Nanostructure for lithium-sulfur battery, method for manufacturing the same, interlayer for lithium-sulfur battery and lithium-sulfur battery comprising same

Abstract

The present invention relates to a nanostructure comprising porous carbon nanofibers and a two-dimensional material, a method for manufacturing the same, an intermediate layer for a lithium-sulfur battery comprising the same, and a lithium-sulfur battery.

Description

Technology Field

[0001] The present invention relates to a nanostructure comprising porous carbon nanofibers and a two-dimensional material, a method for manufacturing the same, an intermediate layer for a lithium-sulfur battery comprising the same, and a lithium-sulfur battery. Background Technology

[0002] Recently, lithium-sulfur batteries (LSBs) have been attracting attention as next-generation batteries because they utilize sulfur as a raw material—which is abundant in nature, eco-friendly, and cost-effective—and the low density of the sulfur element itself allows for lightweight design and the storage of large amounts of energy. The theoretical capacity of lithium-sulfur batteries is 1,675 mAh / g, which is higher than the theoretical capacity of lithium-ion batteries (374 mAh / g). Furthermore, sulfur, which is primarily used as the cathode material for lithium-sulfur batteries, is inexpensive due to its high reserves. In addition to this high theoretical capacity, sulfur is much lighter than metals, which can be a significant advantage when applied to systems such as electric vehicles and drones. Moreover, while the volumetric energy density of lithium-sulfur batteries is 700 Wh / L, similar to that of lithium-ion batteries, the gravimetric energy density can be at least twice as high, ranging from 400 to 600 Wh / kg, offering a significant advantage for applications in systems requiring miniaturization and low weight.

[0003] However, despite the various advantages described earlier, lithium-sulfur batteries face several challenges that must be overcome for commercialization. First, low conductivity is an issue because sulfur is used as the cathode active material. Currently, conductive additives are introduced to address this, but this leads to an increase in the overall weight of the battery. Additionally, the issue of the shuttle effect of lithium polysulfides must be resolved. Lithium polysulfides dissolve in the electrolyte and repeatedly move between the anode and cathode within the battery, causing leaching. When leaching occurs, the irreversibility of sulfur continuously increases with repeated charging and discharging cycles, resulting in the loss of active material within the cathode and a decrease in battery safety and lifespan.

[0004] Currently, to address these issues, research is being conducted on the development of various carbon hosts, modifications to electrode structures, and electrolyte optimization. Among these, studies are underway to improve electrode characteristics by modifying the separator surface through the introduction of interlayers or by adding additional components. However, in the case of introducing interlayers, there are still issues such as a decrease in the overall energy density of the battery due to the thickness and weight of the interlayer, and increased resistance caused by the physical presence of the interlayer.

[0005] Therefore, research is currently underway to improve the characteristics of lithium-sulfur batteries, as the introduction of an intermediate layer enables excellent conductivity and allows for the suppression of the shuttle effect through the promotion of redox reactions. The problem to be solved

[0006] The present invention was created to solve the various problems of the prior art as described above, and aims to provide a nanostructure capable of preventing the shuttle effect of a lithium-sulfur battery and improving electrical conductivity and ion diffusion rate, a method for manufacturing the same, an intermediate layer for a lithium-sulfur battery including the same, and a lithium-sulfur battery. means of solving the problem

[0007] To achieve the above objectives, a method for manufacturing a nanostructure according to one embodiment of the present invention may include the steps of manufacturing a nanofiber web, heat-treating the nanofiber web to obtain porous carbon nanofibers (PCNF), and coating a two-dimensional material on or on the surface of the porous carbon nanofibers.

[0008] A nanostructure according to one embodiment of the present invention comprises porous carbon nanofibers (PCNF) and a two-dimensional material, and the two-dimensional material may be dispersed within or on the surface of the porous carbon nanofibers (PCNF).

[0009] An interlayer for a lithium-sulfur battery according to one embodiment of the present invention may include a nanostructure according to various embodiments of the present invention.

