Binder composition for secondary battery electrodes, positive electrode for lithium-sulfur secondary battery containing the same, and lithium-sulfur secondary battery

Abstract

The present invention provides a binder composition for secondary battery electrodes, a positive electrode for a lithium-sulfur secondary battery, and a lithium-sulfur secondary battery, which contain lithium-substituted polyacrylic acid, lithium-substituted carboxymethyl cellulose, and a colloidal particulate aqueous binder resin, thereby maintaining high levels of productivity and output performance and improving adhesive strength in the electrode.

Description

[Technical Field]

[0001] The present invention relates to a binder composition for a secondary battery electrode, a positive electrode for a lithium-sulfur secondary battery containing the same, and a lithium-sulfur secondary battery.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0183530, filed on December 23, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings of that application. [Background technology]

[0003] As the range of applications for lithium secondary batteries expands beyond portable electronic devices to include electric vehicles (EVs) and energy storage systems (ESS), the demand for high-capacity, high-energy density, and long-life lithium secondary batteries is increasing.

[0004] Among the various lithium secondary batteries, lithium-sulfur batteries are a battery system that uses sulfur compounds containing sulfur-sulfur (SS) bonds as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the main material used for the positive electrode active material, has a low atomic weight and is abundant in resources, making it easy to supply and demand, inexpensive, non-toxic, and environmentally friendly. Furthermore, lithium-sulfur batteries have attracted the most attention among the secondary batteries developed to date because they exhibit higher capacity than other battery systems.

[0005] The sulfur used in lithium-sulfur batteries has an electrical conductivity of approximately 5 x 10 -30 Since sulfur-containing materials are non-conductive with a conductivity of S / cm, it is difficult for electrons generated by electrochemical reactions to move. Therefore, sulfur-containing materials are combined with conductive materials such as carbon, which can provide chemical reaction sites, to form sulfur-carbon composites, which are then used as cathode active materials.

[0006] On the other hand, in lithium-sulfur batteries, when the battery is discharged, lithium, the negative electrode active material, gives up electrons and is ionized into lithium cations, while the sulfur-based material, the positive electrode active material, receives electrons and is reduced. Here, the S-S bond receives two electrons through the reduction reaction of the sulfur-based material, changing into the form of a sulfur anion. The lithium cations generated by the oxidation reaction of lithium are transferred to the positive electrode via the electrolyte, where they combine with sulfur anions generated through the reduction reaction of the sulfur-based compound to form a salt. Specifically, sulfur before discharge has a cyclic S8 structure, which is reduced to lithium polysulfide (Li2S) through the reduction reaction. x , x=8,6,4,2), which is then completely reduced to form lithium sulfide (Li2S). However, lithium polysulfides generated during the charge and discharge process are prone to leaching into the electrolyte, causing a decrease in battery capacity and cell degradation. To solve the problem of lithium polysulfide leaching, sulfur is supported in the pores of various porous carbon materials and used in the positive electrode.

[0007] However, sulfur-carbon composites containing porous carbon materials require a binder with high adhesive strength to be used in cathodes due to their low density and large surface area. Although various binders have been investigated, it has been difficult to simultaneously improve productivity, power output, and adhesive strength. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a binder composition for secondary battery electrodes that can maintain high levels of productivity and output performance and improve adhesive strength in electrodes, as well as a positive electrode for a lithium-sulfur secondary battery and a lithium-sulfur secondary battery that include the same.

[0009] The objects and advantages of the present invention can be realized by the means, methods, and combinations set forth in the claims. [Means for solving the problem]

[0010] The present inventors have found that the above-mentioned problems can be solved by the following binder composition for secondary battery electrodes, and a positive electrode for a lithium-sulfur secondary battery and a lithium-sulfur secondary battery containing the same.

[0011] According to the first embodiment, The binder resin includes a first binder resin, a second binder resin, and a third binder resin, the first binder resin is a lithium-substituted polyacrylic acid; the second binder resin is lithium-substituted carboxymethyl cellulose; The third binder resin relates to a binder composition for a secondary battery electrode, which is a colloidal particulate water-based binder resin.

[0012] According to the second embodiment, in the first embodiment, The first binder resin relates to a binder composition for a secondary battery electrode, wherein the first binder resin contains at least one type of lithium-substituted polyacrylic acid, and the lithium-substituted polyacrylic acid has a weight-average molecular weight MW of 300,000 to 1,500,000.

[0013] According to the third embodiment, in the first or second embodiment, The first binder resin relates to a binder composition for a secondary battery electrode, which comprises at least two kinds of lithium-substituted polyacrylic acids having different molecular weights.

[0014] According to a fourth embodiment, in any one of the first to third embodiments, The present invention relates to a binder composition for secondary battery electrodes, wherein the viscosity of a 1.0% aqueous solution of the second binder resin is 100 to 10,000 cP.

[0015] According to the fifth embodiment, in any one of the first to fourth embodiments, The third binder resin relates to a binder composition for a secondary battery electrode, which is a styrene-butadiene rubber, an acrylic polymer containing repeating units derived from at least one acrylic monomer, or a mixture of two or more of these.

[0016] According to the sixth embodiment, in any one of the first to fifth embodiments, The present invention relates to a binder composition for a secondary battery electrode, wherein the pH of a 1.0 to 10.0% aqueous solution of the first binder resin and the second binder resin each falls within the range of 6 to 9.

[0017] According to the seventh embodiment, in any one of the first to sixth embodiments, The present invention relates to a binder composition for a secondary battery electrode, which further contains an aqueous binder resin as a fourth binder resin.

