A TiN-NbC nanofiber membrane, its preparation method and application, and lithium-sulfur batteries.

Abstract

This invention provides a TiN-NbC nanofiber membrane, its preparation method, and its applications in lithium-sulfur batteries, relating to the field of secondary battery technology. The preparation method of the TiN-NbC nanofiber membrane provided by this invention includes the following steps: mixing a polymer, a titanium source, a niobium source, and an organic solvent to obtain a spinning solution; electrospinning the spinning solution on a substrate surface to obtain a composite fiber precursor on the substrate surface; and carbonizing the composite fiber precursor to obtain the TiN-NbC nanofiber membrane on the substrate surface; wherein the polymer includes polyacrylonitrile and / or polyvinylpyrrolidone. This invention uses electrospinning and a high-temperature solid-state method to synthesize the TiN-NbC membrane, resulting in a simple preparation method; furthermore, this invention contains no ionic impurities other than titanium and niobium metal ions, and the polymer is completely converted to carbon at high temperatures, without introducing impurity ions.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a TiN-NbC nanofiber membrane, its preparation method and application, and lithium-sulfur batteries. Background Technology

[0002] With the ever-increasing global energy demand, the research and exploration of high-energy-density secondary batteries has become a hot topic. Among numerous candidate batteries, lithium-sulfur batteries (LSBs) stand out due to their high theoretical energy density (2600 Wh / kg). -1 ) and theoretical specific capacity (1675mAh·g) -1 Lithium-ion batteries (LSBs) have garnered significant attention due to their relatively low cost. However, their application prospects remain uncertain due to several factors, including low sulfur utilization, poor cycle stability, significant sulfur volume expansion during the reaction, and low conductivity of sulfur and its discharge products (Li₂S₂ / Li₂S) caused by the shuttle effect of soluble polysulfides (LiPSs). The shuttle effect not only leads to the loss of cathode active material but also accelerates the corrosion and passivation of the lithium anode, resulting in capacity decay. Furthermore, lithium metal anodes suffer from lithium dendrite growth, large volume changes, and poor performance during cycling. Therefore, it is necessary to develop a material that mitigates lithium dendrite growth. In summary, the challenge in achieving high-performance lithium batteries lies in suppressing the shuttle effect and lithium dendrite growth.

[0003] In existing technologies, physical blocking is usually used to suppress the shuttle effect of polysulfides. Physical blocking involves directly applying a freestanding carbon film to the positive electrode side interlayer of an LSB battery, which can accommodate sulfur and polysulfides and limit the diffusion of polysulfides. However, nonpolar carbon and polar LiPSs materials have poor affinity, and LiPSs can migrate from the carbon film and dissolve into the electrolyte, thus failing to effectively suppress the shuttle effect.

[0004] In addition, existing technologies can also use artificial SEI films, fluorinated electrolyte additives, or lithium anode carriers (such as carbon cloth or copper mesh) to suppress lithium dendrite growth, but none of the above methods can effectively suppress lithium dendrite growth. Summary of the Invention

[0005] The purpose of this invention is to provide a TiN-NbC nanofiber membrane, its preparation method and application, and lithium-sulfur batteries. The TiN-NbC nanofiber membrane prepared by this invention can effectively suppress the shuttle effect and lithium dendrite growth in lithium-sulfur batteries.

[0006] To achieve the objectives of this invention, the following technical solutions are provided:

[0007] A method for preparing a TiN-NbC nanofiber membrane includes the following steps:

[0008] A spinning solution is obtained by mixing a polymer, a titanium source, a niobium source, and an organic solvent.

[0009] The spinning solution is electrospun on the matrix surface to obtain a composite fiber precursor on the matrix surface.

[0010] The composite fiber precursor is carbonized to obtain the TiN-NbC nanofiber membrane on the matrix surface;

[0011] The polymer includes polyacrylonitrile and / or polyvinylpyrrolidone.

