Block copolymer, crosslinked block copolymer containing the block copolymer, sulfur-carbon composite, and method for producing the 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 improving battery life by capturing polysulfide eluted from the positive electrode, and a secondary battery containing the block copolymer.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0110368, filed on 31 August 2022, and all content disclosed in the specification and drawings of said application is incorporated herein. [Background technology]

[0003] As technological development and demand for mobile devices increase, the demand for rechargeable batteries as an energy source is surging. Among rechargeable batteries, lithium-ion batteries, which have high energy density and operating potential, long cycle life, and low self-discharge rate, have become commonplace and are widely used.

[0004] Furthermore, in recent years, with growing concern for environmental issues, research into electric vehicles (EVs) and hybrid electric vehicles (HEVs) that can replace fossil fuel-using vehicles such as gasoline and diesel vehicles, which are one of the main causes of air pollution, is actively being conducted. As a power source for such electric vehicles and hybrid electric vehicles, lithium-ion batteries, which have high energy density, high discharge voltage, and output stability, are mainly being researched and used.

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

[0006] Currently, the lithium-ion battery market is dominated by technology based on the pairing of lithium cobalt oxide (LiCoO2) as the positive electrode and graphite as the negative electrode. While most other types of batteries (Ni-CD, Ni-MH, etc.) have a rated voltage of 1.5V, lithium-ion batteries have a rated voltage of approximately 3.6V. Their volumetric and mass energy densities are approximately 300-500 Wh / l and 160-200 Wh / kg, respectively. This is the highest level among currently available batteries. Lithium-ion batteries also have low self-discharge and a long lifespan (500 or 1000 cycles). Despite these remarkable performance characteristics, all lithium-ion batteries are currently expected to have leveled off in terms of performance, and the prospects for further improvement are limited.

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

[0008] Lithium-sulfur batteries, like conventional lithium-ion secondary batteries, operate on lithium ions moving within an electrolyte interposed between the positive and negative electrodes. 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 where lithium ions penetrate between the molecules of the electrode active material to deform the electrode structure and store energy. Therefore, lithium-sulfur batteries have less constraint on electrode structure compared to conventional lithium-ion secondary batteries and can theoretically have a larger capacity for the same volume. Due to these characteristics, in a lithium-sulfur battery composed of a sulfur positive electrode and a lithium metal negative electrode, assuming that monomeric sulfur (S8) with a ring structure completely reacts to lithium polysulfide (Li2S), the theoretical capacity becomes 1,675 mAh / g and the theoretical energy density becomes 2,600 Wh / kg, which is 3 to 6 times higher than other conventional battery systems (Ni / MH battery: 450 Wh / kg, Li / FeS: 480 Wh / kg, Li / MnO2: 1,000 Wh / kg, Na / S: 800 Wh / kg).

[0009] On the one hand, in conventional transition metal oxide-based lithium-ion secondary batteries, oxides of nickel (Ni), cobalt (Co), and manganese (Mn) having a density higher than that of heavy metals (metals with a density of 5 g / mL or more) are used for the positive electrode, so they are evaluated as batteries containing heavy metal pollutant substances. However, lithium-sulfur batteries exclude such pollutant substances and use non-toxic materials, so they can be said to be environmentally friendly. In addition, sulfur, which is the positive electrode material, has the advantages of being rich in resources and inexpensive.

[0010] On the other hand, in a lithium-sulfur battery, a reduction reaction of sulfur and an oxidation reaction of lithium metal occur during discharge. At this time, sulfur forms lithium polysulfide (LiPS) with a linear structure from S8 with a ring structure. Such a lithium-sulfur battery is characterized by showing a stepwise discharge voltage until the lithium polysulfide is completely reduced to Li2S. However, in the charging and discharging process of a lithium-sulfur battery, the charging / discharging efficiency decreases and the battery life deteriorates. The reasons for the deterioration of the lithium-sulfur battery life are diverse, such as side reactions of the electrolyte, instability of lithium metal, and deposition of positive electrode by-products (for example, elution of lithium polysulfide from the positive electrode).