[0018] According to the eighth embodiment, in any one of the first to seventh embodiments, Based on a total of 100% by weight of the binder composition, the first binder resin comprises 5 to 80% by weight, the second binder resin is contained in an amount of 5 to 80% by weight, The present invention relates to a binder composition for a secondary battery electrode, which contains 5 to 80% by weight of the third binder resin.

[0019] According to the ninth embodiment, in any one of the first to eighth embodiments, The present invention relates to a binder composition for a secondary battery electrode, in which the first binder resin and the second binder resin are contained in an amount of 20 to 60% by weight based on 100% by weight of the total of the binder composition.

[0020] According to the tenth embodiment, in any one of the first to ninth embodiments, The third binder resin is contained in an amount of 30 to 75% by weight based on 100% by weight of the total binder composition, and relates to a binder composition for a secondary battery electrode.

[0021] According to the eleventh embodiment, in any one of the first to tenth embodiments, Based on a total of 100% by weight of the binder composition, the first binder resin is contained in an amount of 5 to 50% by weight, the second binder resin is contained in an amount of 5 to 40% by weight, The present invention relates to a binder composition for a secondary battery electrode, which contains 30 to 75% by weight of the third binder resin.

[0022] In a twelfth embodiment, a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material and a binder resin, The binder resin relates to a positive electrode for a lithium-sulfur secondary battery, including the binder composition for a secondary battery electrode according to any one of the first to eleventh embodiments.

[0023] In a thirteenth embodiment, A twelfth embodiment relates to a lithium-sulfur secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. [Effects of the Invention]

[0024] The present invention provides a novel binder composition for secondary battery electrodes, which includes lithium-substituted polyacrylic acid, lithium-substituted carboxymethyl cellulose, and a colloidal particulate aqueous binder resin, thereby maintaining high productivity and output performance and exhibiting excellent adhesive strength.

[0025] 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, so the present invention should not be interpreted as being limited to the matters depicted in the drawings. Note that the shape, size, scale, or ratio of elements in the drawings attached to this specification may be exaggerated to emphasize a clearer description. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a graph showing the results of measuring adhesive strength in examples of the present invention and comparative examples. [Figure 2] 1 is a graph showing measurement results of power density in an example of the present invention and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical concept of the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best explain the invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical concept of the present invention, and therefore, various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0028] Throughout this specification, when a part "includes" or "comprises" certain elements, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0029] As used throughout this specification, the terms "about," "substantially," and the like are used to mean a numerical value or a approximation thereof when inherent manufacturing and material tolerances are present in the stated meaning, and are used to prevent unscrupulous infringers from unfairly using disclosures in which precise or absolute numerical values ​​are recited to aid in the understanding of this application.

[0030] Throughout this specification, the phrase "A and / or B" means "A or B, or all of them."

[0031] Throughout this specification, unless otherwise specified, temperature units refer to degrees Celsius and are expressed in "°C".

[0032] The present invention relates to a binder composition for a secondary battery electrode, a positive electrode for a lithium-sulfur secondary battery containing the same, and a lithium-sulfur secondary battery.

[0033] Binder composition for electrodes In one embodiment of the present invention, an electrode binder composition includes a first binder resin, a second binder resin, and a third binder resin, wherein the first binder resin is lithium-substituted polyacrylic acid, the second binder resin is lithium-substituted carboxymethyl cellulose, and the third binder resin is a colloidal particulate aqueous binder resin. The present invention provides an electrode binder composition that maintains high productivity and output performance and exhibits excellent adhesive strength by including a specific combination of a first binder resin that contributes to improved processability and a third binder resin that contributes to improved adhesive strength together with the second binder resin. Furthermore, optimal battery output and high adhesive strength can be simultaneously achieved by adjusting the blend ratio of the first binder resin, which is favorable for output, and the second binder resin, which has interfacial properties that enable efficient adhesion of the third binder resin. The electrode binder composition according to the present invention can be used for both anodes and / or cathodes. In particular, as long as an aqueous solvent can be used in the production of the electrode, the type of electrode is not limited.

[0034] The first binder resin is a lithium-substituted polyacrylic acid.

[0035] The lithium-substituted polyacrylic acid is a form in which hydrogen atoms in the carboxyl group (COOH) of polyacrylic acid are substituted with lithium atoms. The lithium-substituted polyacrylic acid can be formed by neutralizing polyacrylic acid by adding a lithium-containing base to polyacrylic acid. The lithium-substituted polyacrylic acid is preferably formed by adding a base so that the molar ratio of the carboxyl group of polyacrylic acid to lithium is 1:1, and then completely neutralizing the polyacrylic acid. For example, the lithium-substituted polyacrylic acid of the present invention can be formed by neutralizing the polyacrylic acid using LiOH to a pH range of 6 to 9 or 6.5 to 8. If the polyacrylic acid is not completely neutralized, side reactions may occur due to hydrogen generated from the polyacrylic acid. Furthermore, if an excessive amount of base is added, the base that does not participate in the neutralization reaction may deteriorate the battery life characteristics. The lithium substitution increases the polarity of polyacrylic acid, improving its dispersibility in a solvent. The lithium-substituted polyacrylic acid not only serves as a binder that enhances the adhesive strength between electrode active materials and / or between the electrode active material and the electrode current collector, but also suppresses by-products generated during battery operation, thereby improving the stability of the electrode.

[0036] In the present invention, "pH" can be measured by a pH titration method or a potentiometric pH meter commonly used in the technical field to which the present invention pertains. Specifically, it can be measured using a pH measuring device comprising a glass electrode, for example, a Mettler Toledo SevenExcellence pH meter. When the sample is in a solid form rather than an aqueous solution, 0.5 g to 20 g of the solid sample can be added to 100 g of distilled water, stirred for 10 minutes, and then measured at room temperature (25°C).