[0012] Preferably, the titanium source includes one or more of tetrabutyl titanate, titanium tetrachloride, and titanium sulfate; the niobium source includes niobium pentoxide and / or niobium chloride.

[0013] Preferably, the organic solvent includes one or more of N,N-dimethylformamide, acetone, and ethanol.

[0014] Preferably, the ratio of the polymer, titanium source and niobium source is 0.3-1.0g:1.0-2.5mL:0.1-1.0g.

[0015] Preferably, the conditions for electrospinning include:

[0016] The distance between the syringe spinneret and the receiver is 15–25 cm; the voltage is 15–20 kV; the relative humidity is 20%–40%; and the temperature is 20–30℃.

[0017] Preferably, the carbonization temperature is 600–900°C and the time is 2–4 hours.

[0018] The present invention also provides a TiN-NbC nanofiber membrane prepared by the preparation method described above, comprising carbon nanofibers and nanoparticles embedded in the pores of the carbon nanofibers; the nanoparticles are TiN particles and NbC particles.

[0019] The present invention also provides the application of the TiN-NbC nanofiber membrane in lithium-sulfur batteries.

[0020] Preferably, the TiN-NbC nanofiber membrane serves as the positive electrode membrane reactor and / or negative electrode protective layer in a lithium-sulfur battery.

[0021] The present invention also provides a lithium-sulfur battery, comprising a positive electrode shell, a positive electrode sheet, a separator, an electrolyte, a lithium sheet, a spring sheet, a gasket, and a negative electrode shell arranged sequentially.

[0022] A positive electrode membrane reactor is provided between the positive electrode sheet and the separator, and / or a negative electrode protective layer is provided between the separator and the lithium sheet;

[0023] The membrane reactor and / or negative electrode protective layer are the TiN-NbC nanofiber membranes described in the above technical solution.

[0024] This invention provides a method for preparing TiN-NbC nanofiber membranes, comprising the following steps: mixing a polymer, a titanium source, a niobium source, and an organic solvent to obtain a spinning solution; electrospinning the spinning solution on a substrate surface to obtain a composite fiber precursor on the substrate surface; and carbonizing the composite fiber precursor to obtain the TiN-NbC nanofiber membrane on the substrate surface. The polymer includes polyacrylonitrile and / or polyvinylpyrrolidone. This invention uses electrospinning and a high-temperature solid-state method to synthesize TiN-NbC / CNF membranes. The preparation method is simple, and there are no other ionic impurities besides titanium and niobium metal ions. At high temperatures, the polymer is completely converted into carbon, without introducing other impurity ions. Furthermore, TiN-NbC nanoparticles are uniformly embedded in nanofibers, effectively avoiding the stacking of TiN-NbC nanoparticles and ensuring the exposure of more active sites. The interwoven nanofibers form a three-dimensional conductive network, which can improve the electronic conductivity and contact area of ​​the TiN-NbC nanofiber membrane.

[0025] This invention also provides the application of the TiN-NbC nanofiber membrane described above in lithium-sulfur batteries. When the TiN-NbC nanofiber membrane is applied to the positive electrode membrane reactor of a lithium-sulfur battery, the lithium-sulfur battery exhibits better chemical stability, lower internal resistance, higher discharge specific capacity, and faster adsorption and conversion of lithium polysulfides, effectively suppressing the shuttle effect and thus demonstrating excellent electrochemical performance. When the TiN-NbC nanofiber membrane is applied to the negative electrode protective layer of a lithium-sulfur battery, it can introduce an artificial solid electrolyte interface (SEI), suppressing the growth of lithium dendrites. Furthermore, the cross-array of the TiN-NbC nanofiber membrane can regulate the uniform deposition behavior of lithium ions, effectively protecting the lithium negative electrode and extending the cycle life of the lithium-sulfur battery. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The XRD pattern of the TiN-NbC / CNF nanofiber membrane prepared in Example 1;

[0028] Figure 2 The image shows the morphology of the TiN-NbC / CNF nanofiber membrane prepared in Example 1.