[0011] That is, a lithium-sulfur battery that uses a sulfur-based compound as the positive electrode active material and an alkali metal such as lithium as the negative electrode active material has a problem that lithium polysulfide elution occurs during charging and discharging, and the lithium polysulfide eluted from the positive electrode is transmitted to the negative electrode, reducing the capacity of the lithium-sulfur battery, thereby reducing the life of the lithium-sulfur battery. That is, since the lithium polysulfide eluted from the positive electrode has a high solubility in the electrolyte, it passes through the separator through the electrolyte and undergoes an unintended movement to the negative electrode side, resulting in a decrease in capacity due to an irreversible loss of the positive electrode active material and accumulation of sulfur particles on the lithium metal surface due to side reactions, thereby reducing the battery life.

[0012] To solve the problem of reduced lifespan due to lithium polysulfide, in the industry, research has been conducted, such as adding reaction-inhibiting substances to the negative electrode so that side reactions do not occur on the surface of lithium metal, but no significant results have been achieved.

Summary of the Invention

Problems to be Solved by the Invention

[0013] One problem to be solved by an aspect of the present invention is to provide a block copolymer that can capture lithium polysulfide eluted from the positive electrode and improve the lifespan of a lithium-sulfur battery.

[0014] Another problem to be solved by an aspect of the present invention is to provide a crosslinked block copolymer produced by polymerizing the block copolymer.

[0015] Yet another problem to be solved by an aspect of the present invention is to provide a sulfur-carbon composite that can capture lithium polysulfide eluted from the positive electrode and improve the lifespan of a lithium-sulfur battery.

[0016] Still another problem to be solved by an aspect of the present invention is to provide a method for producing the sulfur-carbon composite.

Means for Solving the Problems

[0017] To solve the problems of the present invention, there are provided a block copolymer of the following embodiments, a crosslinked block copolymer containing the block copolymer, a sulfur-carbon composite, and a method for producing the sulfur-carbon composite.

[0018] According to the first embodiment, a first block containing a first repeating unit having a pyrene group at the end, and a second block containing a second repeating unit having a cationic functional group, are provided as a block copolymer. [[ID=​​According to the second example, in the first example, The molar ratio of the first block to the second block can be between 1:99 and 99:1.

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

[0021] According to the fourth example of manifestation, in any one of the first to third examples of manifestation, The first repeating unit can be represented by the following chemical formula 1.

[0022] [ka]

[0023] In chemical formula 1, R 1 R is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an allylene group having 6 to 20 carbon atoms. 2 n is 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, and n is between 0 and 1,000,000.

[0024] According to the fifth example of manifestation, in any one of the first to fourth examples of manifestation, The second repeating unit may include the following chemical formula 2.

[0025] [ka]

[0026] In chemical formula 2, R 3 R 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. 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 is -NR 6 R 7 where R 6 and R 7 are each independently 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. <同じく、

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

[0028]

Chemical formula

[0029]

Chemical formula

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

[0031] According to the seventh embodiment, a crosslinked block copolymer is provided that includes a first block copolymer and a second block copolymer having the same structure as the first block copolymer and crosslinked to the first block copolymer. The first block copolymer is the block copolymer described in 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 example, Porous carbon material, A coating layer located on at least one surface of the porous carbon material, comprising a crosslinked block copolymer according to the 7th embodiment or the 8th embodiment, A sulfur-carbon composite is provided, comprising a sulfur compound located on the surface of the porous carbon material, within the pores of the porous carbon material, and on at least a portion of the surface of the coating layer.

[0034] According to the 10th example, in the 9th example, The weight ratio of the porous carbon material to the crosslinked block copolymer can be 95:5 to 85:15.

[0035] According to the 11th embodiment, in the 9th embodiment or the 10th 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 12th example, It includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, The lithium-sulfur battery is provided in which the positive electrode is a sulfur-carbon composite as described in any one of the 9th to 11th embodiments.

[0037] According to the 13th example, The steps include: injecting a block copolymer described in any one of the first to sixth embodiments into a solution in which a porous carbon material is dispersed, thereby coating the block copolymer onto at least one surface of the porous carbon material; The steps include crosslinking the block copolymer coated on the porous carbon material to form a crosslinked block copolymer, A method for producing a sulfur-carbon composite is provided, comprising the step of supporting a sulfur compound on a porous carbon material coated with the aforementioned crosslinked block copolymer.

