Complex for separator of lithium-sulfur secondary battery, Lithium-sulfur secondary battery separator and Method for manufacturing assembly for separator of lithium-sulfur secondary battery

Abstract

The present invention relates to a composite for a separator of a lithium-sulfur secondary battery, and more specifically, to a composite for a separator of a lithium-sulfur secondary battery having a catalytic function that restricts the movement of higher-order polysulfides and reduces said higher-order polysulfides.

Description

Technology Field

[0001] The present invention relates to a composite for a separator of a lithium-sulfur secondary battery, and more specifically, to a composite for a separator of a lithium-sulfur secondary battery having a catalytic function that restricts the movement of higher-order polysulfides and reduces said higher-order polysulfides. Background Technology

[0003] As the demand for batteries increases for mobile devices, small batteries for the Internet of Things (IoT), battery packs for electric vehicles, and large-capacity energy storage systems for the renewable energy industry, research on next-generation batteries is accelerating.

[0004] Among them, lithium-sulfur batteries (Li-S batteries) are gaining attention as next-generation batteries because they have an energy density five times higher than conventional lithium-ion batteries and use sulfur, which is low-cost and resource-abundant.

[0005] Looking at the principle of a lithium-sulfur battery, it consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During discharge, Li in the negative electrode is oxidized at the negative electrode and moves to the positive electrode active material to combine with sulfur (S8) (reduction reaction of sulfur) to produce lithium polysulfide. The lithium polysulfide is then reduced stepwise from the higher-order lithium polysulfide Li2S8 to the lower-order lithium polysulfide Li2S (S8 → Li2S8 → Li2S6 → Li2S4 → Li2S2 → Li2S), and during charging, Li + Ions move to the cathode, and the polysulfide at the anode is oxidized stepwise from lower-order lithium polysulfide Li2S to higher-order lithium polysulfide Li2S8 (Li2S → Li2S2→ Li2S4→ Li2S6→ Li2S8→ S8)

[0006] Higher-order polysulfide Li2S during the above charging x(4≤ x ≤ 8) has high solubility in the ether-type electrolyte of a Li-S battery, and the polysulfide formed on the cathode active material side creates a concentration gradient. As a result, higher-order polysulfides diffuse beyond the separator and reach the Li-material anode (Shuttle effect), and the lithium polysulfide that reaches the anode corrodes the anode to produce insoluble Li2S / Li2S2 (passivation).

[0007] The insulating low-order lithium polysulfide layer formed on the surface of such a cathode can block the movement of lithium ions, reducing the reaction area of ​​the cathode and increasing internal resistance. Physically, as the low-order lithium polysulfide formed on the cathode grows, it can protrude and form dendrites, damaging the separator and potentially causing an internal short circuit. Additionally, in terms of capacity, it can consume the positive electrode active material (sulfur), leading to a decrease in battery capacity and reduced lifespan.

[0008] Accordingly, in order to solve the above-mentioned problem, the inventors have developed a technology regarding a composite for a lithium-sulfur secondary battery separator having a catalytic function that limits the movement of higher-order polysulfides and reduces them. The problem to be solved

[0010] To solve the above-mentioned problems, the technical objective of the present invention is to provide a composite for a separator of a lithium-sulfur secondary battery comprising an adsorption / reduction structure in which a polysulfide compound adsorbent and a catalyst for reducing polysulfide compounds are attached to part or all of the graphene of a three-dimensional graphene structure including a hollow space.

[0012] To solve the above-mentioned problems, another technical objective of the present invention is to provide a lithium-sulfur secondary battery separator in which the composite for the lithium-sulfur secondary battery separator is coated onto the lithium-sulfur secondary battery separator.

[0014] To solve the above problems, another technical objective of the present invention is to provide a method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, comprising: a step of manufacturing a polymer-graphene mixture by adding a graphene dispersion to a polymer dispersion and mixing to produce a polymer-graphene mixture; a step of manufacturing a first solution by adding a precursor of a polysulfide compound adsorbent to the polymer-graphene mixture and mixing to produce a first solution; a step of manufacturing a second solution by adding a first precursor solution of a catalyst for reducing a polysulfide compound to the first solution and mixing to produce a second solution; a step of manufacturing a structure precursor by adding a second precursor of a catalyst for reducing a polysulfide compound to the second solution, mixing, and then drying to produce a structure precursor; a step of manufacturing a powder by annealing the structure precursor to produce a powder; and a step of manufacturing a slurry by mixing the powder with a binder to produce a slurry.