[0029] Figure 3 The CV curves of the TiN-NbC / CNF membrane reactor cell prepared in Application Example 1 and the membrane-free reactor cell in Comparative Example 1 are shown in the potential range of 1.6–2.8 V.

[0030] Figure 4 The constant current charge-discharge (GCD) curves are shown for the TiN-NbC / CNF membrane reactor cell prepared in Application Example 1 and the membrane-free reactor cell in Comparative Example 1.

[0031] Figure 5 The rate performance graphs are for the TiN-NbC / CNF membrane reactor cell prepared in Application Example 1 and the membrane-free reactor cell in Comparative Example 1.

[0032] Figure 6 The cycling performance of the TiN-NbC / CNF membrane reactor cell prepared in Application Example 1 and the membrane-free reactor cell in Comparative Example 1 at a current density of 0.5C is compared.

[0033] Figure 7 The lithium-lithium symmetric cells with TiN-NbC / CNF film anode protective layer and the pure lithium anode cell of Comparative Example 1 were compared at 0.5–5 mA·cm⁻¹. -2 Voltage distribution diagrams under different current densities;

[0034] Figure 8 The constant current plating / stripping stability diagrams are shown for the battery with TiN-NbC / CNF film anode protective layer prepared in Application Example 2 and the pure lithium anode battery in Comparative Example 1. Detailed Implementation

[0035] This invention provides a method for preparing TiN-NbC / CNF nanofiber membranes, comprising the following steps:

[0036] A spinning solution is obtained by mixing a polymer, a titanium source, a niobium source, and an organic solvent.

[0037] The spinning solution is electrospun on the matrix surface to obtain a composite fiber precursor on the matrix surface.

[0038] The composite fiber precursor is carbonized to obtain the TiN-NbC nanofiber membrane on the matrix surface;

[0039] The polymer includes one or more of polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, and polyvinylidene fluoride.

[0040] In this invention, unless otherwise specified, all raw materials used in the preparation are preferably commercially available products well known to those skilled in the art.

[0041] This invention involves mixing a polymer, a titanium source, a niobium source, and an organic solvent to obtain a spinning solution. In this invention, the polymer comprises polyacrylonitrile (PAN) and / or polyvinylpyrrolidone (PVP), preferably polyacrylonitrile. Preferably, the polymer also includes polyvinyl alcohol and / or polyvinylidene fluoride; when the polymer contains polyvinyl alcohol and / or polyvinylidene fluoride, it contains at least one of polyacrylonitrile and polyvinylpyrrolidone. Preferably, the molecular weight of the polymer is between 10,000 and 1,000,000; the solubility of the polymer is preferably between 15% and 25%.

[0042] In this invention, the titanium source preferably includes one or more of tetrabutyl titanate, titanium tetrachloride and titanium sulfate, more preferably tetrabutyl titanate; the niobium source preferably includes niobium pentoxide and / or niobium chloride, more preferably niobium pentoxide.

[0043] In this invention, the organic solvent preferably includes one or more of N,N-dimethylformamide (DMF), acetone and ethanol, more preferably N,N-dimethylformamide.

[0044] In this invention, the preferred ratio of the polymer, titanium source, and niobium source is 0.3–1.0 g: 1.0–2.5 mL: 0.1–1.0 g, more preferably 0.6–0.9 g: 1.8–2.3 mL: 0.2–0.5 g. In this invention, the preferred ratio of the polymer and organic solvent is 0.3–1.0 g: 6–10 mL, more preferably 0.6–0.9 g: 7–9 mL.

[0045] In this invention, the mixing is preferably by stirring, more preferably by magnetic stirring; the mixing time is preferably 2-5 hours, more preferably 3-4 hours. This invention does not impose any particular limitation on the stirring rate.

[0046] After obtaining the spinning solution, the present invention performs electrospinning on the substrate surface to obtain a composite fiber precursor on the substrate surface. In the present invention, the substrate is preferably one of aluminum foil, glass plate, and nonwoven fabric, and more preferably aluminum foil.