[0038] According to the 14th embodiment example, in the 13th embodiment example, The crosslinked block copolymer can be formed by injecting a crosslinking agent into the porous carbon material coated with the block copolymer and then heat-treating it.

[0039] According to the 15th example of implementation, in the 14th example of implementation, The crosslinking agent may include a dihalogenated alkane compound. [Effects of the Invention]

[0040] A sulfur-carbon composite according to one aspect of the present invention comprises a crosslinked block copolymer, the crosslinked block copolymer being produced from a block copolymer comprising a first block containing a first repeating unit having a pyrene group at its terminus, and a second block containing a second repeating unit having a cationic functional group.

[0041] By coating the sulfur-carbon composite with the cross-linked block copolymer, lithium polysulfide leached from the positive electrode of the lithium-sulfur battery is prevented from being transferred to the negative electrode. Therefore, the accumulation of sulfur particles on the surface of the lithium metal of the negative electrode is prevented, thereby maintaining the charge and discharge capacity of the lithium-sulfur battery and improving its battery life.

[0042] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention. The invention shall not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0043] [Figure 1] This shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 2] This shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 3] This shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 4] This shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 5] This shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 6] This shows the results of confirming the synthesis mechanism and synthesized structure of the monomer and block copolymer produced in Example 1. [Figure 7] This graph shows the evaluation of the battery's discharge capacity after charging and discharging at 25°C. [Figure 8] This graph shows the evaluation of the battery's discharge capacity after charging and discharging at 25°C. [Figure 9] This graph shows the evaluation of the battery's discharge capacity after charging and discharging at 25°C. [Figure 10] This graph shows the evaluation of the battery's discharge capacity after charging and discharging at 25°C. [Modes for carrying out the invention]

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

[0045] Terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary and dictionary meanings, but rather in a manner and concept corresponding to the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0046] Throughout this specification, when a part "includes" or "has" a component, unless otherwise specified, it does not exclude other components, but rather means that it may further include other components.

[0047] Furthermore, the term “about” as used throughout this specification is used, either numerically or in a sense close to numerically, when manufacturing and material tolerances specific to the meaning referred to are presented, to prevent unscrupulous infringers from unfairly using disclosures that refer to precise or absolute numerical values ​​to aid in understanding the present 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 producing the sulfur-carbon composite, an electrochemical battery containing the same, and a method for producing the same. In the present invention, the electrochemical battery may include any battery that performs an electrochemical reaction. Specifically, this includes all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors such as supercapacitor elements. In particular, the electrochemical battery may be a secondary battery, and the secondary battery may be a lithium-ion secondary battery. Examples of lithium-ion secondary batteries include lithium-metal batteries, lithium-sulfur batteries, all-solid-state batteries, and lithium polymer batteries, with lithium-sulfur batteries being preferred.

[0049] Lithium-sulfur batteries are attracting attention as a next-generation rechargeable battery not only because they have high discharge capacity and theoretical energy density compared to many other rechargeable batteries, but also because sulfur, which is used as the positive electrode active material, is abundant and inexpensive, thus reducing the manufacturing cost of the battery and making them environmentally friendly.

[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 the positive electrode active material, is an insulator, so a sulfur-carbon composite, which is a compound of sulfur with a conductive carbon material, is generally used to compensate for its low electrical conductivity.

[0051] According to one aspect of the present invention, A first block comprising a first repeating unit having a pyrene group at its terminus, A block copolymer is provided comprising a second block containing a second repeating 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 can 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 can also 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 repeating unit, and the second block may be derived from the second repeating 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 this case, the degree of polymerization of the first and second blocks may be 10 to 1,000,000, respectively.

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

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

[0057] [ka]

[0058] In chemical formula 5, R 1This can be a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an allylene group having 6 to 20 carbon atoms.

[0059] For example, the carboxylic acid compound may be 1-pyrenebutyric acid. That is, in chemical formula 1, R 1 This can 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 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 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 It can be hydrogen.

[0064] For example, the first repeating unit can 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. The cationic functional group may adsorb to a polysulfide.