[0016] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0018] To achieve the above technical objective, one embodiment of the present invention provides a composite for a separator of a lithium-sulfur secondary battery comprising an adsorption / reduction structure in which a polysulfide compound adsorbent and a catalyst for reducing polysulfide compounds are attached to part or all of the graphene of a graphene structure having a three-dimensional structure including a hollow.

[0019] In an embodiment of the present invention, the polysulfide compound is Li2S x It may be characterized by (4≤ x ≤ 8).

[0020] In an embodiment of the present invention, the catalyst for reducing the polysulfide compound is Li2S xLithium polysulfide of (4 ≤ x ≤ 8) Li2S x It may be characterized as a catalyst that reduces to lithium polysulfide of (1 ≤ x ≤ 2).

[0021] In an embodiment of the present invention, the polysulfide compound adsorbent is MoS2, SnS2, Mo2C, black phosphorus, Ni-Co-P, Ni3ZnC 0.7 It may be characterized by being one or more selected from the group consisting of Co3O4, Fe3C, and C3N4.

[0022] In an embodiment of the present invention, the catalyst for reducing the polysulfide compound may be characterized as being one or more selected from the group consisting of NiS, MnS, MnO, TiO2, TiN, VN, WN, WS2, Co3S4, Fe2O3, and La2O3.

[0023] In an embodiment of the present invention, the graphene may be characterized as being N-doped graphene.

[0025] To achieve the above technical objective, another embodiment of the present invention provides a lithium-sulfur secondary battery separator in which a composite for a lithium-sulfur secondary battery separator is coated onto a lithium-sulfur secondary battery separator.

[0027] To achieve the above technical objective, another embodiment of the present invention provides a method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, comprising: a step of manufacturing a polymer-graphene mixture by adding a graphene dispersion to a polymer dispersion and mixing to produce a polymer-graphene mixture; a step of manufacturing a first solution by adding a precursor of a polysulfide compound adsorbent to the polymer-graphene mixture and mixing to produce a first solution; a step of manufacturing a second solution by adding a first precursor solution of a catalyst for reducing a polysulfide compound to the first solution and mixing to produce a second solution; a step of manufacturing a structure precursor by adding a second precursor of a catalyst for reducing a polysulfide compound to the second solution, mixing, and then drying to produce a structure precursor; a step of manufacturing a powder by annealing the structure precursor to produce a powder; and a step of manufacturing a slurry by mixing the powder with a binder to produce a slurry.

[0028] In an embodiment of the present invention, the graphene may be characterized as being N-doped graphene.

[0029] In an embodiment of the present invention, the polymer may be characterized as being one or more selected from the group consisting of polystyrene, polypropylene, polyethylene, and polyacrylonitrile.

[0030] In an embodiment of the present invention, the precursor of the polysulfide compound adsorbent may be characterized as being a molybdenum sulfide salt.

[0031] In an embodiment of the present invention, the precursor of the polysulfide compound adsorbent is (NH4)2MoS4, (NH4)6Mo7O 24 It may be characterized by being one or more selected from the group consisting of Na2MoO4.

[0032] In an embodiment of the present invention, the first precursor solution of the catalyst for reducing the polysulfide compound may be characterized as a solution comprising one or more selected from the group consisting of nickel salt, manganese salt, titanium salt, vanadium salt, tungsten salt, cobalt salt, and iron salt.

[0033] In an embodiment of the present invention, the first precursor solution of the catalyst for reducing the polysulfide compound may be characterized as a solution comprising one or more selected from the group consisting of nickel nitrate, manganese nitrate, titanium nitrate, vanadium nitrate, tungsten nitrate, cobalt nitrate, and iron nitrate.

[0034] In an embodiment of the present invention, the second precursor of the catalyst for reducing the polysulfide compound may be characterized as being one or more selected from the group consisting of thiourea, urea, and thioacetamide.

