be a value calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77 K) using a BELSORP-max manufactured by BEL Japan Co., Ltd.

[0089] The porous carbon material is 4 cm 3 Specifically, the upper limit of the pore volume of the porous carbon material is not particularly limited, but it may be, for example, 4 cm 3 / g or more 15cm 3 / g or less, 6cm 3 / g or more 10cm 3 / g or less, 6cm 3 / g or more 8cm 3 / g or less, or 6.5cm 3 / g or more 7.5cm 3 The pore volume may be a value calculated and measured through, for example, N adsorption isotherm analysis obtained based on the adsorption of liquid nitrogen.

[0090] As described above, the porous carbon material in the sulfur-carbon composite according to one embodiment of the present invention contains a large number of micropores for supporting the sulfur-containing compound.

[0091] In one embodiment of the present invention, the porous carbon material includes a plurality of micropores on the outer surface and inside thereof, and the micropores include mesopores having a diameter of 1 nm or more and less than 50 nm, and macropores having a diameter of 50 nm or more and 200 nm or less. In one embodiment of the present invention, the porous carbon material preferably has the mesopores and macropores uniformly distributed.

[0092] The diameter of the micropores can be measured by any known method in the art for measuring the diameter of pores in porous materials, and the measurement method is not particularly limited. For example, the average diameter of the micropores can be measured using a scanning electron microscope (SEM), a field emission electron microscope, or a laser diffraction method. Measurement using the laser diffraction method can be performed using, for example, a commercially available laser diffraction particle sizer (e.g., Microtrac MT3000).

[0093] In another embodiment of the present invention, the average diameter (D50) of all pores of the porous carbon material may be, but is not limited to, 20 nm to 25 nm, and the average diameter (D50) refers to the diameter at the 50% point of the cumulative number distribution according to the diameter.

[0094] In the present invention, the porous carbon material having the above-mentioned properties contains a sulfur compound on the outer surface and at least part of the interior of the pores.

[0095] The sulfur compound may be used without limitation as long as it can be used as a positive electrode active material in a lithium-sulfur secondary battery. For example, the sulfur compound may be inorganic sulfur (S), lithium polysulfide (LiS), or the like. n , 1≦n≦8), carbon-sulfur polymer (C2S x ) m , 2.5≦x≦50, 2≦m), or mixtures thereof.

[0096] The sulfur compound may be contained in the sulfur-carbon composite by physical adsorption onto the porous carbon material or by chemical bonding, such as covalent bonding or van der Waals bonding, between the sulfur element and carbon in the porous carbon material.

[0097] In one embodiment of the present invention, the porous carbon material and the sulfur compound in the sulfur-carbon composite may be present in a weight ratio of, for example, 1:9 to 9:1, specifically, 1:9 to 5:5, 1:9 to 4:6, 1:9 to 3:7, or 1:9 to 1.5:8.5. When the weight ratio of the porous carbon material to the sulfur compound in the sulfur-carbon composite is within the above range, the high content of the sulfur compound enhances the dynamic activity of the sulfur-carbon composite, while also improving the electrical conductivity of the porous carbon material. However, the present invention is not limited thereto.

[0098] In another embodiment of the present invention, the content of the sulfur compound in the sulfur-carbon composite may be, for example, 10 wt% or more, specifically 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 85 wt% or more, based on the total weight of the sulfur-carbon composite. Furthermore, within the above-mentioned range, the content may be 50 wt% to 90 wt%, specifically 60 wt% to 90 wt%, 70 wt% to 90 wt%, or 85 wt% to 90 wt% based on the total weight of the sulfur-carbon composite. When the content of the sulfur compound in the sulfur-carbon composite is within the above-mentioned range, the high content of the sulfur compound is advantageous in terms of enhancing the dynamic activity of the sulfur-carbon composite and improving the electrical conductivity of the porous carbon material, but the present invention is not limited thereto.