[0067] According to one embodiment of the present invention, the first repeating unit may include the following chemical formula 8.

[0068] [ka]

[0069] In chemical formula 8, n ranges from 1 to 1,000,000.

[0070] According to one embodiment of the present invention, the second repeating unit may include the following chemical formula 9.

[0071] [ka]

[0072] In chemical formula 9, R 3 R 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. 4 R is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an allylene group having 6 to 20 carbon atoms. 5 -NR 6 R 7 And R 6 and R 7 Each of these can independently be hydrogen, a C1-C10 alkyl group, a C3-C10 cycloalkyl group, or a C6-C20 aryl group.

[0073] For example, the second repeating unit can be represented by the following chemical formula 10.

[0074] [ka]

[0075] In chemical formula 10, m can range from 0 to 1,000,000.

[0076] According to one embodiment of the present invention, the block copolymer can 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)) can be dissolved in a dioxane solvent, oxygen in the solution can be removed, and then polymerized at a high temperature (e.g., 80°C). For example, 4-cyano-4-(((tridecylthio)carbonothio)thio)pentanoic acid can be used as the chain transfer agent. The block copolymer can 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 range from 0 to 1,000,000.

[0080] According to another aspect of the present invention, The present invention comprises a first block copolymer and a second block copolymer having the same structure as the first block copolymer and being crosslinked with the first block copolymer. The first block copolymer is provided as a crosslinked block copolymer which is one of the block copolymers described above.

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

[0082] According to yet another aspect of the present invention, Porous carbon material, A coating layer located on at least one surface of the porous carbon material, comprising the crosslinked block copolymer described above, A sulfur-carbon composite is provided, comprising a sulfur compound located on the surface of the porous carbon material, within the pores of the porous carbon material, and on at least a portion of 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 m². 2 The amount is 1 / g or more, and the pore volume of the porous carbon material is 4 cm³. 3 It may be more than / g.

[0084] The porous carbon material is characterized by having a large specific surface area in order to increase the number of active sites on which sulfur can participate in oxidation / reduction reactions. Furthermore, the porous carbon material is characterized by having a large pore volume in order to facilitate sulfur loading and to be advantageous in securing ion diffusion pathways.

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

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

[0087] The porous carbon material is 1,000 m 2 It has a specific surface area of ​​1 / g or more. Specifically, the BET specific surface area of ​​the porous carbon material is not particularly limited in its upper limit, but 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 It may be less than / g. The sulfur-carbon composite according to one embodiment of the present invention has the advantage of containing a large number of micropores on its outer surface and / or interior, and having 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 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 (77K) using BELSORP-max manufactured by BEL Japan.

[0089] The porous carbon material is 4 cm 3 It has a pore volume of 1 / g or more. Specifically, the pore volume of the porous carbon material is not particularly limited to an upper limit, but 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 Less than / g, or 6.5cm 3 / g or more 7.5cm 3 It may be less than or equal to / g. The pore volume may be a value calculated and measured, for example, through N2 adsorption isotherm analysis 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 sulfur-containing compounds.

[0091] In one embodiment of the present invention, the porous carbon material contains a large number of micropores on its outer surface and interior, wherein the micropores include mesopores with a diameter of 1 nm or more and less than 50 nm, and macropores with a diameter of 50 nm or more and 200 nm or less. In one embodiment of the present invention, it is preferable that the mesopores and macropores are uniformly distributed in the porous carbon material.

[0092] The diameter of the micropores can be measured by known methods in the industry for measuring the diameter of pores in porous materials, and there are no particular limitations on the measurement method. For example, the average diameter of the micropores may be measured by scanning electron microscopy (SEM), field emission electron microscopy, or laser diffraction. For measurements using laser diffraction, a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT3000) can be used.

[0093] In other embodiments of the present invention, the average diameter (D50) of the overall pores in the porous carbon material may be, for example, 20 nm to 25 nm, but is not limited thereto. The average diameter (D50) refers to the diameter at the 50% point of the cumulative distribution of pores according to their diameter.

[0094] In the present invention, a sulfur compound is contained in at least a portion of the outer surface and the interior of the pores of the porous carbon material having the above-described properties.