[0035] In an embodiment of the present invention, the annealing of the powder manufacturing step may be characterized by comprising: a first annealing step of first annealing at 400 to 600°C; and a second annealing step of second annealing at 700 to 1200°C.

[0036] In an embodiment of the present invention, the binder in the slurry preparation step may be characterized as being one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polystyrene-co-butadiene (SBR), and carboxymethyl cellulose (CMC). Effects of the invention

[0038] According to an embodiment of the present invention, the composite for the separator of the lithium-sulfur secondary battery has the performance of limiting the diffusion of polysulfides and reducing higher-order polysulfides to lower-order polysulfides to suppress the shuttle effect, thereby improving the capacity, lifespan, and stability of the Li-S battery.

[0040] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims. Brief explanation of the drawing

[0042] FIG. 1 is a schematic diagram showing the synthesis process of a NiS2-MnS / MoS2-3DNGr hybrid according to one embodiment of the present invention. FIG. 2 is a diagram showing the structural analysis of a NiS2-MnS / MoS2-3DNGr hybrid membrane manufactured according to an embodiment of the present invention. Specifically, FIG. 2 (a) to (c) are SEM images of the NiS2-MnS / MoS2-3DNGr hybrid, and the inset of (a) is the EDAX pattern of the NiS2-MnS / MoS2-3DNGr hybrid. (d) and (e) are TEM images of the NiS2-MnS / MoS2-3DNGr hybrid. (f) and (g) are HR-TEM images of the MoS2NS and NiS2-MnS NP regions. (h) is STEM, and (i) to (n) are EDS mapping images of the NiS2-MnS / MoS2-3DNGr hybrid. FIG. 3 is another figure showing the structural analysis of a NiS2-MnS / MoS2-3DNGr hybrid membrane manufactured according to one embodiment of the present invention. Specifically, FIG. 3(a) is the N2 adsorption / desorption curve of the NiS2-MnS / MoS2-3DNGr hybrid, and the inset of (a) shows the pore size distribution of NiS2-MnS / MoS2-3DNGr. (b) is the XRD pattern of NiS2-MnS / MoS2-3DNGr, MoS2-3DNGr, and 3DNGr. (c) is the XPS irradiation spectrum of the NiS2-MnS / MoS2-3DNGr hybrid. (d) to (i) are high-resolution XPS spectra of C 1s, N 1s, Mo 3d, S 2p, Ni 2p, and Mn 2p for the NiS2-MnS / MoS2-3DNGr hybrid. FIG. 4 is a diagram showing the performance analysis of a NiS2-MnS / MoS2-3DNGr hybrid membrane according to an embodiment of the present invention. Specifically, FIG. 4(a) is a digital photograph of other membranes. (b) is a digital photograph of a NiS2-MnS / MoS2-3DNGr-modified membrane in a bent and folded state. (c) is a planar SEM image of a Celgard membrane, and the inset of (c) is a planar SEM image of the Celgard membrane at high magnification. (d) and (e) are planar SEM images of a NiS2-MnS / MoS2-3DNGr-modified membrane, and the inset of (e) is a high-magnification planar SEM image of a NiS2-MnS / MoS2-3DNGr-modified membrane. (f) and (g) are cross-sectional SEM images of a NiS2-MnS / MoS2-3DNGr-modified membrane. (h) to (m) are EDS mapping images of NiS2-MnS / MoS2-3DNGr-modified membranes. (n) is the UV-Vis spectrum of Li2S6 before and after absorption by the developed coating material, and the inset in (n) shows polysulfide adsorption tests for (1) Li2S6 solution, (2) 3DNGr, (3) MoS2-3DNGr, and (4) NiS2-MnS / MoS2-3DNGr, respectively. (o) is a permeation test of the NiS2-MnS / MoS2-3DNGr-modified membrane for 15 hours, and (p) is a permeation test of the Celgard membrane for 15 hours. FIG. 5 is a diagram showing the electrical characteristics of a NiS2-MnS / MoS2-3DNGr hybrid catalyst according to one embodiment of the present invention. Specifically, FIG. 5(a) shows open-circuit potential curves representing self-discharge characteristics ((1): NiS2-MnS / MoS2-3DNGr-modified separator, (2) MoS2-3DNGr-modified separator, (3) 3DNGr-modified separator, (4) Celgard separator). (b) shows the charge-discharge curve of a Li-S battery cycled at 0.1C and the corresponding self-discharge characteristics of a cell using the NiS2-MnS / MoS2-3DNGr-modified separator. (c) shows the lithium ion transfer number of the NiS2-MnS / MoS2-3DNGr-modified separator and the Celgard separator. (d) and (e) show the CV curves at various voltage scan rates and the corresponding linear fit of the peak current of the Li-S battery with the NiS2-MnS / MoS2-3DNGr-modified separator. (f) shows the EIS spectrum of the developed material in a symmetric cell with Li2S6 in the electrolyte ((1): NiS2-MnS / MoS2-3DNGr, (2) MoS2-3DNGr, (3) 3DNGr). (g) is 5 mV s⁻¹ -1 This shows the CV curves of the NiS2-MnS / MoS2-3DNGr material in symmetric cells with and without Li2S6 in the electrolyte at a scan rate of . (h) is 5 mV s⁻¹. -1 (i) shows the CV curve of the material developed in a symmetric cell with Li2S6 in the electrolyte at scan rate . (i) shows the CV curve of the NiS2-MnS / MoS2-3DNGr material in a symmetric cell with Li2S6 in the electrolyte at different scan rates. Specific details for implementing the invention