[0037] According to an embodiment of the present invention, the first binder resin includes at least one lithium-substituted polyacrylic acid, and the lithium-substituted polyacrylic acid may have a weight-average molecular weight Mw of 300,000 to 1,500,000. By including a lithium-substituted polyacrylic acid having a weight-average molecular weight in this range, electrode adhesion strength and productivity can be improved.

[0038] When at least two kinds of lithium-substituted polyacrylic acids are included, the molecular weights of the lithium-substituted polyacrylic acids are different from each other. Specifically, the lithium-substituted polyacrylic acids may be at least one kind, at least two kinds, or at least three kinds.

[0039] When at least two types of lithium-substituted polyacrylic acids are included, the lithium-substituted polyacrylic acid with a relatively high molecular weight can contribute to increasing the adhesive strength of the binder and improving the life stability of the battery, while the lithium-substituted polyacrylic acid with a relatively low molecular weight can contribute to improving the processability of the binder by increasing the solid content during slurry preparation and increasing the fluidity of the slurry. Therefore, the present invention may be configured so that the at least two types of lithium-substituted polyacrylic acids include one lithium-substituted polyacrylic acid with a relatively high molecular weight and one lithium-substituted polyacrylic acid with a relatively low molecular weight.

[0040] In this specification, the weight average molecular weight (Mw) is determined by converting the value measured by GPC (Gel Permeation Chromatography) to standard polystyrene, and specifically, it can be determined by gel permeation chromatography (GPC) as described in ASTM method D5296. For example, the following GPC measurement conditions can be proposed.

[0041] GPC measurement device: ACQUITY APC (Waters) Column: PL gel Mixed-B + C (Agilent) Column temperature: RT (20-25°C) Eluent: DMF / 0.05M LiBr Flow rate: 1.0ml / min Detector: Waters 2414 RI detector Sample concentration: ~1mg / ml (0.45μm syringe filter) Injection volume: 10μl Calibration curve: Polystyrene

[0042] The second binder resin is lithium-substituted carboxymethyl cellulose.

[0043] The lithium-substituted carboxymethyl cellulose can provide excellent adhesion to the surface of not only the electrode active material but also the electrode current collector. It also functions as a dispersant in the binder composition, particularly when mixed with the positive electrode active material, to improve the dispersibility of the positive electrode active material. Furthermore, its high viscosity can improve the stability of the slurry.

[0044] The lithium-substituted carboxymethyl cellulose may be formed by adding a lithium-containing base to carboxymethyl cellulose through a neutralization reaction, followed by linearization, or by directly binding lithium ions to carboxymethyl cellulose. For example, when formed by a neutralization reaction, the lithium-substituted carboxymethyl cellulose is preferably formed by adding a base so that the molar ratio of carboxymethyl cellulose to lithium is 1:1, and then completely neutralizing the carboxymethyl cellulose. For example, the lithium-substituted carboxymethyl cellulose of the present invention may be formed by neutralizing the carboxymethyl cellulose to a pH range of 6 to 9 or 6.5 to 8 using LiOH. If the carboxymethyl cellulose is not completely neutralized, the remaining H in the carboxymethyl cellulose may be dissolved in water. + , Na + Li by ions etc. + The ionic conductivity or reversibility of the lithium anode may decrease, resulting in a decrease in battery performance. In addition, if an excessive amount of base is added, the battery life characteristics may be deteriorated due to the base not participating in the neutralization reaction. Due to the aforementioned lithium substitution, carboxymethyl cellulose is +By increasing ionic conductivity and removing other cations, it is possible to prevent the resulting deterioration of battery performance. The lithium-substituted carboxymethyl cellulose not only acts as a binder to enhance adhesion between electrode active materials and / or between the electrode active material and the electrode current collector, but also suppresses side reaction products generated during battery operation, thereby improving electrode stability. Furthermore, compared to non-lithiated carboxymethyl cellulose, lithium-substituted carboxymethyl cellulose exhibits a prelithiation effect, which can replenish lithium consumed in the electrode during battery operation, thereby increasing initial efficiency and improving battery performance.

[0045] In the present invention, "pH" can be measured by a pH titration method or a potentiometric pH meter commonly used in the technical field to which the present invention pertains. Specifically, it can be measured using a pH measuring device with a glass electrode, such as a Mettler Toleo SevenExellence pH meter. When the sample is in a solid form rather than an aqueous solution, 0.5 g to 20 g of the solid sample can be added to 100 g of distilled water, stirred for 10 minutes, and then measured at room temperature (25°C).

[0046] The viscosity of the second binder resin may be 100 to 10,000 cP. Specifically, the viscosity of a 1.0% aqueous solution of the second binder resin may be within this range. By including lithium-substituted carboxymethyl cellulose having a viscosity within this range, the desired adhesive strength and dispersibility can be ensured. When a second binder resin with a low viscosity within this range is used, better dispersibility can be ensured, and when a second binder resin with a high viscosity within this range is used, better adhesive strength can be obtained.

[0047] In this specification, the term "viscosity" refers to a value measured at a predetermined temperature (25°C) using a viscometer commonly used to measure the viscosity of a fluid, such as a Brookfield viscometer (VISCOMETER, TOKIMEC) or a rheometer (Rheometer, TA Instruments). For example, in this specification, the viscosity can be measured desirably at 25°C and a shear rate of 12 rpm using a Brookfield viscometer.

