Lithium-sulfur battery cathode using a fabric material, lithium-sulfur battery comprising the same, and method of manufacturing the same

Abstract

The present invention provides a method for preparing a lithium-sulfur battery cathode using a fabric material, characterized in that it includes: a step of preparing a conductive support by carbonizing the fabric material through heat treatment; a step of electroplating a conductive metal material on the conductive support; a step of loading the electroplated conductive support containing the sulfur polymer and a first carbon material modified by a first functional group capable of hydrogen bonding with the sulfur polymer; and a step of loading a second carbon material modified by a second functional group capable of layer-by-layer self-assembly with the first carbon material to form a capping layer on the conductive support.

Description

Technical Field

[0001] This invention relates to a lithium-sulfur battery cathode using fabric materials, a lithium-sulfur battery containing the same, and a method for preparing the same. More specifically, it relates to a lithium-sulfur battery cathode using fabric materials with high sulfur loading and excellent electrical properties, a lithium-sulfur battery containing the same, and a method for preparing the same. Background Technology

[0002] Electrodes, catalysts, adsorbents, sensors, and other components all have structures in which conductive materials, such as metals, are contained on a support as active substances. In such cases, excellent conductivity of the support, high specific surface area of ​​both the support and the conductive active material, and ease of processing are required.

[0003] Therefore, this paper proposes an electrode and its preparation method that directly uses carbon nanotubes, graphene and other carbon supports as supports.

[0004] For example, Korean Patent Publication No. 10-2009-0041637 discloses a polyimide carbon nanofiber electrode that can reduce the diameter of carbon fibers, and Korean Patent Publication No. 10-2017-0080159 discloses an electrode based on carbon fiber fabric / metal oxide nanowires for energy storage devices and its preparation method.

[0005] However, these methods of directly using carbon supports require the preparation of carbon-based supports, which necessitates the additional preparation of carbon-based materials.

[0006] As an alternative, research is actively underway on using fabric materials as supports. For example, when used as electrodes, fabric materials can not only increase the loading of active materials due to their high porosity and internal surface area, but also serve as effective structures for smooth particle movement. Therefore, research has been reported on imparting conductivity to insulating fabric materials to prepare porous electrodes and applying them to high-performance energy storage devices.

[0007] As an energy storage device, lithium-sulfur batteries have been actively researched as a potential next-generation energy storage device due to their high theoretical energy density. However, lithium-sulfur batteries suffer from low driving stability due to the low conductivity of sulfur as the positive electrode material, volume expansion during operation, and sulfur loss (shuttle effect) caused by irreversible reactions.

[0008] To overcome the above-mentioned drawbacks, research is actively underway to electropolarize conductive materials that have physical / chemical bonding with sulfur by mixing them with sulfur, but studies conducted on flat plates have shown that the loading of sulfur is limited.

[0009] From this perspective, in order to overcome the limitations of conductivity and ionic conductivity caused by the increase in the amount of active material loaded in the current collector and to achieve high-density energy capacity and output characteristics per unit volume / area, it is necessary to develop electrodes with excellent conductivity and high surface area.

[0010] In the fabrication of porous current collectors, while fabric materials can not only increase the loading of active materials due to their high porosity and internal surface area, but are also effective structures for smooth ion movement, they also possess insulating properties. Therefore, research has been reported on imparting conductivity to insulating fabric materials to fabricate porous electrodes and applying them to high-performance energy storage devices.

[0011] However, many applications struggle to fabricate effective porous current collectors for high-performance energy storage devices for several reasons. First, while existing commercially available porous metallic current collectors offer high conductivity, they are not only too heavy in terms of material weight, but also limited by porosity and internal surface area. Furthermore, the large-scale fabrication of electrodes is constrained by the use of strong acid etching processes and their high cost. Carbon-based porous electrodes, made by coating conductive carbon materials such as carbon nanotubes (CNTs) or graphene onto fabrics, not only exhibit lower conductivity than metallic materials but also suffer from reduced electrochemical stability.

[0012] On the other hand, when using electroless deposition to coat fabric materials, it is not only difficult to uniformly coat the internal fibrillary structure of the fabric material, but also difficult to effectively utilize the surface area of ​​the porous structure due to agglomeration. Furthermore, since impurities are introduced during surface treatment and reduction, the conductivity and mechanical stability of the electrode are ultimately limited.