[0043] The present invention will be described below with reference to the attached drawings. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0044] Throughout the specification, when it is stated that a part is "connected (connected, in contact, combined)" with another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members interposed between them. Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but rather allows for the inclusion of additional components. Additionally, "molar weight part" refers to the relative moles of another constituent material with respect to the moles of a reference material. In this case, the reference material may be one of the constituent materials.

[0046] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0048] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0050] To achieve the aforementioned technical objectives, one embodiment of the present invention provides a composite for a separator of a lithium-sulfur secondary battery comprising an adsorption / reduction structure in which a polysulfide compound adsorbent and a catalyst for reducing polysulfide compounds are attached to part or all of the graphene of a three-dimensional graphene structure including a hollow structure. By including the adsorption / reduction structure in which a polysulfide compound adsorbent and a catalyst for reducing polysulfide compounds are attached to part or all of the graphene of the three-dimensional graphene structure including a hollow structure, the low reaction area can be improved and adsorption and reduction of polysulfide compounds can be enabled.

[0051] In an embodiment of the present invention, the polysulfide compound is Li2S x It may be characterized by (4≤ x ≤ 8).

[0052] In an embodiment of the present invention, the catalyst for reducing the polysulfide compound is Li2S x Lithium polysulfide of (4 ≤ x ≤ 8) Li2S x It may be characterized as a catalyst that reduces to lithium polysulfide (1 ≤ x ≤ 2). The above Li2S x A higher-order polysulfide compound (4 ≤ x ≤ 8) is reduced to a lower-order polysulfide compound, Li2S, by a catalyst for the reduction of the polysulfide compound. x It can be reduced to (1 ≤ x ≤ 2).

[0053] In an embodiment of the present invention, the polysulfide compound adsorbent is MoS2, SnS2, Mo2C, black phosphorus, Ni-Co-P, Ni3ZnC 0.7 It may be characterized by being one or more selected from the group consisting of Co3O4, Fe3C, and C3N4.

[0054] In an embodiment of the present invention, the catalyst for reducing the polysulfide compound may be characterized as being one or more selected from the group consisting of NiS, MnS, MnO, TiO2, TiN, VN, WN, WS2, Co3S4, Fe2O3, and La2O3.

[0055] In an embodiment of the present invention, the graphene may be characterized as being N-doped graphene. Since the graphene is N-doped graphene, it forms an electron pathway to rapidly move electrons to a catalytic site, thereby accelerating the oxidation / reduction reaction.

[0058] To achieve the above technical objective, another embodiment of the present invention provides a lithium-sulfur secondary battery separator in which the composite for the lithium-sulfur secondary battery separator is coated onto the lithium-sulfur secondary battery separator. The lithium-sulfur secondary battery separator may be a commercially available separator and, preferably, may be Celgard 2400.