[0048] The third binder resin is a colloidal particulate water-based binder resin.

[0049] The colloidal particulate aqueous binder resin exists in a particulate form that is not dissolved in the aqueous binder composition, thereby suppressing an increase in viscosity of the dissolved polymer and binder composition, and serving as a binder that enhances the adhesive strength between electrode active materials and / or between the electrode active material and the electrode current collector.

[0050] The colloidal particulate aqueous binder resin is present in a dispersed state in an aqueous solvent, and is stably dispersed in the form of particles that are not dissolved but are nearly spherical and have an average particle size D50 of 50 to 500 nm. The average particle size D50 may refer to the particle size at the 50% point of the cumulative particle number distribution by particle size.

[0051] The colloidal particulate water-based binder resin may be a styrene-butadiene rubber, an acrylic polymer containing repeating units derived from at least one acrylic monomer, or a mixture of two or more thereof.

[0052] The acrylic polymer may be any polymer containing repeating units derived from at least one acrylic monomer, for example, an acrylic polymer containing repeating units derived from one acrylic monomer or a copolymer containing repeating units derived from at least two or more acrylic monomers.

[0053] The acrylic monomer may be acrylic acid, alkyl acrylate, alkyl methacrylate, isoalkyl(meth)acrylate, etc., where "alkyl" is an alkyl group having 1 to 10 carbon atoms, more specifically, an alkyl group having 1 to 5 carbon atoms. Specific examples include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, pentyl(meth)acrylate, etc. Preferably, the acrylic monomer may be an acrylic copolymer containing repeating units derived from acrylic acid and butyl(meth)acrylate.

[0054] According to a specific embodiment of the present invention, in the binder composition for an electrode, the contents of the first binder resin, the second binder resin, and the third binder resin may be within the following ranges.

[0055] Specifically, the first binder resin may be included in an amount of 5 to 80 wt %, more specifically 5 to 50 wt %, or 12.5 to 45 wt %, based on a total of 100 wt % of the electrode binder composition. When the content of the first binder resin is included in the above range, sedimentation of the positive electrode active material can be suppressed, and an increase in battery resistance due to the addition of an excessive amount of binder can be prevented.

[0056] The second binder resin may be included in an amount of 5 to 80 wt %, specifically 5 to 40 wt %, or 5 to 37.5 wt %, based on the total weight of the electrode binder composition (100 wt %). When the content of the second binder resin is within the above range, excellent adhesion between the positive electrode active materials and / or between the positive electrode active material and the positive electrode current collector can be provided, and an increase in battery resistance due to the addition of an excessive amount of binder can be prevented.

[0057] The third binder resin may be included in an amount of 5 to 80 wt %, specifically 30 to 75 wt % or 40 to 65 wt %, based on a total of 100 wt % of the electrode binder composition. When the content of the third binder resin is included in the above range, sedimentation of the positive electrode active material can be suppressed, excellent adhesion between the positive electrode active materials and / or between the positive electrode active material and the positive electrode current collector can be provided, and an increase in battery resistance due to the addition of an excessive binder can be prevented.

[0058] In addition, the first binder resin and the second binder resin may be included in an amount of 20 to 60 wt % or 40 to 60 wt % based on a total of 100 wt % of the electrode binder composition. When the sum of the contents of the first binder resin and the second binder resin is within the above-mentioned range, sedimentation of the positive electrode active material can be suppressed, excellent adhesion between the positive electrode active materials and / or between the positive electrode active material and the positive electrode current collector can be provided, and an increase in battery resistance due to the addition of an excessive amount of binder can be prevented.

[0059] When the first binder resin, the second binder resin, and the third binder resin all satisfy the content ranges provided, not only can the electrode exhibit improved adhesive strength, but also the battery performance can be improved. In addition, a positive electrode having an appropriate weight that is not excessive can be produced, thereby providing a balanced cell energy density and being advantageous in terms of battery capacity.

[0060] According to a specific embodiment of the present invention, the binder composition for an electrode of the present invention may further include a water-based binder resin as a fourth binder resin.

[0061] The fourth binder resin is different from the first binder resin, the second binder resin, and the third binder resin, and may include, for example, carboxymethyl cellulose (CMC), hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyethylene glycol, polyacrylonitrile, polyacrylamide, polyvinyl alcohol, polyethylene oxide, or a mixture or copolymer of two or more thereof.

[0062] <Positive electrode for lithium-sulfur batteries> In one embodiment of the present invention, the positive electrode for a lithium-sulfur battery comprises: a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector, The positive electrode active material layer includes a positive electrode active material and a binder resin.

[0063] The positive electrode active material may be contained in an amount of 50 to 99% by weight, or 90 to 99% by weight, relative to 100% by weight of the positive electrode active material layer.

[0064] The binder resin may include the above-described binder composition for an electrode. Specifically, the binder resin may be the above-described binder composition for an electrode. The binder resin may be included in an amount of 0.5 to 10 wt % or 1 to 5 wt % relative to 100 wt % of the positive electrode active material layer.

[0065] The positive electrode current collector is used to support the positive electrode active material and is not particularly limited as long as it has high conductivity and does not induce chemical changes in the battery. The positive electrode current collector can typically be formed to a thickness of 3 to 500 μm and can be made of conductive materials such as stainless steel, aluminum, copper, or titanium. When a carbon-coated aluminum substrate is used, it has the advantages of excellent adhesion to the positive electrode active material, low contact resistance, and prevention of corrosion by aluminum polysulfides. The positive electrode current collector can also be in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0066] The positive electrode active material may include at least one sulfur-based material selected from the group consisting of elemental sulfur (S8) and sulfur compounds. Examples of the sulfur-based material include inorganic sulfur (S8), Li2S, and the like. n (n≧1), disulfide compounds such as 2,5-dimercapto-1,3,4-thiadiazole, 1,3,5-trithiocyanuic acid, etc., organic sulfur compounds, and carbon-sulfur polymers (C2S x ) n , x=2.5 to 50, n≧2). Preferably, the positive electrode active material may contain inorganic sulfur (S8).