[0013] Furthermore, when additionally coating metal nanoparticles, it is difficult to impart metal-like conductivity to the bulk due to insufficient knowledge about interparticle interface treatment and interparticle interface impedance. This results in the disadvantage that the additional surface treatment process required to overcome this problem prolongs the entire electrode fabrication process time. Summary of the Invention

[0014] Technical issues

[0015] Therefore, the technical problem to be solved by the present invention is to prepare a porous current collector that can maintain the excellent network characteristics of the fabric while giving the fabric material excellent conductivity, mechanical stability and high specific surface area, and to provide a method for preparing a lithium-sulfur battery cathode that can improve the low conductivity and utilization efficiency, which are the inherent problems of lithium-sulfur battery cathodes, by coating the electrode with a conductive coating layer (protective layer) while increasing the sulfur loading based on this.

[0016] Technical solution

[0017] To address the above problems, the present invention provides a method for preparing a lithium-sulfur battery cathode using fabric materials, characterized by comprising:

[0018] The step of preparing a conductive support by carbonizing the fabric material through heat treatment;

[0019] The steps of electroplating a conductive metal material onto the conductive support and loading a slurry comprising the sulfur polymer and a first carbon material modified by a first functional group capable of hydrogen bonding with the sulfur polymer onto the electroplated conductive support.

[0020] The step of loading a second carbon material modified by a second functional group onto the conductive support to form a capping layer, which is capable of self-assembling in layers with the first carbon material.

[0021] An embodiment of the present invention is characterized in that the carbon material is a carbon nanotube, the first functional group is an amino group, and the second functional group is a carboxyl group.

[0022] Another embodiment of the present invention is characterized in that the heat treatment is carried out in the range of 600°C to 2000°C, and the carbon support prepared by the heat treatment retains the network structure of the fabric material as is.

[0023] Another embodiment of the present invention is characterized in that the conductive material comprises one or more selected from the group consisting of nickel (Ni), copper (Cu), and aluminum (Al).

[0024] Another embodiment of the present invention is characterized in that the above-mentioned fabric material is a fabric containing carbon atoms in the main chain.

[0025] Furthermore, the present invention provides a lithium-sulfur battery cathode, comprising: a carbon support having a network structure of woven material; a conductive metal material coated on the carbon support; a sulfur polymer loaded on the conductive metal material; a first carbon material modified by a first functional group bonded to the sulfur polymer; and a second carbon material bonded to the first carbon material to form a capping layer.

[0026] One example of the present invention is characterized in that the above-mentioned lithium-sulfur battery cathode is prepared by the above-mentioned method.

[0027] Another embodiment of the present invention is characterized in that the carbon material is a carbon nanotube, the first functional group is an amino group, and the second functional group is a carboxyl group.

[0028] Another embodiment of the present invention is characterized in that the conductive material comprises one or more selected from the group consisting of Ni, Cu, and Al.

[0029] In addition, the present invention also provides a lithium-sulfur battery comprising the above-mentioned lithium-sulfur battery cathode.

[0030] The effects of the invention

[0031] According to the present invention, a carbon support with excellent conductivity and high porosity network structure can be prepared by heat-treating the fabric material at a low temperature of 600°C. Then, a porous conductive structure with excellent electromechanical strength and outstanding porosity can be prepared by coating a metallic active material using a simple electroplating method. In particular, the electrode body prepared according to the present invention can achieve high energy density per unit area and fast charge / discharge speed due to the increased sulfur loading by utilizing the high surface area and excellent electron transport characteristics of the porous current collector, thereby improving the energy density and driving stability of lithium-sulfur batteries.

[0032] Furthermore, after preparing MWCNTs with amine groups (NH2) through surface modification of multi-walled carbon nanotubes (MWCNTs), these MWCNTs were mixed with sulfur polymers (S-poly) to prepare a slurry (HS) for loading inside the current collector without the need for an insulating polymer binder. NH2-MWCNTs improve the conductivity of the S-poly layer, and the -NH2 groups effectively increase the utilization efficiency of S-poly through their binding force with the irreversibly moving lithium polysulfide in the drive, thereby increasing the energy density. Then, MWCNTs with carboxyl groups (COOH) were prepared, and a layered self-assembly method based on the mutual hydrogen bonding force with NH2-MWCNTs was used to coat the surface of the slurry loaded on the electrode with multiple layers to form a capping layer (CL), thereby further improving the drive stability by preventing the shuttle effect of S-poly in the drive.