[0010] A lithium-sulfur battery according to one embodiment of the present invention may include an interlayer for a lithium-sulfur battery according to various embodiments of the present invention. Effects of the invention

[0011] The nanostructure according to the present invention includes carbon nanofibers with a porous structure, so that the specific surface area can be increased and the active region can be increased.

[0012] Accordingly, this can be incorporated into lithium-sulfur batteries to improve the problem of low conductivity.

[0013] In addition, the nanostructure according to the present invention includes not only porous carbon nanofibers but also two-dimensional materials, which can improve the diffusion rate of ions within the battery and have excellent electrical conductivity.

[0014] Accordingly, the oxidation-reduction reaction can be promoted to suppress the shuttle effect of the lithium-sulfur battery.

[0015] In addition, when included in a lithium-sulfur battery, it can improve the capacity and stability of the battery. Brief explanation of the drawing

[0016] Figure 1(a) is an SEM image of the nanostructure of Example 1, (b) is an SEM image of Example 2, and (c) is an SEM image of Example 3. Figures 2(a) and (b) are TEM images of Example 2. Figure 3 is an EDS mapping image of Example 2. Figure 4 is a graph showing the rate capability characteristics of Examples 4 to 6. Figure 5(a) is a graph showing the Galvanostatic Charge-Discharge (GCD) characteristics of Examples 4 to 6 at 0.2C, and (b) is a graph showing the voltage difference of Examples 4 to 6. Figure 6 is a graph showing the rate capability characteristics of Comparative Example 1, Comparative Example 2, and Example 5. Figure 7(a) is a graph showing the Galvanostatic Charge-Discharge (GCD) characteristics of Comparative Example 1, Comparative Example 2, and Example 5 at 0.2C, and (b) is a graph showing the voltage difference of Comparative Example 1, Comparative Example 2, and Example 5. Figure 8 (a) is a graph showing the cycle characteristics at 0.1C, and (b) is a graph showing the cycle characteristics at 1C. Specific details for implementing the invention

[0017] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0018] In this application, terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0019] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the existence 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.

[0021] The method for manufacturing a nanostructure of the present invention may include the steps of manufacturing a nanofiber web, heat-treating the nanofiber web to obtain porous carbon nanofibers (PCNF), and coating a two-dimensional material on or on the surface of the porous carbon nanofibers.

[0023] The step of manufacturing the nanofiber web described above can be carried out by electrospinning a solution containing polyacrylonitrile (PAN) and polystyrene (PS). The electrospinning solution for performing the electrospinning process can be prepared by dispersing the polyacrylonitrile (PAN) and polystyrene (PS) in an organic solvent and stirring.

[0024] In one embodiment of the present invention, the polyacrylonitrile (PAN) and polystyrene (PS) may be dispersed in an organic solvent in a weight ratio of 1:2 to 3:4. Preferably, they may be dispersed in an organic solvent in a weight ratio of 2:3.

[0025] After that, it can be mixed by stirring at 60 to 70 ℃ for 10 to 14 hours. Preferably, it can be mixed by stirring at 65 ℃ for 12 hours.

[0026] As described above, when polyacrylonitrile (PAN) is included in the electrospinning solution, a carbon fiber shape can be formed through the heat treatment step described later. That is, polyacrylonitrile (PAN) can serve as a carbon fiber precursor, but is not limited thereto and any material capable of becoming carbon fiber after heat treatment can be used.

[0027] As described above, when polystyrene (PS) is included in the electrospinning solution, a porous structure can be formed through the heat treatment step described later. In one embodiment of the present invention, the polystyrene (PS) may be in the form of nanobeads and may have a diameter of 40 to 60 nm. Preferably, it may be 50 nm.

[0028] This polystyrene (PS) can be removed after heat treatment, thereby providing a porous structure to the nanostructure of the present invention.

[0029] Meanwhile, the above organic solvent may be dimethylformamide (N,N-dimethylformamide, DMF), but is not limited thereto.

[0031] Next, the step of heat-treating the nanofiber web of the present invention to obtain porous carbon nanofibers (PCNF) can be performed at 700 to 900°C. Polyacrylonitrile (PAN) included in the nanofiber web can be carbonized at 700 to 900°C to form carbon nanofibers. Preferably, it can be carbonized at 800°C to form carbon nanofibers.