[0067] Since sulfur contained in the positive electrode active material does not have electrical conductivity by itself, it is used together with a conductive material such as a carbon material. Therefore, the positive electrode active material may be a sulfur-carbon composite, and the sulfur-carbon composite may include a sulfur-based material.

[0068] The carbon contained in the sulfur-carbon composite is a porous carbon material that provides a framework for uniformly and stably immobilizing sulfur and compensates for the low electrical conductivity of sulfur, facilitating electrochemical reactions.

[0069] The porous carbon material can be prepared by carbonizing various carbonaceous precursors. The porous carbon material contains non-uniform pores, with an average pore diameter ranging from 1 to 200 nm and a porosity ranging from 10 to 90% of the total volume of the porous carbon material. If the average pore diameter is smaller than this range, the pore size is merely at the molecular level, making sulfur impregnation impossible. Conversely, if the average pore diameter exceeds this range, the mechanical strength of the porous carbon material is weakened, making it unsuitable for use in electrode manufacturing processes.

[0070] The shape of the porous carbon material is not particularly limited as long as it is spherical, rod-like, needle-like, plate-like, tubular or bulk-like and can be generally used in lithium-sulfur batteries.

[0071] The porous carbon material has a porous structure or a high specific surface area and may be one commonly used in the art. For example, the porous carbon material may be graphite; graphene; carbon black such as denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs); carbon fibers such as graphite nanofibers (GNFs), carbon nanofibers (CNFs), or activated carbon fibers (ACFs); graphite such as natural graphite, artificial graphite, or expanded graphite; activated carbon, etc.

[0072] The sulfur-carbon composite may contain 60 to 90 wt %, preferably 65 to 85 wt %, more preferably 70 to 80 wt % of a sulfur-based material relative to 100 wt % of the sulfur-carbon composite.

[0073] If the content of the yellow-based material is lower than the above range, the content of the porous carbon material in the sulfur-carbon composite increases relatively, thereby increasing its specific surface area, and therefore the amount of binder used in the cathode production increases relative to the content of sulfur. This increase in binder usage results in increased surface resistance of the cathode and reduces battery performance by acting as an insulator that blocks the passage of electrons. Conversely, if the content of the yellow-based material exceeds the above range, sulfur that cannot bond with the porous carbon material aggregates or re-leaches to the surface of the porous carbon material, making it difficult to accept electrons and unable to participate in the electrochemical reaction, resulting in a decrease in battery capacity.

[0074] In addition, in the sulfur-carbon composite, sulfur is located on at least one of the inner and outer surfaces of the porous carbon material. In this case, sulfur may be present in an area of ​​less than 100%, preferably 1 to 95%, and more preferably 60 to 90% of the entire interior and outer surface area of ​​the porous carbon material. When sulfur is present on the inner and outer surfaces of the porous carbon material within this range, it can maximize the electron transfer area and wettability with the electrolyte. Specifically, within this range, sulfur is impregnated thinly and uniformly on the inner and outer surfaces of the porous carbon material, thereby increasing the electron transfer contact area during charge and discharge. When sulfur is located on 100% of the entire inner and outer surfaces of the porous carbon material, the carbon material is completely covered with sulfur, resulting in poor wettability with the electrolyte and poor contact with the included electrically conductive material, preventing it from receiving electrons at the electrode and participating in the electrochemical reaction.

[0075] The method for preparing the sulfur-carbon composite is not particularly limited in the present invention, and may be a method commonly used in the art. For example, a method may be used in which sulfur and a porous carbon material are simply mixed together and then heat-treated to form a composite.

[0076] In addition to the above, the positive electrode active material may further include one or more additives selected from a transition metal element, a Group IIIA element, a Group IVA element, sulfur compounds of these elements, and alloys of these elements with sulfur, as well as the above-mentioned components.

[0077] Examples of the transition metal elements include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au, and Hg. Examples of the IIIA group elements include Al, Ga, In, and Tl. Examples of the IVA group elements include Ge, Sn, and Pb.

[0078] The sulfur may be contained in an amount of 40 to 95 wt %, preferably 50 to 90 wt %, and more preferably 60 to 85 wt %, based on 100 wt % of the positive electrode active material layer constituting the positive electrode active material layer. In one embodiment of the present invention, when a sulfur-carbon composite is used as the positive electrode active material, the sulfur-carbon composite may be contained in an amount of 90 to 97 wt %, based on 100 wt % of the positive electrode active material layer. If the content of the positive electrode active material is less than the above range, the electrochemical reaction of the positive electrode is difficult to sufficiently exhibit. Conversely, if the content exceeds the above range, the content of the conductive material and binder (described later) becomes relatively insufficient, resulting in increased positive electrode resistance and reduced physical properties of the positive electrode.

[0079] The positive electrode for the lithium-sulfur battery may be prepared by coating a positive electrode current collector with a positive electrode slurry containing the positive electrode active material and the binder resin.

[0080] In one embodiment of the present invention, the positive electrode slurry may have a solid content concentration of 20 wt % to 50 wt %. In the present invention, the solid content refers to the solid components in the slurry excluding the solvent and the like.