[0033] Furthermore, the present invention increases the loading of active material while ensuring smooth ion migration by leveraging the high porosity and wide surface area of ​​the support structure, which has a network structure of fabric material. This makes the conductive structure of the present invention suitable not only for energy storage devices, but also for various electronic devices (e.g., sensors) or catalysts that require thin porous structures. Moreover, the present invention, which prepares conductive structures by simple electroplating, has the advantage that the size or shape of the structure to be prepared is not limited. Attached Figure Description

[0034] Figure 1 This diagram illustrates the steps of a method for preparing a porous conductive structure (EP-CT) based on fabric material according to an embodiment of the present invention.

[0035] Figure 2This is a schematic diagram illustrating the preparation of the porous conductive current collector according to the above embodiments of the present invention and its use as the positive electrode of a lithium-sulfur battery.

[0036] Figure 3 shows the surface impedance values ​​of the carbon support (C-CT) formed according to the heat treatment temperature. Figure 3a ) and scanning electron microscope (SEM) images of carbon supports that retain their porous structure after heat treatment at 700 degrees Celsius. Figure 3b ).

[0037] Figure 4 shows a scanning electron microscope (SEM) image of the electroplating apparatus used in this embodiment and the support structure coated with metal over time. Figure 4a ) and photos before / after coating ( Figure 4b ).

[0038] Figure 5 The X-ray diffraction (XRD) results are shown for the porous conductive structure and the commercially available porous nickel support of this invention.

[0039] Figure 6 The results were obtained to determine the changes in the electrical properties of the carbon support over time.

[0040] Figure 7 and Figure 8 The images shown are scanning electron microscope (SEM) and elemental mapping images of the electroplated porous conductive structure of the present invention. Figure 7 Scanning electron microscope and elemental distribution images of the conductive structure of the electroless electroplated fabric material support. Figure 8 ).

[0041] Figure 9 and Figure 10 These are scanning electron microscope images of the porous conductive structure of the present invention. Figure 9 Scanning electron microscope images of commercially available porous nickel supports. Figure 10 ).

[0042] Figure 11 To load 3 mg / cm³ onto an electroplated porous conductive structure (EP-CT) via a slurry impregnation method 2 5mg / cm 2 8mg / cm 2 EP-CT / HS scanning electron microscopy and elemental distribution images of sulfur polymers (S-poly).

[0043] Figure 12 To use interlayer self-assembly in Figure 11 A schematic diagram and a detailed diagram showing the bonding of EP-CT / HS to form EP-CT / HS / CL by coating a conductive carbon overlay.

[0044] Figure 13 EP-CT / HS / CL cathode (S-poly loading: 3 mg / cm³) 2 The results of cyclic voltametry (CV) determination.

[0045] Figures 14 to 15 For an S-poly loading of 3 mg / cm³ 2 The charge-discharge rate characteristics of the C-CT / HS, EP-CT / HS, and EP-CT / HS / CL cathodes are compared under the same conditions. Figure 16 This is a table for comparing capacity characteristics.

[0046] Figure 17 For C-CT / HS, EP-CT / HS, and EP-CT / HS / CL cathodes (S-poly loading: 3 mg / cm³) 2 Analysis results of Nyquist plots.

[0047] Figure 18 For C-CT / HS, EP-CT / HS, EP-CT / HS / CL cathodes (S-poly loading: 3 mg / cm³) 2 The results of the cyclic test.

[0048] Reference Figure 14 , Figure 15 , Figure 16 , Figure 17 , Figure 18 According to the present invention, compared with carbon support (C-CT), the porous conductive structure EP-CT of the present invention has superior charge transport characteristics and reaction efficiency. Furthermore, the performance and stability of the electrode material of the present invention can be further improved by introducing a conductive capping layer (CL) onto the EP-CT structure.