[0060] To achieve the above technical objective, another embodiment of the present invention provides a method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, comprising: a step of manufacturing a polymer-graphene mixture by adding a graphene dispersion to a polymer dispersion and mixing to produce a polymer-graphene mixture; a step of manufacturing a first solution by adding a precursor of a polysulfide compound adsorbent to the polymer-graphene mixture and mixing to produce a first solution; a step of manufacturing a second solution by adding a first precursor solution of a catalyst for reducing a polysulfide compound to the first solution and mixing to produce a second solution; a step of manufacturing a structure precursor by adding a second precursor of a catalyst for reducing a polysulfide compound to the second solution, mixing, and then drying to produce a structure precursor; a step of manufacturing a powder by annealing the structure precursor to produce a powder; and a step of manufacturing a slurry by mixing the powder with a binder to produce a slurry.

[0061] FIG. 1 is a schematic diagram showing the synthesis process of a NiS2-MnS / MoS2-3DNGr hybrid according to one embodiment of the present invention.

[0062] Referring to FIG. 1, graphene is formed on the polymer through the polymer-graphene mixture preparation step, thereby improving the low reaction area and non-conductivity. Additionally, NiS2-MnS and MoS2 can be attached to the graphene formed on the polymer through the first solution preparation step and the second solution preparation step to improve the reaction area and suppress aggregation. The polymer can be vaporized and removed through annealing in the powder preparation step.

[0063] In an embodiment of the present invention, the graphene may be characterized as being N-doped graphene. Since the graphene is N-doped graphene, it forms an electron pathway to rapidly move electrons to a catalyst site, thereby accelerating the oxidation / reduction reaction. Through the slurry preparation step, the composite for the separator of the lithium-sulfur secondary battery can be coated onto the lithium-sulfur secondary battery separator.

[0064] In an embodiment of the present invention, the polymer may be characterized as being one or more selected from the group consisting of polystyrene, polystyrene, polypropylene, polyethylene, and polyacrylonitrile.

[0065] In an embodiment of the present invention, the precursor of the polysulfide compound adsorbent may be characterized as being a molybdenum sulfide salt.

[0066] In an embodiment of the present invention, the precursor of the polysulfide compound adsorbent is (NH4)2MoS4, (NH4)6Mo7O 24 It may be characterized by being one or more selected from the group consisting of Na2MoO4.

[0067] In an embodiment of the present invention, the first precursor solution of the catalyst for reducing the polysulfide compound may be characterized as a solution comprising one or more selected from the group consisting of nickel salt, manganese salt, titanium salt, vanadium salt, tungsten salt, cobalt salt, and iron salt.

[0068] In an embodiment of the present invention, the first precursor solution of the catalyst for reducing the polysulfide compound may be characterized as a solution comprising one or more selected from the group consisting of nickel nitrate, manganese nitrate, titanium nitrate, vanadium nitrate, tungsten nitrate, cobalt nitrate, and iron nitrate.

[0069] In an embodiment of the present invention, the second precursor of the catalyst for reducing the polysulfide compound may be characterized as being one or more selected from the group consisting of thiourea, urea, and thioacetamide.

[0070] In an embodiment of the present invention, the annealing of the powder manufacturing step may be characterized by comprising: a first annealing step of first annealing at 400 to 600°C; and a second annealing step of second annealing at 700 to 1200°C. The polymer can be removed by vaporizing it through the annealing, and the polymer can be removed by vaporizing it through the first annealing and the second annealing.

[0072] In an embodiment of the present invention, the binder in the slurry preparation step may be characterized as being one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polystyrene-co-butadiene (SBR), and carboxymethyl cellulose (CMC).

[0074] The embodiments described above will be explained in more detail through the following examples or experimental examples. However, the following examples or experimental examples are for illustrative purposes only and are not intended to limit the scope.

[0076] Example 1: Composite for separator of lithium-sulfur secondary battery (hereinafter "NiS 2 -MnS / MoS 2 Method for manufacturing a separator coated with “-3DNGr hybrid”

[0078] [ Step 1: Reaction Solution No. 1; Preparation of Polystyrene (PS) - Graphene Oxide (GO) Dispersion ]

[0079] Solution A is prepared by dispersing 0.24g of PS in 20ml of 99.9% ethanol, and Solution B is prepared by dispersing 0.06g of GO in 60ml of distilled water. Then, Solution B is slowly added dropwise to Solution A while it is being stirred, and the mixture is stirred for 5 hours. After that, 40.02g of (NH4)2MoS is added and the mixture is stirred for 5 hours.