[0032] At this time, the polystyrene (PS) included in the nanofiber web can be removed to provide a porous structure.

[0033] According to one embodiment of the present invention, a step of stabilizing at 240 to 260°C before heat treatment at 700 to 900°C may be further included. At this time, the nanofiber web may be oxidized.

[0035] The porous carbon nanofiber (PCNF) obtained in this way may have a thickness of 12 to 20 μm. Preferably, it may be 16 μm. If the porous carbon nanofiber does not meet the thickness range described above, damage due to the thin thickness may occur during the vacuum filtration process described later. Therefore, the above range may be preferred.

[0036] In addition, the porous carbon nanofiber may include pores of various sizes. In one example, it may include both mesopores of 2 to 4 nm in size and micropores of 0.6 to 0.7 nm in size.

[0037] The nanostructure of the present invention includes the porous carbon nanofibers, which can increase the specific surface area and the active region. This enables rapid charge transport during charging and discharging of a battery containing the nanostructure of the present invention, thereby contributing to the storage of more charge.

[0039] Next, a step of coating a two-dimensional material on or on the surface of the porous carbon nanofiber of the present invention may be performed. At this time, the coating step may be performed through vacuum filtration.

[0040] For the above vacuum filtration, the method for manufacturing a nanostructure of the present invention may further include the step of preparing a solution containing the two-dimensional material.

[0041] The above two-dimensional material may be any one selected from the group consisting of MXene, graphene, MoS2, and boron nitride (BN). Preferably, it may be MXene, but the examples are not limited thereto, and various other two-dimensional materials may be used.

[0042] Specifically, the above MXene is Ti3C2T x MXene, Ti2CT x MXene, V2CT x MXene, Mo2CT x MXene, TiVCT x MXene and Mo2TiC2T x It may be any one selected from the group consisting of MXene, preferably V2CT XIt is an MXene, and its lateral size may be 0.7 to 1.1 μm. (T x is -O, -OH, or -F.

[0043] MXene is M n+1 AX n An inorganic compound M formed by removing the A layer from MAX, which exists as a stacked structure of an internal A layer and M2X, M3X, and M4X layers forming the molecular formula n+1 X n It has the molecular formula (n = 1, 2, 3). Here, M is a transition metal element, such as Ti (titanium), V (vanadium), Mo (molybdenum), etc., but is not limited thereto. Here, A is a group 13 or 14 element, such as Al (aluminum) or Si (silicon), etc., but is not limited thereto. Here, X can be C (carbon), N (nitrogen), etc., but is not limited thereto.

[0044] In the step of removing the above A layer, the MXene from which the A layer has been removed internally through the etching process has functional groups of -O, -OH, and -F generated during the etching process on its surface, and M n+1 X n T x It is expressed as. At this time, T x It can be a surface functional group such as -OH, -O, -F, but is not limited to these.

[0045] MXene is hydrophilic due to various functional groups on its surface and can possess excellent electrical conductivity. In particular, it can improve electron transfer capability to increase high-speed performance, which can lead to an increase in capacitance retention rate.

[0047] In the present invention, the porous carbon nanofiber can be placed in the filter portion of a vacuum filtration device, and then a solution containing the two-dimensional material can be introduced to perform vacuum filtration.

[0048] Through the above vacuum filtration, the two-dimensional material can be uniformly dispersed within or on the surface of the porous carbon nanofiber.

[0049] The nanostructure of the present invention includes a two-dimensional material as described above, which can improve the diffusion rate of ions within the battery and can have excellent electrical conductivity. Accordingly, it can promote an oxidation-reduction reaction and suppress the shuttle effect of a lithium-sulfur battery.

[0051] The nanostructures manufactured through the above method may include porous carbon nanofibers (PCNF) and two-dimensional materials.

[0052] The two-dimensional material included in the nanostructure of the present invention may be dispersed within or on the surface of the porous carbon nanofiber (PCNF).

[0053] The porous carbon nanofibers and two-dimensional materials mentioned above are the same as those previously described, so a detailed explanation thereof will be omitted.