[0049] Figure 19 shows the effect of increasing S-poly loading to 3 mg / cm³. 2 5mg / cm 2 8mg / cm 2 We will analyze the capacity and performance stability curves per unit area / mass of the EP-CT / HS / CL cathode. Detailed Implementation

[0050] This invention can be modified in many ways and has multiple embodiments. Specific embodiments are described in detail below with reference to the accompanying drawings. However, this is not intended to limit the invention to a particular implementation. It should be understood that all variations, equivalents, and substitutions included within the scope of the invention's concept and technology should be included in this invention. In describing this invention, detailed descriptions of relevant prior art will be omitted if they are deemed likely to obscure the essence of the invention.

[0051] In order to solve the above problems, the present invention prepares a porous conductive structure with excellent processability by performing simple electroplating on a fabric material as an insulator, and shows that it can be used in electrodes, catalysts, etc. Furthermore, it has been confirmed that when used as an electrode, it can be applied as an energy storage device for high-performance batteries.

[0052] In particular, this invention involves heat-treating the fabric material at a temperature of 600°C to 900°C. Through this heat treatment, the fabric material (cellulose, silk, polyacrylonitrile, Kevlar, etc.) with an sp2-bonded hexagonal structure can be carbonized while retaining its own high-porosity network structure. The heat-treated material exhibits excellent electrical conductivity due to its carbonization into an sp2-bonded hexagonal structure. Furthermore, during subsequent electroplating, the application of the metallic active substance to the support with such high porosity can be uniformly applied to the entire support surface without the problems that occur when plating directly onto the fabric material itself, or the problem of over-plating only the surface without reaching the interior.

[0053] Figure 1 This diagram illustrates the steps of a method for preparing a porous conductive structure (EP-CT) based on fabric material according to an embodiment of the present invention.

[0054] Reference Figure 1 An embodiment of the present invention describes a method for preparing a conductive structure based on fabric material. First, a carbon support is prepared by carbonizing the fabric material through heat treatment.

[0055] In one embodiment of the invention, the aforementioned heat treatment temperature is crucial in determining the surface impedance that makes subsequent electroplating possible. In this invention, a surface impedance suitable for electroplating is obtained at a temperature of 700°C (361 ohms / sq). Therefore, heat treatment at a temperature above 700°C is preferred. Typically, to improve the conductivity of the fabric material itself, the heat treatment temperature is increased to above 2000°C. In this invention, it is sufficient to ensure minimum conductivity for subsequent electroplating. Therefore, heat treatment at a temperature above 700°C is preferred, preferably at a temperature greater than or equal to 700°C and less than 2000°C, more preferably at a temperature between 700°C and 1500°C, and most preferably at a level between 700°C and 900°C.

[0056] Then, electroplating is performed on the aforementioned carbon support. In one embodiment of the invention, the electroplating is performed by nickel plating, especially while maintaining a high porosity while reducing the surface impedance to a level suitable for electroplating. This allows for the rapid acquisition of high conductivity by electroplating on a carbon support with a hexagonal structure having an sp2 structure, thus enabling the fabric-based porous conductive structure to be prepared. The conductive structure of the present invention has a high porosity (which indicates a high specific surface area and active area), thereby increasing the sulfur loading.

[0057] In one embodiment of the present invention, the conductive material is nickel (Ni), but conductive materials that can be electroplated, such as copper (Cu) and aluminum (Al), are also included in the scope of the present invention.

[0058] Then, a mixed slurry (HS) of sulfur polymer and a first carbon material modified with a first functional group (e.g., amine group) is loaded into the aforementioned porous conductive structure (EP-CT). That is, the present invention has the advantage of being able to directly load the following substances together in a conductive structure forming a porous structure without additional binders: 1) an NH2-carbon material (e.g., carbon nanotubes) that improves conductivity and provides bonding strength with the capping layer (CL), and 2) a sulfur substance. In one embodiment of the present invention, carbon nanotubes are used, but any organic material, graphene, etc., can be included within the scope of the present invention.

[0059] Then, a protective layer is formed by a second carbon material modified with a second functional group (e.g., carboxyl group) that can self-assemble in layers by bonding with the functional groups of the first carbon nanotubes described above through hydrogen bonding.