[0081] [ Step 2: Reaction Solution No. 2; Preparation of Polystyrene (PS) - Graphene Oxide (GO) Dispersion ]

[0082] 0.025g of Ni(NO3)2.6H2O and 0.025g of Mn(NO3)24H2O are added to 5ml of distilled water and stirred.

[0084] [ Step 3: Precursor Manufacturing ]

[0085] Solution 1 and Solution 2 are mixed and transferred to a 2-neck flask. After stirring at 60°C for 12 hours, 0.15g of thiourea is added to the mixture of Solution 1 and Solution 2 and stirred for 30 minutes. Subsequently, the mixture is freeze-dried prior to the Chemical Vapor Deposition (CVD) Annealing process described below.

[0087] [ Step 4: CVD Process; Preparation of NiS2-MnS / MoS2-3DNGr Hybrid Powder ]

[0088] In step 1, maintain in an Ar / H2 mixed gas atmosphere at 500°C for 1 hour, and in step 2, maintain in an Ar gas atmosphere at 900°C for 3 hours.

[0090] [ Step 5: Membrane Manufacturing ]

[0091] To prepare a homogeneous NiS2-MnS / MoS2-3DNGr hybrid sludge, 80 mg of 4-step NiS2-MnS / MoS2-3DNGr hybrid powder and 20 mg of PVDF binder are added to an NPM solution and stirred for 12 hours to prepare the sludge. The prepared sludge is applied to a carbon-coated conductive aluminum foil, dried, and then cut into an appropriate separator size for battery manufacturing.

[0093] Composite for the separator of the above-mentioned lithium-sulfur secondary battery (hereinafter "NiS 2 -MnS / MoS 2 Performance of separator coated with “-3DNGr hybrid”

[0094] Li-S battery using NiS2-MnS / MoS2-3DNGr coated Celgard separator (1.0 mg / cm²) 2 The S loading) exhibited a high initial capacity of 1011 mAh / g at a current rate of 0.1C and showed a low capacity degradation of about 0.12% per cycle over 200 repeated cycles.

[0095] The developed Li-S battery exhibited an excellent specific capacity of 656.8 mAh / g even when the current rate increased to 3C (122.8 mAh / g higher than the commercial Celgard separator). It also showed a maximum of 550.1 mAh after 200 cycles of repeated charge-discharge testing.

[0096] The separator of the present invention and 2.52 mg / cm² 2 The lithium-sulfur battery with detected sulfur had an excellent capacity of 798 mAh / g and operated favorably even in repeated tests at a high current rate (3C). In the case of repeated tests, it showed a low capacity decrease of 0.035% per cycle and maintained a Coulomb efficiency of 99.65% during 1,000 repetitions.

[0099] Experimental Example 1: Prepared NiS 2 -MnS / MoS 2 Structural analysis of the -3DNGr hybrid membrane

[0100] To analyze the structure of the above-prepared NiS2-MnS / MoS2-3DNGr hybrid membrane, surface microstructure observation, compositional analysis, and binding energy analysis were performed using field emission scanning electron microscopy (FESEM), bio-emission spectroscopy (BET), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The measurement results are shown in Figures 2 and 3.

[0101] FIG. 2 is a diagram showing the structural analysis of a NiS2-MnS / MoS2-3DNGr hybrid membrane manufactured according to an embodiment of the present invention. Specifically, FIG. 2 (a) to (c) are SEM images of the NiS2-MnS / MoS2-3DNGr hybrid, and the inset of (a) is the EDAX pattern of the NiS2-MnS / MoS2-3DNGr hybrid. (d) and (e) are TEM images of the NiS2-MnS / MoS2-3DNGr hybrid. (f) and (g) are HR-TEM images of the MoS2NS and NiS2-MnS NP regions. (h) is STEM, and (i) to (n) are EDS mapping images of the NiS2-MnS / MoS2-3DNGr hybrid.

[0102] Referring to Figure 2, (a–c) indicate the presence of component elements of the NiS2-MnS / MoS2-3DNGr hybrid through EDAX patterns. (d–e) are TEM images, and (f–g) show each component element in detail using HR-TEM. (h–n) show the compositional distribution of each component material in the same images.