[0054] A nanostructure according to one embodiment of the present invention may contain 10 to 40 weight percent of the two-dimensional material.

[0056] The interlayer for a lithium-sulfur battery of the present invention may include a nanostructure according to the various embodiments described above.

[0057] In addition, the lithium-sulfur battery of the present invention may include an interlayer for the lithium-sulfur battery, a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode.

[0058] The interlayer of the present invention may be disposed between the anode and the separator. When the interlayer is disposed between the anode and the separator, it can effectively suppress the shuttle effect by capturing lithium polysulfide flowing out from the anode.

[0059] Accordingly, the lithium-sulfur battery of the present invention can improve electrochemical performance by placing an intermediate layer between the positive electrode and the separator to form a conductive path that facilitates charge transfer, and by increasing ion-accessible sites within the structure and achieving structural stability. In addition, due to the large specific surface area of ​​the intermediate layer, it possesses excellent physical adsorption characteristics, thereby capturing lithium polysulfides that migrate during repeated charging and discharging, which can improve the utilization rate of sulfur.

[0060] The present invention will be explained in more detail below through examples. However, the following examples and experimental examples are intended only to explain the present invention more specifically, and the scope of the present invention is not limited by the following examples and experimental examples.

[0062] Example 1

[0063] V2CT with 2D material X To use MXene, V2AlC2MAX phase precursor powder was prepared. Subsequently, a 48% HF solution was placed in a Teflon container, and the V2AlC2MAX phase powder was slowly added. The etching process was then carried out by stirring at 35°C for 96 hours. Afterward, distilled water (DI water) was added to the reaction mixture, and the mixture was washed using a centrifuge; this process was repeated until all Al was removed. Following washing, a Tetrabutylammonium hydroxide (TBAOH) solution was added, and the stripping process was carried out by stirring at room temperature for 24 hours. Subsequently, the reaction mixture was centrifuged at 3000 rpm for 10 minutes to remove the TBAOH solution, and centrifugation was repeated using distilled water to remove V2CT X A solution containing MXene was prepared.

[0064] To fabricate porous carbon nanofibers (PCNF), structures were prepared using an electrospinning process. First, to prepare the solution for electrospinning, 4.68 wt% PAN and 7.02 wt% PS were added to 88.31 wt% DMF, and the mixture was stirred at 65 °C for 12 hours. At this time, PS with a diameter of approximately 50 nm was used to form a porous structure. After stirring, the mixed solution was injected into a plastic syringe equipped with a 23-gauge stainless steel needle, and electrospinning was performed under conditions of a voltage of 15.0 kV, a solution feed rate of 1 mL / h, and a collection distance of 15 cm. The fibers obtained by electrospinning were stabilized by oxidizing in air at 260°C for 2 hours at a heating rate of 2°C / min, and then carbonized in an argon atmosphere at 800°C for 1 hour at a heating rate of 5°C / min. The thickness of the porous carbon nanofibers obtained in this way was measured to be 16 μm.

[0065] The final nanostructure is the previously fabricated porous carbon nanofiber (PCNF) and V2CT X It was prepared using a vacuum filtration process with an MXene solution. First, porous carbon nanofibers were prepared to fit the holder diameter (Ψ 36 mm) of the vacuum filtration equipment and placed in the filter section. Subsequently, V2CT X The MXene solution was introduced onto porous carbon nanofibers, and vacuum filtration was performed. The filtered nanostructures were vacuum dried at 60°C for 12 hours. Meanwhile, the V2CT introduced to perform vacuum filtration X The amount of MXene, i.e., V2CT X The loading amount of MXene is 0.182 mg / cm² 2It was measured as such. In addition, the weight of the nanostructure produced at this time was 2.69 mg, and the weight of MXene was 0.39 mg.

[0066] The final nanostructure produced in this way was named LMX / PCNF.

[0068] Example 2

[0069] V2CT introduced to perform vacuum filtration X Nanostructures were prepared using the same method as in Example 1, except for the amount of MXene. In this example, V2CT X The loading amount of MXene is 0.374 mg / cm² 2 It was, and the weight of the nanostructure produced at this time was 3.10 mg, and the weight of MXene was 0.8 mg.