[0060] The lithium-sulfur battery cathode provided by the above method comprises: a carbon support having a network structure of woven material; a conductive metal material electroplated on the carbon support; a sulfur polymer loaded in the conductive metal material; a first carbon material modified by a first functional group bonded to the sulfur polymer; and a second carbon material bonded to the first carbon material to form a capping layer. A large amount of sulfur can be loaded without additional binders, resulting in excellent conductivity and reaction efficiency.

[0061] Figure 2 The diagram illustrates the preparation of the porous conductive current collector according to the above embodiments of the present invention and its use as the positive electrode of a lithium-sulfur battery, as well as a diagram illustrating their combination.

[0062] For more details, see [link to relevant documentation]. Figure 12 Through hydrogen bonds between the first and second functional groups, carbon nanotubes can be bonded layer by layer, which means that the electrode of the present invention can introduce the desired functional groups into the electrode support in the manner described above.

[0063] The preparation and determination methods are summarized below.

[0064] 1) Forming a conductive carbon support by heat-treating the fabric material.

[0065] 2) A porous conductive structure with excellent electrical conductivity is prepared by electroplating on a carbon support.

[0066] 3) The electrical properties of the electrodes were determined using a four-probe array.

[0067] 4) Sulphur polymers (S-poly) are synthesized by polymerizing sulfur into polymers.

[0068] 5) Use -NH2 modified MWCNT surface to prepare mixed slurry with S-poly.

[0069] 6) The mixed slurry is loaded into porous metals and elevator interiors by impregnation.

[0070] 7) Multilayer loading is achieved by utilizing interlayer self-assembly to form hydrogen bonds between NH2-MWCNT and COOH-MNWCNT.

[0071] 8) Analyze the energy storage characteristics of the prepared lithium-sulfur battery cathode by evaluating its electrochemical properties.

[0072] The present invention will now be described in more detail through more specific embodiments.

[0073] Example

[0074] Preparation of sulfur polymer (S-poly)

[0075] Sulfur powder (4.50 g, 17.6 mmol) was heated to 185 °C in an oil bath. 1,3-Diisopropenylbenzene (0.5 g, 3.16 mmol) was added to the green molten sulfur. The mixture was stirred for 10 minutes and then cooled to room temperature.

[0076] Preparation of COOH-MWCNT and NH2-MWCNT

[0077] COOH-MWCNTs were prepared by oxidizing pure multi-walled carbon nanotubes (MWCNTs) in a mixed H₂SO₄ / HNO₃ solution at 70 °C for 3 hours. Then, NH₂-MWCNTs were prepared by stirring the COOH-MWCNT suspension with ethylenediamine (8.0 mL) and 1-(3-dimethylaminopropyl)-3-ethylcarbonyldiamine methyl iodide (800 mg) for 6 hours. The suspension was purified for another 3 days (MWCO: 12000-14000) to remove impurities and residues.

[0078] Fabrication of porous conductive structures with electroplated Ni (EP-CT)

[0079] Electroplated porous conductive structures (EP-CTs) were prepared by carbonizing a fabric material (cotton) and then electroplating it. For this purpose, the fabric was first washed and dried. Then, it was heated to 700°C at a rate of 2°C per minute for 3 hours. After cooling to room temperature, it was immersed in a watt bath and electroplated using nickel as the negative electrode and the fabric as the positive electrode. The current density during electroplating was 216 mA / cm² over 20 minutes. 2 Then wash and dry at room temperature.

[0080] Conductivity coverage of EP-CT electrodes coated with slurry (EP-CT / HS / CL)

[0081] To load sulfur, 65% by weight of the aforementioned S-poly, 25% by weight of carbon black, and 10% by weight of the aforementioned NH2-MWCNT were mixed in N-methyl-2-pyrrolidone (NMP), and the mixture was ultrasonically treated for 1 hour under high output power. Then, the prepared porous conductive structure (EP-CT) was impregnated in the aforementioned sulfur slurry (HS) to load it (EP-CT / HS). In particular, the present invention has the advantage that the amount of sulfur loaded can be controlled by the viscosity of the aforementioned sulfur slurry, which can be controlled according to the amount of N-methyl-2-pyrrolidone in the solvent. Then, using a vacuum pump, the prepared COOH-MWCNT and NH2-MWCNT solutions were sequentially coated onto the sulfur-loaded EP-CT / HS to form a capping layer (EP-CT / HS / CL).