[0095] The sulfur compound can be used without limitation as long as it is suitable for use as a positive electrode active material in lithium-sulfur secondary batteries. For example, the sulfur compound may be inorganic sulfur (S8), lithium polysulfide (Li2S n , 1≦n≦8), carbon sulfur polymer ((C2S x ) m This may include, but is not limited to, 2.5 ≤ x ≤ 50, 2 ≤ m, or mixtures thereof.

[0096] The sulfur compound may be included in the sulfur-carbon composite by physical adsorption with the porous carbon material, or by chemical bonding such as covalent bonding or van der Waals bonding between the sulfur element and carbon within 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 in a weight ratio of 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 and 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 and is advantageous in terms of improving conductivity due to the porous carbon material, but the present invention is not limited thereto.

[0098] In other embodiments of the present invention, the content of the sulfur compound in the sulfur-carbon composite may be, for example, 10% by weight or more, specifically 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 85% by weight or more, based on the total weight of the sulfur-carbon composite. Alternatively, within the above range, it may be 50% by weight to 90% by weight, specifically 60% by weight to 90% by weight, 70% by weight to 90% by weight, or 85% by weight to 90% by weight, 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 range, the high content of the sulfur compound enhances the dynamic activity of the sulfur-carbon composite and is also advantageous in terms of improving conductivity due to 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 by scanning electron microscopy (SEM), field emission electron microscopy, or laser diffraction. For measurement using laser diffraction, for example, a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT3000) may be used. The average particle size (D50) refers to the particle size at the 50% point of the cumulative number distribution according to the 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) may be 1 or less. For example, the above I G / I D If the ratio exceeds 1, there may be problems such as increased crystallinity on the surface of the sulfur-carbon composite, which reduces the efficiency of compounding with sulfur-containing compounds or the conversion reaction of lithium polysulfide.

[0101] The aforementioned Raman peak intensity ratio is obtained from the spectrum of the carbon composite obtained by Raman spectroscopy. G and I D It can be measured through the value. In the resulting spectrum, I G This refers to the peak of the crystalline portion (G-peak, 1573 / cm), and I D This represents the peak in the amorphous region (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 can be formed by mixing the porous carbon material and the sulfur compound and then heat-treating it, but the manufacturing method of the present invention is not limited thereto.

[0103] The sulfur-carbon composite of the present invention, as described above, includes a plate-like carbon material having a large specific surface area and pore volume, which not only increases the amount of sulfur supported but also provides numerous active sites for sulfur oxidation / reduction reactions. As a result, when used in the positive electrode of a lithium-sulfur battery, it can improve battery efficiency and energy density, but 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 described above. 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, The process involves injecting the aforementioned block copolymer into a solution in which porous carbon material is dispersed, thereby coating the block copolymer onto at least one surface of the porous carbon material. The steps include crosslinking the block copolymer coated on the porous carbon material to form a crosslinked block copolymer, A method for producing a sulfur-carbon composite is provided, comprising the step of supporting sulfur on a porous carbon material coated with the aforementioned crosslinked block copolymer.

[0106] In one embodiment of the present invention, the porous carbon material (e.g., Ketjenblack (KB)) and chloride (e.g., FeCl3) can be dispersed in a solvent. For example, the solvent is not particularly limited as long as it is a solvent capable of dissolving or dispersing the compound, and includes 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 acetate cellosolve; ethylene glycol, ethyl acetate These solvents may include polyhydric alcohols and their derivatives such as ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, dimethoxyethane, propylene glycol, diethoxymethane, triethylene glycol monoethyl ether, glycerin, and 1,2-hexanediol; alcoholic solvents such as methanol, ethanol, propanol, isopropanol, and cyclohexanol; sulfoxide solvents such as dimethyl sulfoxide; and amide solvents such as N-methyl-2-pyrrolidone and N,N-dimethylformamide; benzoate solvents such as butyl benzoate and methyl-2-methoxybenzoate; tetralin; and 3-phenoxytoluene.