[0070] The final nanostructure produced in this way was named MMX / PCNF.

[0072] Example 3

[0073] V2CT introduced to perform vacuum filtration X Nanostructures were prepared using the same method as in Example 1, except for the amount of MXene. In this example, V2CT X The loading amount of MXene is 0.594 mg / cm² 2 The weight of the nanostructure produced at that time was 3.57 mg, and the weight of MXene was 1.27 mg.

[0074] The final nanostructure produced in this way was named HMX / PCNF.

[0076] Example 4

[0077] A lithium-sulfur battery coin cell was manufactured. The nanostructure according to Example 1 was used as an interlayer between the anode and the separator, lithium metal was used as the negative electrode, and an S / CNT electrode (loading amount 1.4 mg / cm²) was used as the positive electrode. 2A polypropylene (PP) membrane, Celgard 2400, was used as the separator, and a coin cell was fabricated in an Ar atmosphere using a mixture of 1.0 M LiTFSI and 2 wt% LiNO3 in a DOL / DME solution (1:1, v / v) as the electrolyte.

[0079] Example 5

[0080] A coin cell was manufactured in the same manner as in Example 4, except that the nanostructure of Example 2 was used as the interlayer between the anode and the separator.

[0082] Example 6

[0083] A coin cell was manufactured in the same manner as in Example 4, except that the nanostructure of Example 3 was used as the interlayer between the anode and the separator.

[0085] Comparative Example 1

[0086] A coin cell was manufactured in the same manner as in Example 4, except that it did not include an interlayer.

[0088] Comparative Example 2

[0089] A coin cell was prepared in the same manner as in Example 4, except that porous carbon nanofiber (PCNF) not containing two-dimensional material was used as the interlayer.

[0091] Experimental Example 1

[0092] Morphological observation

[0093] In this experiment, the morphology of the nanostructures of Examples 1 to 3 was observed. SEM images of Examples 1 to 3 are shown in Figure 1.

[0094] Figure 1 (a) is an SEM image of the nanostructure of Example 1, (b) is an SEM image of Example 2, and (c) is an SEM image of Example 3.

[0095] Referring to Fig. 1, V2CT on the surface of the porous carbon nanofiber (PCNF) of the nanostructure x It can be commonly confirmed that MXene is distributed. Meanwhile, in the case of Example 1, V2CT x Since it can be confirmed that the MXene is relatively less evenly dispersed, it can be anticipated that forming the nanostructure according to the present invention may be difficult when containing less two-dimensional material than the nanostructure of Example 1. Furthermore, in the case of Example 3, V2CT compared to Example 2 x It can be seen that the MXene is in excess and relatively covers the pores. Through this, it can be anticipated that if a two-dimensional material is included more than the nanostructure of Example 3, it may be difficult to secure a porous structure like that of the present invention.

[0097] Next, the structure of the nanostructure of Example 2 among Examples 1 to 3 was observed in more detail. This is shown in FIGS. 2 and FIGS. 3. FIGS. 2 (a) and (b) are TEM images of Example 2, and FIGS. 3 is an EDS mapping image of Example 2.

[0098] Referring to Fig. 2(a), the dark areas represent strands of porous carbon nanofibers, and looking at the magnified image in Fig. 2(b), the two-dimensional material V2CT on the surface of the carbon fibers x You can see the shape wrapped by MXene.

[0099] Referring to Figure 3, the distribution of elements corresponding to C, N, O, and V can be identified, and it can be seen that V is formed on the fiber surface and evenly distributed with fiber columns mainly composed of C and N elements as the main axis.

[0101] Experimental Example 2

[0102] Evaluation of electrochemical properties

[0103] In this experiment, the electrochemical characteristics of the lithium-sulfur batteries of Examples 4 to 6 were evaluated. These are shown in Figures 4 and 5. Figure 4 shows the rate capability characteristics of Examples 4 to 6, Figure 5 (a) shows the Galvanostatic Charge-Discharge (GCD) characteristics of Examples 4 to 6 at 0.2 C, and Figure 5 (b) shows the voltage difference of Examples 4 to 6.