[0103] Through Figure 2, it can be confirmed that the NiS2-MnS / MoS2-3DNGr hybrid catalyst was successfully produced through the above process.

[0104] FIG. 3 is another figure showing the structural analysis of a NiS2-MnS / MoS2-3DNGr hybrid membrane manufactured according to one embodiment of the present invention. Specifically, FIG. 3(a) is the N2 adsorption / desorption curve of the NiS2-MnS / MoS2-3DNGr hybrid, and the inset of (a) shows the pore size distribution and specific surface area of ​​NiS2-MnS / MoS2-3DNGr. (b) is the XRD pattern of NiS2-MnS / MoS2-3DNGr, MoS2-3DNGr, and 3DNGr. (c) is the XPS irradiation spectrum of the NiS2-MnS / MoS2-3DNGr hybrid. (d) to (i) are high-resolution XPS spectra of C 1s, N 1s, Mo 3d, S 2p, Ni 2p, and Mn 2p for the NiS2-MnS / MoS2-3DNGr hybrid.

[0105] Referring to Figure 3, it can be confirmed that each component of the NiS2-MnS / MoS2-3DNGr hybrid membrane is present.

[0107] Experimental Example 2: Performance Analysis of NiS2-MnS / MoS2-3DNGr Hybrid Membrane

[0108] To analyze the performance of the above-prepared NiS2-MnS / MoS2-3DNGr hybrid membrane, the membrane was repeatedly folded and bent, and the surface and cross-section were observed using a scanning electron microscope (SEM). Simultaneously, the locations of the constituent elements were overlaid and image mapped using EDS. The measurement results are shown in Figure 4.

[0109] Referring to Fig. 4, (a~b) shows a Celgard 2400 membrane coated with NiS2-MnS / MoS2-3DNGr, and it can be seen that it remains flexible even after coating and is not damaged even after repeated folding and bending. (c~f) shows the morphology captured via SEM, and (g~m) shows the distribution of each component element at specific locations in the image in color using EDS mapping. Through this, it can be confirmed that each component element of the synthesized catalyst is evenly distributed. (n) is data comparing the absorption capacity of the NiS2-MnS / MoS2-3DNGr hybrid for polysulfides, and it can be seen that compared to the Li2S6 solution (1) before treatment, the solution (4) containing the developed catalyst absorbed polysulfides in the solution and became transparent.

[0110] (o~p) represents the extent to which polysulfides pass through the membranes for the NiS2-MnS / MoS2-3DNGr hybrid membrane and the control group (Celgard 2400) membrane. It can be seen that the NiS2-MnS / MoS2-3DNGr hybrid membrane (o) inhibited the passage of polysulfides over time, whereas the control group (p) allowed polysulfides on the right to pass through the membrane and move to the left after 15 hours.

[0111] Through this, it can be confirmed that the NiS2-MnS / MoS2-3DNGr hybrid membrane absorbs polysulfides in the electrolyte and blocks their movement through the membrane.

[0113] Experimental Example 3: NiS 2 -MnS / MoS 2 Electrical characteristics of the -3DNGr hybrid (hereinafter referred to as the "developed catalyst")

[0114] Electrochemical analysis was performed to analyze the electrical characteristics of the above-prepared NiS2-MnS / MoS2-3DNGr hybrid. The measurement results are shown in Figure 5.

[0115] Referring to FIG. 5, the electrical characteristics of the developed catalyst are evaluated. The self-discharge characteristics are shown by the Open circuit potential curve in (a), and it can be confirmed that the developed catalyst (1) maintained stable performance compared to the control group (4). (b) shows the charge / discharge curve after 15 hours have passed since the first cycle, and it can be confirmed that it decreased slightly when repeated. (c) is data measuring the degree of lithium ion passage through current, indicating that lithium passes through similarly to the control group. This means that the flow of current is not obstructed during the charge / discharge process. (d~e) show the change in current when the voltage changes at a constant rate using cyclic voltametry, and it can be confirmed that a constant pattern was maintained. (f) shows the impedance of the developed catalyst in a lithium polysulfide solution, and the final synthesized catalyst (1) shows a low impedance.