[0099] In one embodiment of the present invention, the average particle size (D50) of the sulfur-carbon composite may be, for example, 0.5 μm to 200 μm, 0.5 μm to 200 μm, 1 μm to 150 μm, or 10 μm to 150 μm. The particle size of the sulfur-carbon composite may be measured using a scanning electron microscope (SEM), a field emission electron microscope, or a laser diffraction method. The measurement using the laser diffraction method may be performed using, for example, a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT3000). The average particle size (D50) refers to the particle size at the 50% point of the cumulative number distribution according to particle size.

[0100] In one embodiment of the present invention, the sulfur-carbon composite has a Raman peak intensity ratio (I G / I D The ratio of I to I may be 1 or less. G / I D If the ratio exceeds 1, the surface crystallinity of the sulfur-carbon composite may be high, which may result in a decrease in the efficiency of the composite with the sulfur-containing compound or the conversion reaction of lithium polysulfide, but this is not limited to the above.

[0101] The Raman peak intensity ratio is calculated from the spectrum of the carbon composite obtained by Raman spectroscopy. G and I D In the resulting spectrum, I G means the peak of the crystalline part (G-peak, 1573 / cm), and I D means the peak of the amorphous part (D-peak, 1309 / cm). Therefore, in this case, I G / I D The smaller the ratio, the lower the crystallinity.

[0102] In one embodiment of the present invention, the sulfur-carbon composite may be formed by mixing the porous carbon material and a sulfur compound and then heat-treating the mixture; however, the manufacturing method of the present invention is not limited thereto.

[0103] The sulfur-carbon composite of the present invention includes a plate-like carbon material having a large specific surface area and pore volume, which not only increases the sulfur loading but also provides a large number of active sites for the sulfur oxidation / reduction reaction. Therefore, when used in the positive electrode of a lithium-sulfur battery, the battery efficiency and energy density can be improved. However, the mechanism of the present invention is not limited to this.

[0104] In one embodiment of the present invention, the coating layer may include the crosslinked block copolymer. For example, the weight ratio of the porous carbon material to the crosslinked block copolymer may be 95:5 to 85:15. Also, the weight ratio of the porous carbon material coated with the crosslinked block copolymer to the sulfur compound may be 3:7 to 4:6.

[0105] According to yet another aspect of the present invention, Injecting the block copolymer into a solution in which the porous carbon material is dispersed to coat at least one surface of the porous carbon material with the block copolymer; cross-linking the block copolymer coated on the porous carbon material to form a cross-linked block copolymer; and supporting sulfur on the porous carbon material coated with the crosslinked block copolymer.

[0106] In one embodiment of the present invention, the porous carbon material (e.g., Ketjen Black (KB)) and chloride (e.g., FeCl3) may be dispersed in a solvent. For example, the solvent is not particularly limited as long as it can dissolve or disperse the compound, and examples thereof include chlorine-based solvents such as chloroform, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, and o-dichlorobenzene; ether-based solvents such as tetrahydrofuran and dioxane; aromatic hydrocarbon-based solvents such as toluene, xylene, trimethylbenzene, and mesitylene; aliphatic hydrocarbon-based solvents such as cyclohexane, methylcyclohexane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; ketone-based solvents such as acetone, methyl ethyl ketone, and cyclohexanone; ester-based solvents such as ethyl acetate, butyl acetate, and ethyl cellosolve; and ethylene glycol. The solvent may be a polyhydric alcohol or a derivative thereof such as ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, dimethoxyethane, propylene glycol, diethoxymethane, triethylene glycol monoethyl ether, glycerin, or 1,2-hexanediol; an alcohol-based solvent such as methanol, ethanol, propanol, isopropanol, or cyclohexanol; a sulfoxide-based solvent such as dimethyl sulfoxide; an amide-based solvent such as N-methyl-2-pyrrolidone or N,N-dimethylformamide; a benzoate-based solvent such as butyl benzoate or methyl-2-methoxybenzoate; tetralin; or a solvent such as 3-phenoxytoluene.

[0107] Next, the block copolymer may be poured into the solution containing the dispersed porous carbon material, and then coated at room temperature for 24 hours. For example, the weight ratio of the porous carbon material to the block copolymer may be 95:5 to 85:15.