[0082] Experimental Example

[0083] Figure 3a The surface impedance data are based on the heat-treated carbon support.

[0084] Reference Figure 3a and Figure 3b It can be seen that a surface impedance of 361.2 Ω / sq is present at 700°C, which is suitable for electroplating. Therefore, it can be concluded that the support of the structure of the present invention can be prepared by heat treatment at a temperature above 700°C.

[0085] Figure 4a and Figure 4b The images shown are photographs of the electroplating apparatus used in this embodiment and the support as the plating time progresses, as well as photographs before and after plating.

[0086] Reference Figure 4a and Figure 4b It can be seen that through Figure 4a In an electroplating apparatus, nickel is plated onto a support to form a conductive structure. In particular, it is known that a raised structure forms on the surface over time.

[0087] Figure 5 The X-ray diffraction results are shown for a porous conductive structure and a commercially available porous nickel support according to an embodiment of the present invention. The commercially available porous nickel support is nickel foam (Goodfellow, Index number: 028-002-00-7, CAS number: 7440-02-0).

[0088] Reference Figure 5 In the case of nickel coating on the fabric-based support of the present invention, it is known that different crystallinity exists. That is, through... Figure 5 The results show that the conductive structure (EP-CT) produced by carbide-electroplation according to the present invention can also form high-quality nickel, just like existing commercially available porous nickel structures.

[0089] Figure 6 The results were obtained to determine the changes in the electrical properties of the carbon support over time.

[0090] Reference Figure 6 It can be seen that the impedance decreases with electroplating time. In particular, this linear impedance reduction is different from the phenomenon of over-plating only on the outer surface of the fabric material without coating the interior, that is, the phenomenon that the impedance does not decrease rapidly after the initial stage. The above results prove that the present invention can uniformly plate into the interior of the fabric material without over-plating.

[0091] Figure 7 and Figure 8 The images shown are scanning electron microscope (SEM) images and elemental distribution images of the conductive structure (EP-CT) of the present invention, and scanning electron microscope (SEM) images and elemental distribution images of the conductive structure with a non-carbonized, non-electroplated fabric material support.

[0092] Reference Figure 7 and Figure 8 It can be confirmed that the nickel distribution in the present invention is uniform, and in particular, it is known that the surface of the coated metal material includes a structure of nano-sized protuberants, resulting in uniform coating. On the other hand, it is known that without an electrolytic plating layer, the uniformity of the coated conductive material is significantly reduced, leading to problems such as agglomeration and pore blockage.

[0093] Figure 9 and Figure 10 The images shown are scanning electron microscope (SEM) images of the porous conductive structure (EP-CT) of the present invention and a commercially available porous nickel support.

[0094] Reference Figure 9 and Figure 10It can be seen that, compared with commercially available nickel supports, the porous conductive structure of the present invention has significantly higher porosity and active area.

[0095] Figure 11 The result of loading sulfur polymer (S-poly) into the porous conductive structure (EP-CT) of the present invention.

[0096] Reference Figure 11 Therefore, in the case of this invention, the sulfur polymer loading is 3 mg or more to 8 mg / cm³. 2 That is, it can be confirmed that when coating a mixed slurry containing S-poly (S-poly, NH2-MWCNT, carbon black) in the embodiment (EP-CT) of the present invention, based on the S-poly loading amount, a coating up to 3 mg / cm³ can be achieved without clogging the pores. 2 5mg / cm 2 8mg / cm 2 The large quantity demonstrates that the conductive structure prepared according to the present invention can load a larger amount of active material while maintaining the original pore and network structure of the initial fabric material.

[0097] Figure 12 A schematic diagram illustrating the method for preparing EP-CT / HS / CL by loading a carbon material modified by a second functional group and a carbon material modified by a first functional group onto EP-CT / HS to form a capping layer, and a diagram illustrating its binding mechanism.