[0081] The positive electrode slurry may further contain additives, which are substances commonly used to improve the performance of the positive electrode slurry, as needed. Since common additives can be used, a description of the additives will be omitted in this specification.

[0082] In the present invention, the method for applying the positive electrode slurry is not particularly limited. For example, a doctor blade method, a die casting method, a comma coating method, a screen printing method, etc. may be used. Alternatively, after forming a separate substrate, the positive electrode slurry may be applied onto the positive electrode current collector by pressing or laminating.

[0083] After the coating, a drying process may be performed to remove the solvent. The drying process is performed at a temperature and time that allows the solvent to be sufficiently removed. The conditions may vary depending on the type of solvent, and are not particularly limited in the present invention. Examples of drying methods include drying using warm air, hot air, or low-humidity air, vacuum drying, and drying using (far-infrared) radiation or electron beam irradiation. The drying rate may be adjusted so that the solvent is removed as quickly as possible within a range that does not cause cracks in the positive electrode active material layer due to stress concentration and does not cause the positive electrode active material layer to peel off from the positive electrode current collector.

[0084] After drying, the current collector can be pressed to increase the density of the positive electrode active material in the positive electrode. Examples of pressing methods include mold pressing and roll pressing.

[0085] Lithium-sulfur battery In one embodiment of the present invention, there is provided a lithium-sulfur battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode includes the above-described positive electrode.

[0086] The negative electrode may be any material that can be commonly used as a negative electrode for a lithium-sulfur battery. Specifically, the negative electrode may be a lithium-based metal and may further include a current collector on one side of the lithium-based metal. The current collector may be a negative electrode current collector.

[0087] The lithium-based metal may be lithium or a lithium alloy, which includes an element capable of being alloyed with lithium, specifically, an alloy of lithium with at least one element selected from the group consisting of Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Zn, Ba, Ra, Ge, and Al.

[0088] The lithium-based metal may be in the form of a sheet or foil, and in some cases, lithium or a lithium alloy may be deposited or coated on a current collector by a dry process, or granular metal or alloy may be deposited or coated by a wet process.

[0089] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. It may be selected from the group consisting of copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium, or silver. The alloy may be an aluminum-cadmium alloy. Other examples include calcined carbon and non-conductive or conductive polymers surface-treated with a conductive material. Typically, a copper thin plate is used as the negative electrode current collector. It may take various forms, such as a film, sheet, foil, net, porous material, foam, or non-woven fabric, with or without a micro-textured surface. The negative electrode current collector has a thickness ranging from 3 to 50 μm. A thickness of less than 3 μm results in poor current collection efficiency, while a thickness exceeding 50 μm results in poor processability during cell folding and assembly.

[0090] In an embodiment of the present invention, the electrolyte may be any electrolyte commonly used in lithium-sulfur batteries, including, but not limited to, an organic solvent and a lithium salt.

[0091] The organic solvent serves as a medium for the migration of ions involved in the electrochemical reaction of the battery. As the organic solvent, any organic solvent commonly used in lithium secondary battery electrolytes may be used without limitation. For example, ethers, esters, amides, linear carbonates, cyclic carbonates, etc. may be used alone or in combination. Among these, ether-based compounds may be used as a representative example.

[0092] The ether-based compound may include acyclic ethers and cyclic ethers.

[0093] For example, the acyclic ether may be at least one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, dimethoxyethane, diethoxyethane, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, and polyethylene glycol methyl ethyl ether.

[0094] For example, the cyclic ethers include 1,3-dioxolane, 4,5-dimethyl-dioxolane, 4,5-diethyl-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-ethoxytetrahydrofuran, 2-methyl-1,3-dioxolane, 2-vinyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-methoxy-1,3-dioxolane, 2-ethyl-2-methyl-1,3-dioxolane, tetrahydropyran, 1,4-dioxane, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, and isosorbide dimethyl ether. The thiophene may be at least one selected from the group consisting of, but not limited to, ether, furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, and 2,5-dimethylthiophene.

[0095] Examples of the ester of the organic solvent include, but are not limited to, any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, and mixtures of two or more thereof.

[0096] Specific examples of the chain carbonate compound include, but are not limited to, any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, or a mixture of two or more thereof.

[0097] Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or mixtures of two or more thereof. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC).

[0098] The lithium salt is a compound capable of providing lithium ions in the electrolyte. Examples of such lithium salts include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3CO2, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiCH3SO3, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiC4BO8, LiCl, LiBr, and LiB 10 Cl 10 , LiI, or LiB(C2O4)2 may be used. In the present invention, in order to increase the utilization potential of sulfur and realize a high-capacity, high-voltage battery, the lithium salt preferably includes Li-TFSI. More preferably, the lithium salt may include LiN(CF3SO2)2 (Li-TFSI) in an amount of 80 wt% or more, 90 wt% or more, or 100% based on 100 wt% of the total lithium salt.

[0099] The concentration of the lithium salt is in the range of 0.1 M to 2.0 M, preferably 0.5 M to 1 M, and more preferably 0.5 to 0.75 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, thereby exhibiting excellent electrolyte performance and allowing effective lithium ion mobility. When the lithium salt concentration is below this range, it is difficult to ensure ionic conductivity suitable for battery operation. When the lithium salt concentration exceeds this range, the viscosity of the electrolyte increases, reducing lithium ion mobility or increasing the decomposition reaction of the lithium salt itself, which can degrade battery performance.