[0108] Thereafter, a crosslinking agent (e.g., a dihalogenated alkane compound such as diiodobutane) is poured into the solution in which the porous carbon material coated with the block copolymer is dispersed, followed by heat treatment at about 45°C for 24 hours, thereby crosslinking the block copolymer in the porous carbon material.

[0109] Then, the porous carbon material coated with the crosslinked block copolymer may be loaded with a sulfur compound and then heat-treated to prepare the sulfur-carbon composite. For example, the weight ratio of the porous carbon material coated with the crosslinked block copolymer to the sulfur compound may be 3:7 to 4:6.

[0110] The crosslinked block copolymer coated on the porous carbon material prevents lithium polysulfide leached from the positive electrode of the lithium-sulfur battery from being transferred to the negative electrode, thereby preventing the accumulation of sulfur particles on the surface of the lithium metal in the negative electrode, thereby maintaining the charge / discharge capacity of the lithium-sulfur battery and improving its lifespan.

[0111] The present invention will be described in detail below with reference to examples to aid in understanding the present invention. However, the examples according to the present invention can be modified into many other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0112] Example 1 Production of block copolymers 1) Preparation of the first monomer: 1-pyrenebutyric acid (PBA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) were reacted in a toluene solvent at 110°C under the catalyst of p-toluenesulfonic acid (pTsOH) to synthesize PEGMA-PBA (hereinafter referred to as PP). The synthesized PP was purified by extraction three times with HO / MC (methylene chloride).

[0113] The specific synthesis mechanism is shown in Figure 1, and the structure of the synthesized monomer is 1The results were confirmed by 1 H NMR and are shown in Figure 2.

[0114] 2) Preparation of second monomer: Dimethylaminoethyl acrylate (DMAEMA), a chain transfer agent (CTA, 4-cyano-4-(((tridecylthio)carbonothioyl)thio)pentanoic acid), and AIBN were dissolved in dioxane solvent, and the solution was subjected to freeze-pump-thaw three times to remove oxygen from the solution. The deoxygenated solution was polymerized at 80°C. The crude product after polymerization was purified by precipitation three times in hexane to obtain poly(dimethylamino)ethyl methacrylate (PDMAEMA).

[0115] The specific synthesis mechanism is shown in Figure 3, and the structure of the synthesized monomer is 1 The results were confirmed through 1 H NMR and GPC analysis, and are shown in Figure 4.

[0116] 3) Preparation of block copolymer: The first monomer, second monomer (first monomer:second monomer = 1:1 (molar ratio)) prepared as above, CTA (4-cyano-4-(((tridecylthio)carbonothioyl)thio)pentanoic acid), and AIBN were dissolved in dioxane solvent, and the solution was subjected to freeze-pump-thaw three times to remove oxygen. The deoxygenated solution was polymerized at 80°C. The crude product after polymerization was purified by precipitation three times in diethyl ether to obtain PDbPP.

[0117] The specific synthesis mechanism is shown in Figure 5, and the structure of the synthesized PDbPP is 1 The results were confirmed through 1 H NMR and GPC analysis, and are shown in Figure 6.

[0118] Production of sulfur carbon composites 1) Disperse Ketjen Black (KB) and FeCl3 in chloroform solvent by sonication for 3 hours.

[0119] 2) After dissolving PDbPP (10 wt% relative to KB) in chloroform, add it dropwise to the solution in which KB is dispersed and stir at room temperature for 24 hours to coat it.

[0120] 3) Diiodobutane is added dropwise to the solution in which the PDbPP-coated KB is dispersed, and the solution is then reacted at 45°C for 24 hours to crosslink the coated PDbPP to produce CPDbPP10-KB.

[0121] 4) CPDbPP10-KB and sulfur are ground and mixed (CPDbPP10-KB:S=7:3 (w / w)) and heat-treated at 155°C for 30 minutes to load sulfur and produce CPDbPP10-KB-S.

[0122] positive electrode As the positive electrode active material, a sulfur-carbon composite (CPDbPP10-KB-S) was used, in which a sulfur compound was supported on Ketjen black coated with the above-mentioned crosslinked block copolymer.