[0117] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0118] The scope of the present invention is defined by the claims set forth below, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 The adsorption / reduction structure comprises a polysulfide compound adsorbent and a catalyst for reducing polysulfide compounds attached to part or all of the graphene of a graphene structure having a three-dimensional structure including a hollow, wherein the polysulfide compound adsorbent is MoS2, SnS2, Mo2C, black phosphorus, Ni-Co-P, Ni3ZnC 0.7 A composite for a separator of a lithium-sulfur secondary battery, characterized by being one or more selected from the group consisting of Co3O4, Fe3C, and C3N4. Claim 2 In claim 1, the polysulfide compound is Li2S x A composite for a separator of a lithium-sulfur secondary battery characterized by (4 ≤ x ≤ 8). Claim 3 In claim 1, the catalyst for reducing the polysulfide compound is Li2S x Lithium polysulfide of (4 ≤ x ≤ 8) Li2S x A composite for a separator of a lithium-sulfur secondary battery, characterized by being a catalyst that reduces to lithium polysulfide of (1 ≤ x ≤ 2). Claim 4 delete Claim 5 A composite for a separator of a lithium-sulfur secondary battery, comprising an adsorption / reduction structure in which a polysulfide compound adsorbent and a catalyst for reducing a polysulfide compound are attached to part or all of the graphene of a graphene structure having a three-dimensional structure including a hollow, wherein the catalyst for reducing a polysulfide compound is one or more selected from the group consisting of NiS, MnS, MnO, TiO2, TiN, VN, WN, WS2, Co3S4, Fe2O3, and La2O3. Claim 6 A composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 1, the graphene is N-doped graphene. Claim 7 A lithium-sulfur secondary battery separator coated with the lithium-sulfur secondary battery separator composite of claim 1. Claim 8 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, comprising: a step of manufacturing a polymer-graphene mixture by adding a graphene dispersion to a polymer dispersion and mixing to produce a polymer-graphene mixture; a step of manufacturing a first solution by adding a precursor of a polysulfide compound adsorbent to the polymer-graphene mixture and mixing to produce a first solution; a step of manufacturing a second solution by adding a first precursor solution of a catalyst for reducing a polysulfide compound to the first solution and mixing to produce a second solution; a step of manufacturing a structure precursor by adding a second precursor of a catalyst for reducing a polysulfide compound to the second solution, mixing, and then drying to produce a structure precursor; a step of manufacturing a powder by annealing the structure precursor to produce a powder; and a step of manufacturing a slurry by mixing the powder with a binder to produce a slurry. Claim 9 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the graphene is N-doped graphene. Claim 10 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the polymer is one or more selected from the group consisting of polystyrene, polypropylene, polyethylene, and polyacrylonitrile. Claim 11 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the precursor of the polysulfide compound adsorbent is a molybdenum sulfide salt. Claim 12 In claim 8, the precursor of the polysulfide compound adsorbent is (NH4)2MoS4, (NH4)6Mo7O 24 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized by being one or more selected from the group consisting of , , and Na2MoO4. Claim 13 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the first precursor solution of the catalyst for reducing the polysulfide compound is a solution comprising one or more selected from the group consisting of nickel salt, manganese salt, titanium salt, vanadium salt, tungsten salt, cobalt salt, and iron salt. Claim 14 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the first precursor solution of the catalyst for reducing the polysulfide compound is a solution comprising one or more selected from the group consisting of nickel nitrate, manganese nitrate, titanium nitrate, vanadium nitrate, tungsten nitrate, cobalt nitrate, and iron nitrate. Claim 15 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the second precursor of the catalyst for reducing the polysulfide compound is one or more selected from the group consisting of thiourea, urea, and thioacetamide. Claim 16 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery, characterized in that, in claim 8, the annealing of the powder manufacturing step comprises a first annealing step of first annealing at 400 to 600°C; and a second annealing step of second annealing at 700 to 1200°C. Claim 17 A method for manufacturing a composite for a separator of a lithium-sulfur secondary battery according to claim 8, characterized in that, in the slurry manufacturing step, the binder is one or more selected from the group consisting of PVDF, PTFE, PEO, SBR, and CMC.

Images