[0100] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving battery life characteristics, suppressing battery capacity loss, and improving battery discharge capacity. For example, additives may include nitric acid compounds, nitrous acid compounds, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, which may be used alone or in combination. The additives may be present in an amount of 0.1 wt % to 10 wt %, preferably 0.1 wt % to 5 wt %, based on the total weight of the electrolyte.

[0101] In a specific embodiment of the present invention, the electrolyte may include a nitrate compound and / or a nitrite compound as an additive, which forms a stable coating on the lithium metal electrode as the negative electrode, thereby improving charge / discharge efficiency. Examples of such nitric acid or nitrite compounds include, but are not limited to, inorganic nitric acid or nitrite compounds such as lithium nitrate (LiNO), potassium nitrate (KNO), cesium nitrate (CsNO), barium nitrate (Ba(NO)), ammonium nitrate (NHNO), lithium nitrite (LiNO), potassium nitrite (KNO), cesium nitrite (CsNO), and ammonium nitrite (NHNO); organic nitric acid or nitrite compounds such as methyl nitrate, dialkylimidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrate, propyl nitrate, butyl nitrate, pentyl nitrate, and octyl nitrate; and organic nitro compounds such as nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitropyridine, dinitropyridine, nitrotoluene, and dinitrotoluene, and combinations thereof. In a preferred embodiment of the present invention, the additive may include lithium nitrate.

[0102] In one embodiment of the present invention, the separator is disposed in the electrode assembly between the anode and the cathode. The separator separates the anode and the cathode and provides a path for lithium ions to move. Any separator commonly used in lithium-sulfur batteries may be used without limitation. Specifically, the separator may include a porous polyolefin substrate, and may further include inorganic particles and / or a binder for binding the inorganic particles on at least one surface of the porous polyolefin substrate, as needed.

[0103] The separator may be a film-like electrolyte membrane containing a solid electrolyte, and may further contain a binder to bind the solid electrolyte, if necessary. The solid electrolyte may be any solid electrolyte that can be commonly used in lithium-sulfur batteries, such as a polymer solid electrolyte, an inorganic solid electrolyte, or a mixture thereof, without limitation.

[0104] In one embodiment of the present invention, the shape of the lithium-sulfur battery is not particularly limited, and may be, for example, a coin shape, a cylindrical shape, a pouch shape, a prismatic shape, etc. Furthermore, the lithium-sulfur battery can be used not only as a battery cell used as a power source for a small device, but also as a unit battery for a medium- to large-sized battery module including a plurality of battery cells, and its usage form is not particularly limited.

[0105] In one embodiment of the present invention, a lithium-sulfur battery using a cathode including the sulfur-carbon composite may exhibit excellent effects in terms of battery energy density, but the effects of the present invention are not limited thereto. The lithium-sulfur battery may exhibit an effect of significantly improving energy density by increasing the sulfur loading amount in the electrode and reducing the amount of electrolyte, but the effects of the present invention are not limited thereto.

[0106] The present invention will be described in detail below with reference to examples. However, the examples according to the present invention can be modified in various other forms, and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0107] <Example> Example 1 1) Fabrication of the positive electrode The first polyacrylic acid (weight average molecular weight 450,000) and the second polyacrylic acid (weight average molecular weight 1,250,000) were mixed and then completely neutralized with lithium hydroxide to prepare a lithium-substituted polyacrylic acid as the first binder resin.

[0108] The lithium-substituted polyacrylic acid was mixed with lithium-substituted carboxymethyl cellulose (GL Chem) as a second binder resin and acrylic colloid (acrylic ester copolymer, LG Chem) as a third binder resin to prepare a binder composition, the weight ratios of which are shown in Table 1.

[0109] In addition, sulfur (manufactured by Sigma-Aldrich) was mixed with CNTs (carbon nanotubes) in a mixing ratio of 70:30 using a ball mill, and then heat-treated at 155°C to produce a positive electrode active material, which was a sulfur-carbon composite.

[0110] The binder composition and the positive electrode active material were mixed in a ratio of 4:96 with water as a solvent to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to an aluminum foil current collector and dried at 50°C for 2 hours, achieving a load of 3 mAh / cm. 2 A positive electrode of 1000 kJ / cm2 was produced.

[0111] 2) Lithium-sulfur battery manufacturing As the negative electrode, a lithium foil having a thickness of about 40 μm was used.

[0112] A polyethylene porous membrane (thickness: about 9 μm, porosity: about 40% to 45%) was used as the separation membrane.

[0113] The electrolyte used was a mixture of 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1 wt% lithium nitrate (LiNO3) dissolved in an organic solvent consisting of dioxolane (DOL) and dimethyl ether (DME) in a 1:1 (volume ratio).

[0114] The prepared positive electrode and negative electrode were placed facing each other, the separator was interposed therebetween, and the prepared electrolyte was injected therein to prepare a lithium-sulfur battery.

[0115] Examples 2 to 5 and Comparative Examples 1 to 7 Lithium-sulfur batteries were manufactured in the same manner as in Example 1, except that the weight percentage of the binder resin was changed as shown in Table 1 below when manufacturing the positive electrode.

[0116] However, in Comparative Example 2, the binder composition and the positive electrode active material were added to the water solvent in a ratio of 1:99 and mixed to prepare the positive electrode slurry. In Comparative Example 4, the binder composition and the positive electrode active material were added to the water solvent in a ratio of 3:97, and in Comparative Example 5, the binder composition and the positive electrode active material were added to the water solvent in a ratio of 2.5:97.5 and mixed to prepare the positive electrode slurry.