[0104] Referring to Figures 4 and 5, it can be confirmed that the capacity is superior in the order of Example 5, Example 4, and Example 6. In the case of Example 5, it can be seen that the capacity increases at each current density and the voltage difference is also the lowest. This indicates an appropriate V2CT x This can be understood as a result of the excellent charge / discharge rate due to the amount of MXene. In the case of Example 4, V2CT, which plays a role in enhancing battery performance by promoting oxidation-reduction, x It was confirmed that the characteristics were superior to the battery of Example 5, as the amount of MXene was lower than in Example 5. In addition, in the case of Example 6, V2CT x The amount of MXene was relatively high, which reduced the pores between the fibers and exhibited excellent characteristics second only to the battery of Example 4.

[0106] Experimental Example 3

[0107] Evaluation of electrochemical properties

[0108] In this experiment, the electrochemical characteristics of the battery of Example 5, which was measured to have excellent electrochemical characteristics in Experimental Example 2, were compared with those of the batteries of Comparative Example 1 and Comparative Example 2. This is illustrated in Figures 6 to 8. Figure 6 shows the rate capability characteristics of Comparative Example 1, Comparative Example 2, and Example 5. Figure 7 (a) shows the Galvanostatic Charge-Discharge (GCD) characteristics of Comparative Example 1, Comparative Example 2, and Example 5 at 0.2 C, and (b) shows the voltage difference of Comparative Example 1, Comparative Example 2, and Example 5. Figure 8 (a) shows the cycle characteristics at 0.1 C, and (b) shows the cycle characteristics at 1 C.

[0109] Meanwhile, in FIGS. 6 to 8, the battery of Example 5 is represented as V2C MXene / PCNF. Also, the battery of Comparative Example 1 is represented as Bare in the figure, and the battery of Comparative Example 2 is represented as PCNF in the figure.

[0110] Referring to Figure 6, as the current density increases, the battery of Example 5 maintains a capacity of 1319.4 mAh / g and 760.4 mAh / g at 0.1 C and 3.0 C, respectively, and when the current density is changed back to 0.1 C, it has a capacity of 1208.7 mAh / g (91.6% of the initial value), confirming that it has an excellent recovery rate.

[0111] On the other hand, the battery of Comparative Example 2 maintains a capacity of 1177.7 mAh / g and 680.9 mAh / g at 0.1 C and 3.0 C, respectively, and maintains a capacity of 1058.7 mAh / g (89.8% of the initial value) when changed to 0.1 C, showing lower capacity and recovery rate than the battery of Example 5.

[0112] In addition, in the case of Comparative Example 1, it was found that it maintained low capacities of 878.3 mAh / g and 510.4 mAh / g at 0.1 C and 3.0 C, respectively, and showed the lowest capacity and recovery rate of 702.1 mAh / g (79.9% of the initial value) when the current density was changed back to 0.1 C.

[0113] Through this, the V2CT included in Example 5 x It can be seen that the composition of MXene and porous carbon nanofibers (PCNF) effectively promotes the redox reaction of sulfur, resulting in excellent electrochemical properties.

[0115] Referring to Fig. 7, it can be seen that the voltage difference of the battery in Example 5 is lower than that of the batteries in Comparative Examples 1 and 2. This indicates that the battery in Example 5 is V2CT x This is because rapid charging and discharging was possible due to the composition of MXene and porous carbon nanofibers (PCNF), and the effect of Example 5, previously confirmed in Figure 6, was confirmed once again.

[0117] Referring to Fig. 8(a), it can be seen that the battery of Example 5 maintained a high capacity of 1,076.81 mAh / g even after 80 cycles at 0.1 C. In contrast, the batteries of Comparative Example 2 and Comparative Example 1 showed much lower capacities of 842.70 and 511.41 mAh / g, respectively, after 80 cycles.