[0123] The sulfur-carbon composite, PAA binder (poly(acrylic acid)), and carbon conductive material were mixed in a weight ratio of 85:10:5, and 0.5 wt% of PVA dispersant was added to prepare a cathode slurry with a solid concentration of 18 wt%. The cathode slurry was then uniformly coated on aluminum foil to a thickness of 400 μm and dried at 50°C to form a cathode. The weight ratio of the crosslinked block copolymer to the cathode was 8.5 wt%.

[0124] Separator, negative electrode and electrolyte A polyethylene porous film (Celgard separator) was used as the separator, lithium metal was used as the anode, and 1.0M LiNO3 was added to a mixed solvent of 1,3-dioxolane (DOL) and 1,2-dimethyl ether in a volume ratio (v / v) of 50:50 to prepare an electrolyte for a lithium-sulfur secondary battery.

[0125] <Comparative Example 1> positive electrode A positive electrode was prepared in the same manner as in Example 1, except that a sulfur-carbon composite prepared by mixing Ketjen black and a sulfur compound at a weight ratio of 3:7 was used as the positive electrode active material.

[0126] Separator, negative electrode and electrolyte A separator, a negative electrode, and an electrolyte were prepared in the same manner as in Example 1.

[0127] <Comparative Example 2> positive electrode The positive electrode active material used was a sulfur-carbon composite prepared by (1) supporting a sulfur compound on Ketjen black, (2) coating the block copolymer onto the sulfur-compound-supported Ketjen black, and (3) crosslinking the block copolymer to form a crosslinked block copolymer. The sulfur-carbon composite, PAA binder, and carbon conductive material were mixed in a weight ratio of 85:10:5, and 0.5 wt% of PVA dispersant was added to prepare a positive electrode slurry with a solids concentration of 18 wt%. The positive electrode slurry was then uniformly coated on aluminum foil to a thickness of 400 μm and dried at 50°C to form a positive electrode. The weight ratio of the crosslinked block copolymer to the positive electrode was 3 wt%.

[0128] Separator, negative electrode and electrolyte A separator, a negative electrode, and an electrolyte were prepared in the same manner as in Example 1.

[0129] <Comparative Example 3> positive electrode A positive electrode was prepared in the same manner as in Comparative Example 2, except that the weight ratio of the Ketjen black coated with the crosslinked block copolymer and the sulfur compound was 1:9 (CPDbPP10-KB:S=1:9 (w / w)).

[0130] Separator, negative electrode and electrolyte A separator, a negative electrode, and an electrolyte were prepared in the same manner as in Example 1.

[0131] <Comparative Example 4> positive electrode A positive electrode was prepared in the same manner as in Comparative Example 2, except that the weight ratio of the crosslinked block copolymer to the positive electrode was 1 wt %.

[0132] Separator, negative electrode and electrolyte A separator, a negative electrode, and an electrolyte were prepared in the same manner as in Example 1.

[0133] <Comparative Example 5> positive electrode A positive electrode was prepared in the same manner as in Comparative Example 2, except that the weight ratio of the crosslinked block copolymer to the positive electrode was 5 wt %.

[0134] Separator, negative electrode and electrolyte A separator, a negative electrode, and an electrolyte were prepared in the same manner as in Example 1.

[0135] FIG. 7 is a graph showing the results of evaluating the discharge capacity when charging and discharging were performed under the following conditions at 25° C.

[0136] Evaluation device: WBSC3000 battery cycler (manufactured by WonA Tech) Current density: 0.2C rate Referring to FIG. 7, the lithium-sulfur battery according to Example 1 exhibited a higher discharge capacity than the lithium-sulfur battery according to Comparative Example 1 during the 1st to 100th cycles.

[0137] FIG. 8 is a graph showing the results of evaluating the discharge capacity when charging and discharging were performed under the following conditions at 25° C.

[0138] Evaluation device: WBSC3000 battery cycler (manufactured by WonA Tech) Current density: 1C rate Referring to FIG. 8, the lithium-sulfur battery according to Example 1 exhibited a higher discharge capacity than the lithium-sulfur battery according to Comparative Example 1 between 40 and 160 cycles.