[0117] Examples 6 and 7 and Comparative Examples 8 to 10 A lithium-sulfur battery was manufactured in the same manner as in Example 1, except that styrene-butadiene rubber was used as the third binder resin when manufacturing the positive electrode, and the weight percentage of the binder resin was changed as shown in Table 1 below.

[0118] [Table 1]

[0119] Measurement of weight average molecular weight The weight average molecular weights of the first binder resin and the second binder resin used in the examples and comparative examples were measured using the following measuring device and conditions.

[0120] GPC measurement device: ACQUITY APC (Waters) Column: PL gel Mixed-B + C (Agilent) Column temperature: RT (20-25°C) Eluent: DMF / 0.05M LiBr Flow rate: 1.0ml / min Detector: Waters 2414 RI detector Sample concentration: ~1mg / ml (0.45μm syringe filter) Injection volume: 10μl Calibration curve: Polystyrene

[0121] Performance evaluation 1.Method of measuring adhesion force The electrode was dried at 50°C for 2 hours and cut into a size of 15cm x 2cm. The electrode surface was then attached to a slide glass with double-sided tape, and a sample for a peel test was prepared by lamination.

[0122] The peel test samples were loaded into a UTM capable of measuring adhesion, and a 90° peel test was performed to measure the peel resistance (gf) and calculate the adhesion of each electrode. The results of the adhesion test are shown in Table 2, and the results of measuring the adhesion depending on the content of the second binder resin, lithium-substituted carboxymethyl cellulose, are shown in Figure 1.

[0123] <Analysis conditions> -Sample width: 20mm - Propagation speed: 300mm / min -Data valid calculation range: 10mm~40mm

[0124] 2. Power density When a 5 Ah pouch cell was fabricated using the batteries manufactured in the Examples and Comparative Examples, the maximum output per weight was measured.

[0125] When the maximum output that can be discharged above the lower limit voltage for 10 seconds at the point where the battery output is at its minimum was determined, the minimum output point for the lithium-sulfur battery used was found to be an SOC (state of charge) of 75. After applying a discharge pulse at 5.0C for 10 seconds at this point, the cell resistance was converted to calculate the maximum output at the lower limit voltage of 1.5V, and this was divided by the weight of the battery to calculate the maximum output per weight (power density).

[0126] FIG. 2 is a graph showing the measurement results of power density for Example 5, Comparative Example 1, and Comparative Example 4, which have different contents of the second binder resin.

[0127] [Table 2]

[0128] From Tables 1 and 2, it can be seen that only when all three types of binder resin layers are combined, excellent adhesive strength and power density can be provided without causing sedimentation.

[0129] From FIG. 1, it can be seen that the adhesive strength increases as the content of the second binder resin increases.

[0130] 2, Comparative Example 1, which contains only the first binder resin, can ensure a high level of power density, but it is difficult to ensure adhesive strength, and Comparative Example 4, which does not contain the first binder resin and contains more than a certain amount of the second binder resin, ensures adhesive strength but reduces power density. Also, if the proportion of the third binder resin is too high, as in Comparative Example 5, settling of the slurry may occur.

Claims

1. a first binder resin, a second binder resin, and a third binder resin; the first binder resin is a lithium-substituted polyacrylic acid; the second binder resin is lithium-substituted carboxymethyl cellulose; The binder composition for a secondary battery electrode, wherein the third binder resin is a colloidal particulate aqueous binder resin.

2. 2. The binder composition for a secondary battery electrode according to claim 1, wherein the first binder resin comprises at least one lithium-substituted polyacrylic acid, and the lithium-substituted polyacrylic acid has a weight average molecular weight (MW) of 300,000 to 1,500,000.

3. The binder composition for a secondary battery electrode according to claim 2 , wherein the first binder resin comprises at least two kinds of lithium-substituted polyacrylic acids having different molecular weights.

4. 2. The binder composition for a secondary battery electrode according to claim 1, wherein a viscosity of a 1.0% aqueous solution of the second binder resin is 100 to 10,000 cP.

5. 2. The binder composition for a secondary battery electrode according to claim 1, wherein the third binder resin is a styrene-butadiene rubber, an acrylic polymer containing a repeating unit derived from at least one acrylic monomer, or a mixture of two or more thereof.

6. 2. The binder composition for a secondary battery electrode according to claim 1, wherein the pH of a 1.0 to 10.0% aqueous solution of the first binder resin and the second binder resin is in the range of 6 to 9.

7. The binder composition for a secondary battery electrode according to claim 1 , further comprising a water-based binder resin as a fourth binder resin.

8. Based on a total of 100% by weight of the binder composition, the first binder resin comprises 5 to 80% by weight, the second binder resin comprises 5 to 80% by weight, The binder composition for a secondary battery electrode according to claim 1 , wherein the third binder resin is contained in an amount of 5 to 80% by weight.

9. 2. The binder composition for a secondary battery electrode according to claim 1, wherein the first binder resin and the second binder resin comprise 20 to 60 wt % based on a total of 100 wt % of the binder composition.

10. The binder composition for a secondary battery electrode according to claim 1 , wherein the third binder resin is present in an amount of 30 to 75 wt % based on 100 wt % of the total binder composition.

11. Based on a total of 100% by weight of the binder composition, the first binder resin comprises 5 to 50% by weight, the second binder resin comprises 5 to 40% by weight, The binder composition for a secondary battery electrode according to claim 1 , wherein the third binder resin is contained in an amount of 30 to 75% by weight.

12. a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material and a binder resin, A positive electrode for a lithium-sulfur secondary battery, wherein the binder resin comprises the binder composition for a secondary battery electrode according to claim 1 .

13. A lithium-sulfur secondary battery comprising the positive electrode of claim 12, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

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