[0118] In addition, referring to Fig. 8(b), it was confirmed that the battery of Example 5 maintained a discharge capacity of 762.73 mAh / g even after 300 cycles at 1.0 C, exhibiting a high capacity retention rate of 76.9% and a low capacity decay rate of 0.0771%. On the other hand, it was confirmed that the electrochemical characteristics of the battery of Comparative Example 2 deteriorated, showing a capacity retention rate of 67.6% and a capacity decay rate of 0.1081%.

[0119] These results are similar to V2CT as in Example 5.x It is shown that introducing MXene and porous carbon nanofibers (PCNF) as an interlayer can effectively suppress the shuttle effect of lithium polysulfide and ensure excellent cycle stability and high reversible capacity.

[0120] Furthermore, it can be confirmed that the battery of Example 5 maintains consistent Coulombic Efficiency during repeated charging and discharging. This is an indicator showing how efficiently the battery stores and releases charge, and it can be seen that the battery of Example 5 recovers almost all of the charged charge during the discharge process through a Coulombic Efficiency close to 100%. Through this, V2CT x It was confirmed that the efficiency and stability of a lithium-sulfur battery can be improved by introducing MXene and porous carbon nanofibers (PCNF) as an interlayer.

[0122] The present invention has been described above with reference to its preferred embodiments. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of the claims should be interpreted as being included in the invention.

Claims

Claim 1 A method for manufacturing a nanostructure comprising: a step of manufacturing a nanofiber web; a step of heat-treating the nanofiber web to obtain porous carbon nanofibers (PCNF); and a step of coating a two-dimensional material on or on the surface of the porous carbon nanofibers, wherein the step of coating a two-dimensional material on or on the surface of the porous carbon nanofibers is characterized in that, after obtaining the porous carbon nanofibers (PCNF), the method is carried out through a vacuum filtration process using a solution containing the two-dimensional material. Claim 2 A method for manufacturing a nanostructure according to claim 1, wherein the step of manufacturing the nanofiber web comprises electrospinning a solution containing polyacrylonitrile (PAN) and polystyrene (PS). Claim 3 A method for manufacturing a nanostructure according to claim 1, wherein the step of heat-treating the nanofiber web to obtain porous carbon nanofibers (PCNF) is characterized by heat-treating at 700 to 900°C. Claim 4 A method for manufacturing a nanostructure according to claim 1, characterized in that the porous carbon nanofiber (PCNF) has a thickness of 12 to 20 μm. Claim 5 delete Claim 6 In claim 1, the two-dimensional material is Ti3C2T x MXene, Ti2CT x MXene, V2CT x MXene, Mo2CT x MXene, TiVCT x MXene and Mo2TiC2T x A method for manufacturing a nanostructure characterized by being one selected from the group consisting of MXenes. (T x is -O, -OH, or -F. Claim 7 In claim 1, the two-dimensional material is V2CT x It is MXene, and the above V2CT x A method for manufacturing a nanostructure characterized by the MXene having a lateral size of 0.7 to 1.1 μm. (T x is -O, -OH, or -F. Claim 8 A nanostructure manufactured by the method according to claim 1, wherein the nanostructure comprises porous carbon nanofibers (PCNF) and a two-dimensional material, and the two-dimensional material is dispersed within or on the surface of the porous carbon nanofibers (PCNF). Claim 9 In claim 8, the two-dimensional material is Ti3C2T x MXene, Ti2CT x MXene, V2CT x MXene, Mo2CT x MXene, TiVCT x MXene and Mo2TiC2T x A nanostructure characterized by being any one selected from the group consisting of MXenes. (T x is -O, -OH, or -F. Claim 10 In claim 8, the two-dimensional material is V2CT x A nanostructure characterized by being an MXene. (T x is -O, -OH, or -F. Claim 11 In claim 8, the nanostructure is characterized by comprising 10 to 40 weight percent of the two-dimensional material. Claim 12 A lithium-sulfur battery comprising: an interlayer for a lithium-sulfur battery including a nanostructure according to any one of claims 8 to 11; a positive electrode; a negative electrode; an electrolyte; and a separator disposed between the positive electrode and the negative electrode, wherein the interlayer for a lithium-sulfur battery is disposed between the positive electrode and the separator. Claim 13 delete Claim 14 delete

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