[0107] Next, the block copolymer described above can be injected into the solution in which the porous carbon material is dispersed, 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] Subsequently, the block copolymer can be crosslinked in the porous carbon material by injecting a crosslinking agent (for example, a dihalogenated alkane compound such as diiodobutane) into a solution in which the porous carbon material coated with the block copolymer is dispersed, and then heat-treating it at approximately 45°C for 24 hours.

[0109] Subsequently, the sulfur-carbon composite can be produced by supporting a sulfur compound on the porous carbon material coated with the crosslinked block copolymer and then heat-treating it. 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] When the cross-linked block copolymer is coated onto the porous carbon material, lithium polysulfide leached from the positive electrode of the lithium-sulfur battery is prevented from being transferred to the negative electrode. Therefore, the accumulation of sulfur particles on the surface of the lithium metal of the negative electrode is prevented, thereby maintaining the charge and discharge capacity of the lithium-sulfur battery and improving its battery life.

[0111] The present invention will be described in detail below with reference to examples to aid in understanding the present invention. However, the examples of 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 give a more complete explanation of the present invention to a person of average knowledge in the industry.

[0112] <Example 1> Manufacturing of block copolymers 1) Preparation of the first monomer: PEGMA-PBA (hereinafter referred to as PP) was synthesized by reacting 1-pyrene butyric acid (PBA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) in toluene solvent at 110°C under the catalysis of p-toluenesulfonic acid (pTsOH). The synthesized PP was purified by three extractions with H2O / 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 via 1H NMR and are shown in Figure 2.

[0114] 2) Preparation of the second monomer: Dimethylaminoethyl acrylate (DMAEMA), a chain transfer agent (CTA, 4-cyano-4-(((tridecylthio)carbonothio)thio)pentanoic acid), and AIBN were dissolved in dioxane solvent, and oxygen was removed from the solution by freeze-pump-thawing three times. The oxygen-free 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 1H 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)), CTA (4-cyano-4-(((tridecylthio)carbonothio)thio)pentanoic acid), and AIBN prepared as described above were dissolved in dioxane solvent, and oxygen in the solution was removed by freeze-pump-thaw three times. The oxygen-free 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 1H NMR and GPC analysis and are shown in Figure 6.

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

[0119] 2) Dissolve PDbPP (10 wt%) relative to KB in chloroform, then add it dropwise to the KB-dispersed solution and stir at room temperature for 24 hours to perform coating.

[0120] 3) CPDbPP10-KB is produced by crosslinking the coated PDbPP by adding diiodobutane dropwise to a solution in which KB coated with PDbPP is dispersed, and then reacting at 45°C for 24 hours.

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

[0122] positive electrode As the positive electrode active material, a sulfur-carbon composite (CPDbPP10-KB-S) was used, which consisted of a Ketjenblack coated with the aforementioned cross-linked block copolymer and supported with a sulfur compound.

[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. The solid content was then adjusted to 18 wt% to produce a cathode slurry. The cathode slurry was then uniformly applied to an aluminum foil to a thickness of 400 μm and dried at 50°C before being used as the cathode. The weight ratio of the crosslinked block copolymer to the cathode was 8.5 wt%.

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

[0125] <Comparative Example 1> positive electrode The cathode was prepared in the same manner as in Example 1, except that a sulfur-carbon composite, a mixture of Ketjenblack and a sulfur compound in a weight ratio of 3:7, was used as the cathode active material.

[0126] Separation membrane, negative electrode, and electrolyte The separation membrane, negative electrode, and electrolyte were prepared in the same manner as in Example 1.

[0127] <Comparative Example 2> positive electrode As the positive electrode active material, a sulfur-carbon composite was used, which was prepared by (1) supporting a sulfur compound on Ketjenblack, (2) coating the Ketjenblack with the sulfur compound with the block copolymer, 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 after adding 0.5 wt% of PVA dispersant, the solid content was adjusted to 18 wt% to produce a positive electrode slurry. The positive electrode slurry was then uniformly applied to an aluminum foil to a thickness of 400 μm and dried at 50°C before being used as the positive electrode. The weight ratio of the crosslinked block copolymer to the positive electrode was 3 wt%.

[0128] Separation membrane, negative electrode, and electrolyte The separation membrane, negative electrode, and electrolyte were prepared in the same manner as in Example 1.