[0098] Reference Figure 12 Carbon nanotubes can be multilayered through hydrogen bonding between the first and second functional groups. This capping layer, formed based on the bonding forces between functional groups, not only improves the conductivity of the EP-CT / HS electrode but also enhances its performance stability. This is because the electrode of the present invention can stably introduce the desired functional groups into the electrode support in the aforementioned manner.

[0099] Figure 13 For the EP-CT / HS / CL cathode (S-poly loading: 3 mg / cm³) forming a capping layer in EP-CT / HS, 2 The results of the cyclic voltammetry determination were obtained.

[0100] Reference Figure 13 With 0.03mVs -1 The speed scan cyclic voltammetry was used, with the voltage range being Li / Li+vs 1.7V to 2.8V. Observations showed that the cyclic voltammetry scan results under normal conditions should show two reduction peaks centered at 2.28V and 1.98V, because: (1) S-poly is reduced to shorter oligosulfide units and lithium polysulfides (Li2S). x(2) S-poly is converted into fully discharged organic sulfur-DIB products and insoluble lithium sulfide (Li2S2 and Li2S).

[0101] Conversely, oxidation peaks appear at 2.31V and 2.42V, because the short-chain organic sulfur-DIB is converted into long-chain S-poly upon full discharge.

[0102] Figure 14 EP-CT / HS / CL cathode (S-poly loading: 3 mg / cm³) 2 The results of the constant current charge / discharge (GCD) measurement.

[0103] Reference Figure 14 C-CT / HS with sulfur slurry loaded on an unplated carbon support, EP-CT / HS without a capping layer, and EP-CT / HS / CL with a capping layer showed two discharge plateaus, which is consistent with... Figure 13 The results were consistent with those obtained by the cyclic voltammetry method.

[0104] That is, in Figure 14 The amount of S-poly was fixed at 3 mg / cm³. 2 At that time, EP-CT / HS (secondary discharge plateau period: 1.9 mAh / cm³) 2 and ΔE: 165mV) and EP-CT / HS / CL (2.1mAh / cm) 2 and 156mV) showed a higher performance than C-CT / HS (1mAh / cm). 2 It also exhibits a much longer secondary discharge plateau period (210mV) and a smaller voltage difference (ΔE). This indicates that the porous conductive structure (EP-CT) of the present invention has higher point and reaction efficiency than the carbonized support (C-CT), and excellent interfacial reaction with active materials.

[0105] Figure 15 For 3mg / cm 2 The curves comparing the speed characteristics of lithium-sulfur batteries under different loading capacities are shown. Figure 16 This is a table for comparing capacity characteristics.

[0106] Reference Figures 15 to 16 It can be seen that when the porous conductive structure (EP-CT) of the present invention is used as an electrode and introduced into the capping layer in a layered self-assembly manner, it exhibits rapid interfacial reaction, outstanding speed characteristics, and high capacity. Specifically, it can be seen that with a loading of 3 mg / cm³ of S-poly as the active material...2 Based on the baseline, without the coating layer, the performance value of EP-CT / HS (the present invention) is higher than that of C-CT / HS (comparative example). This indicates that, compared to C-CT, EP-CT can improve performance due to the rapid redox reaction of sulfur during charge and discharge. Furthermore, Figure 15 This demonstrates that, with increasing charge rate (C-rate), EP-CT can potentially achieve faster charge and discharge due to its higher performance compared to C-CT. Figure 16 The differences between them can be known quantitatively, especially that the charge and discharge characteristics improve with the formation of the capping layer.

[0107] Figure 17 The results are the Nyquist plot analysis results for each electrode.

[0108] Reference Figure 17 The results show that the charge transfer impedance (Rct) of the EP-CT / HS cathode of the present invention is lower than that of C-CT / HS, indicating that EP-CT (123Ω) has faster charge transfer characteristics than C-CT (164Ω). Furthermore, the EP-CT / HS / CL cathode with the capping layer exhibits an even lower charge transfer impedance (81Ω), demonstrating that the lithium-sulfur battery cathode of the present invention exhibits rapid redox kinetics by introducing a conductive capping layer onto the EP-CT structure.

[0109] Figure 18 Cyclic test results are provided to demonstrate the extremely high cyclic stability of the electrodes of the present invention.