[0139] 9 and 10 are graphs showing the results of evaluating the discharge capacity when charging and discharging were performed at 25° C. under the following conditions:

[0140] Evaluation device: WBSC3000 battery cycler (manufactured by WonA Tech) Current density: 0.2C rate 9 and 10, as can be seen from FIG. 9, the lithium-sulfur battery according to Example 1 exhibited a higher discharge capacity than the lithium-sulfur batteries according to Comparative Examples 1 and 2 from 1 to 50 cycles.

[0141] In other words, it can be seen that first forming the coating layer on the porous carbon material and then supporting the sulfur compound improves the coating properties of the coating layer and is advantageous in ensuring discharge capacity compared to not forming a coating layer or forming a coating layer after supporting sulfur.

[0142] Meanwhile, referring to FIG. 10, it can be seen that Comparative Example 2 is advantageous in securing discharge capacity compared to Comparative Examples 1, 4, and 5. However, as seen in FIG. 9, Comparative Example 2 is inferior to Example 1 in which the coating layer is formed first and then the sulfur compound is supported.

Claims

1. a first block including a first repeating unit having a pyrene group at its terminal; a second block comprising a second repeat unit having a cationic functional group.

2. 2. The block copolymer of claim 1, wherein the molar ratio of the first block to the second block is from 1:99 to 99:

1.

3. The block copolymer according to claim 1 , wherein the first repeating unit is a reaction product of a carboxylic acid compound having the pyrene group at its terminal and an alcohol compound having a (meth)acrylate group.

4. The first repeating unit is represented by the following formula 1: 【Chemical 1】 is expressed as In Chemical Formula 1, R １ is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 20 carbon atoms; R ２ 2. The block copolymer of claim 1, wherein n is hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and n is 0 to 1,000,000.

5. The second repeating unit is represented by the following formula 2: 【Chemistry 2】 Including, In Chemical Formula 2, R ３ is hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and R ４ is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 20 carbon atoms; R ５ Ha-NR ６ R ７ and R ６ and R ７ and each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

6. The first repeating unit has the following formula 3: 【Chemistry 3】 In Chemical Formula 3, n is 1 to 1,000,000; The second repeating unit has the following formula 4: 【Chemistry 4】 2. The block copolymer according to claim 1, wherein m is 1 to 1,000,000 in Chemical Formula 4.

7. a first block copolymer and a second block copolymer having the same structure as the first block copolymer and crosslinked with the first block copolymer; A crosslinked block copolymer, wherein the first block copolymer is a block copolymer according to claim 1 .

8. The crosslinked block copolymer according to claim 7 , wherein the cationic functional groups contained in the first block copolymer and the cationic functional groups contained in the second block copolymer are crosslinked by a crosslinking agent.

9. a porous carbon material; a coating layer located on at least one surface of the porous carbon material, the coating layer comprising the crosslinked block copolymer of claim 7; a sulfur compound located at least partially on the surface of the porous carbon material, in the pores of the porous carbon material, and on the surface of the coating layer.

10. 10. The sulfur-carbon composite according to claim 9, wherein a weight ratio of the porous carbon material to the crosslinked block copolymer is from 95:5 to 85:

15.

11. 10. The sulfur-carbon composite according to claim 9, wherein a weight ratio of the porous carbon material coated with the crosslinked block copolymer to the sulfur compound is 3:7 to 4:

6.

12. The battery includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, A lithium-sulfur battery, wherein the positive electrode comprises the sulfur-carbon composite of claim 9.

13. Injecting the block copolymer according to any one of claims 1 to 6 into a solution in which a porous carbon material is dispersed, thereby coating the block copolymer on at least one surface of the porous carbon material; cross-linking the block copolymer coated on the porous carbon material to form a cross-linked block copolymer; and supporting a sulfur compound on the porous carbon material coated with the crosslinked block copolymer.

14. 14. The method for producing a sulfur-carbon composite according to claim 13, wherein the crosslinked block copolymer is formed by injecting a crosslinking agent into the porous carbon material coated with the block copolymer, followed by heat treatment.

15. 15. The method for producing a sulfur-carbon composite according to claim 14, wherein the cross-linking agent comprises a dihalogenated alkane compound.

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