[0129] <Comparative Example 3> positive electrode The cathode was prepared in the same manner as in Comparative Example 2, except that the weight ratio of Ketjenblack coated with the aforementioned cross-linked block copolymer to the sulfur compound was 1:9 (CPDbPP10-KB:S=1:9(w / w)).

[0130] Separation membrane, negative electrode, and electrolyte The separation membrane, negative electrode, and electrolyte were prepared in the same manner as in Example 1.

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

[0132] Separation membrane, negative electrode, and electrolyte The separation membrane, negative electrode, and electrolyte were prepared in the same manner as in Example 1.

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

[0134] Separation membrane, negative electrode, and electrolyte The separation membrane, negative electrode, and electrolyte were prepared in the same manner as in Example 1.

[0135] Figure 7 is a graph showing the evaluation of discharge capacity after charging and discharging under the following conditions at 25°C.

[0136] Evaluation equipment: WBSC3000 battery cycler (manufactured by WonA Tech) Current density: 0.2C rate Referring to Figure 7, the lithium-sulfur battery according to Example 1 showed a higher discharge capacity during the period from 1 to 100 cycles compared to the lithium-sulfur battery according to Comparative Example 1.

[0137] Figure 8 is a graph showing the evaluation of discharge capacity after charging and discharging under the following conditions at 25°C.

[0138] Evaluation equipment: WBSC3000 battery cycler (manufactured by WonA Tech) Current density: 1C rate Referring to Figure 8, the lithium-sulfur battery according to Example 1 showed a higher discharge capacity during the 40 to 160 cycle period compared to the lithium-sulfur battery according to Comparative Example 1.

[0139] Figures 9 and 10 are graphs showing the evaluation of discharge capacity after charging and discharging under the following conditions at 25°C.

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

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

[0142] On the other hand, referring to Figure 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 confirmed in Figure 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 comprising a first repeating unit having a pyrene group at its terminus, A block copolymer comprising a second block containing a second repeating unit having a cationic functional group.

2. The block copolymer according to claim 1, wherein the molar ratio of the first block to the second block is 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 a pyrene group at its terminus and an alcohol compound having a (meth)acrylate group.

4. The first repeating unit is given by the following chemical formula 1: 【Chemistry 1】 It is represented as, In chemical formula 1, R １ R is a linker group, an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an allylene group having 6 to 20 carbon atoms. ２ The block copolymer according to claim 1, wherein is hydrogen, a C1-C10 alkyl group, a C3-C10 cycloalkyl group, or a C6-C20 aryl group, and n is 0 to 1,000,000.

5. The second repeating unit is given by the following chemical formula 2: 【Chemistry 2】 Includes, 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, and R ５ is -NR ６ R ７ where R ６ and R ７ are each independently 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, the block copolymer according to Claim 1.

6. The first repeating unit is shown in chemical formula 3 below: 【Transformation 3】 It is represented as follows, and in chemical formula 3, n is between 1 and 1,000,000. The second repeating unit is shown in chemical formula 4 below: 【Chemistry 4】 The block copolymer according to claim 1, which is represented by and in chemical formula 4, m is between 1 and 1,000,000.

7. The present invention comprises a first block copolymer and a second block copolymer having the same structure as the first block copolymer and being crosslinked with the first block copolymer. The crosslinked block copolymer wherein the first block copolymer is the block copolymer according to any one of claims 1 to 6.

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

9. Porous carbon material, A coating layer located on at least one surface of the porous carbon material, comprising the crosslinked block copolymer described in claim 7, A sulfur-carbon composite comprising a sulfur compound located on the surface of the porous carbon material, within the pores of the porous carbon material, and on at least a portion of the surface of the coating layer.

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

15.

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

6.

12. It includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, The lithium-sulfur battery wherein the positive electrode contains the sulfur-carbon composite described in claim 9.

13. A step of injecting a 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 onto at least one surface of the porous carbon material; The steps include crosslinking the block copolymer coated on the porous carbon material to form a crosslinked block copolymer, A method for producing a sulfur-carbon composite, comprising the step of supporting a sulfur compound on a porous carbon material coated with the aforementioned crosslinked block copolymer.

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 and heat-treating it.

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

Images