[0110] Reference Figure 18 It can be seen that the electrode with the conductive capping layer of the present invention has higher stability and maintains a high areal capacity.

[0111] Figure 19 shows the concentration at 3 mg / cm³. 2 5mg / cm 2 8mg / cm 2 The graph shows the performance curves of the lithium-sulfur battery cathode under the specified loading capacity.

[0112] Referring to Figure 19, it can be seen that when the conductive structure of the present invention is used as an electrode, a high energy capacity per unit area / mass can be achieved.

[0113] As shown in Figure 19, by increasing the loading of S-poly to 8 mg / cm³, 2 To achieve excellent performance per unit area and per unit mass, the results ultimately demonstrate that EP-CT, as a metal, has excellent charge transfer characteristics, exhibiting high loading capacity and thus excellent performance per unit area due to its porous structure.

[0114] That is, the electrode structure of the present invention can not only be used in energy storage devices, but also immobilize biologically active substances (such as enzymes or probes) based on its own conductivity and high loading capacity. In this case, liquid samples can be contacted by a large amount of absorption by the porous support. Therefore, compared with biosensors using substrate structures such as glass, the present invention can develop sensor electrodes with high sensitivity even with small amounts of samples.

[0115] Furthermore, the present invention uses an additional capping layer to improve the performance efficiency and stability of the positive electrode, which means that any functional group capable of binding with sensor probe material can be introduced into a conductive support with metallic properties.

[0116] The conductive structure of the present invention described above can be used not only in the electrodes of energy storage devices, but also in conductive materials that require high specific surface area and high porosity, such as catalysts and sensors, all of which are included within the scope of the present invention.

[0117] Industrial availability

[0118] This invention relates to electrode devices, which are considered to have industrial applicability.

Claims

1. A method for preparing a lithium-sulfur battery cathode using fabric materials, wherein, The method includes: The step of preparing a conductive support by carbonizing the fabric material through heat treatment at 600°C to 900°C; The step of electroplating a conductive metal material onto the aforementioned conductive support; In the step of loading a slurry onto an electroplated conductive support, the slurry comprises a sulfur polymer and a first carbon material modified by a first functional group capable of hydrogen bonding with the sulfur polymer; and In the step of loading a second carbon material onto the conductive support, the second carbon material is modified with a second functional group capable of hydrogen bonding with the first functional group, thereby forming a capping layer by layered self-assembly of the first carbon material and the second carbon material.

2. The method for preparing a lithium-sulfur battery cathode using fabric materials according to claim 1, wherein, The first carbon material and the second carbon material are carbon nanotubes, the first functional group is an amino group, and the second functional group is a carboxyl group.

3. The method for preparing a lithium-sulfur battery cathode using fabric materials according to claim 1, wherein, The conductive support prepared by the heat treatment retains the network structure of the fabric material as is.

4. The method for preparing a lithium-sulfur battery cathode using fabric materials according to claim 1, wherein, The conductive metallic material comprises one or more selected from the group consisting of nickel, copper, and aluminum.

5. The method for preparing a lithium-sulfur battery cathode using fabric materials according to claim 1, wherein, The fabric material is a fabric containing carbon atoms in the main chain.

6. A lithium-sulfur battery cathode, comprising: A conductive support having a network structure of woven material; A conductive metallic material is coated onto the conductive support. Sulfur polymers are loaded into the conductive metal material; as well as A capping layer is formed by layered self-assembly of a first carbon material and a second carbon material, wherein the first carbon material is modified with a first functional group that binds to the sulfur polymer, and the second carbon material is modified with a second functional group that can bind to the first functional group via hydrogen bonds.

7. The lithium-sulfur battery cathode according to claim 6, wherein, The lithium-sulfur battery cathode is prepared by any one of claims 1 to 5.

8. The lithium-sulfur battery cathode according to claim 6, wherein, The first carbon material and the second carbon material are carbon nanotubes, the first functional group is an amino group, and the second functional group is a carboxyl group.

9. The lithium-sulfur battery cathode according to claim 6, wherein, The conductive metallic material comprises one or more selected from the group consisting of nickel, copper, and aluminum.

10. A lithium-sulfur battery, characterized in that, It includes the lithium-sulfur battery cathode as described in claim 6.

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