[0047] In this invention, the electrospinning conditions preferably include: the distance between the syringe spinneret and the receiver is preferably 15-25 cm, more preferably 19-21 cm; the voltage is preferably 15-20 kV, more preferably 18-19 kV; the relative humidity is preferably 20%-40%, more preferably 25-30%; and the temperature is preferably 20-30°C, more preferably 22-25°C.

[0048] After obtaining the composite fiber precursor, the present invention carbonizes the composite fiber precursor to obtain the TiN-NbC nanofiber membrane on the matrix surface.

[0049] In this invention, the carbonization temperature is preferably 600–900°C, more preferably 700–800°C; the time is preferably 2–4 hours, more preferably 2.5–3.5 hours; the carbonization is preferably carried out under a protective atmosphere; the protective atmosphere is preferably one or more of hydrogen, helium, and argon, more preferably hydrogen and argon; the volume ratio of hydrogen to argon is preferably 5–10:95–90. In this invention, the heating rate to the carbonization temperature is preferably 200–300°C / min, more preferably 220–250°C / min.

[0050] The present invention also provides a TiN-NbC nanofiber membrane prepared by the preparation method described above, wherein the TiN-NbC nanofiber membrane comprises carbon nanofibers and nanoparticles embedded in the pores of the carbon nanofibers; the nanoparticles are TiN particles and NbC particles.

[0051] In this invention, the thickness of the TiN-NbC nanofiber membrane is preferably 10-200 μm, more preferably 50-100 μm.

[0052] The present invention also provides the application of the TiN-NbC nanofiber membrane described in the above technical solution in lithium-sulfur batteries.

[0053] In this invention, the TiN-NbC nanofiber membrane is preferably used as the positive electrode membrane reactor and / or negative electrode protective layer in a lithium-sulfur battery.

[0054] The present invention also provides a lithium-sulfur battery, comprising a positive electrode shell, a positive electrode sheet, a separator, an electrolyte, a lithium sheet, a spring sheet, a gasket, and a negative electrode shell arranged sequentially.

[0055] A membrane reactor is provided between the positive electrode and the separator, and / or a negative electrode protective layer is provided between the separator and the lithium sheet;

[0056] The membrane reactor or negative electrode protective layer is the TiN-NbC nanofiber membrane described in the above technical solution.

[0057] In this invention, the positive electrode shell is preferably a stainless steel shell; the positive electrode sheet is preferably a sulfur-carbon coated aluminum foil; the separator sheet is preferably a polypropylene (PP) membrane; the electrolyte is preferably a 1 mol / L LiPF6 electrolyte; the spring sheet is preferably a stainless steel spring sheet; the gasket is preferably a stainless steel gasket; and the negative electrode shell is preferably a stainless steel shell.

[0058] In this invention, the lithium-sulfur battery is preferably assembled in a glove box with a water content and oxygen content of less than 0.01 ppm; the lithium-sulfur battery is preferably assembled from bottom to top in the following order: negative electrode shell, sulfur-carbon positive electrode sheet, membrane reactor, separator, electrolyte, lithium sheet, gasket, spring sheet, and positive electrode shell; and the assembled lithium-sulfur battery is sealed using a sealing machine.

[0059] To further illustrate the present invention, the TiN-NbC nanofiber membrane, its preparation method, its application, and lithium-sulfur batteries provided by the present invention are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] 0.6 g PAN, 1.8 mL tetrabutyl titanate and 0.2 g niobium pentoxide were dissolved in 7 mL DMF and magnetically stirred at room temperature for 2 h to form a uniform spinning solution.

[0062] The above spinning solution was loaded into a syringe, with a distance of 20 cm between the syringe spinneret and the receiver. Electrospinning was performed on a rotating aluminum foil at a voltage of 19 kV to obtain a composite fiber precursor.

[0063] The composite fiber precursor was heated to 900℃ at a heating rate of 200℃ / min in an H2 / Ar (volume ratio of 5:95) atmosphere, carbonized at 900℃ for 3h, and then cooled to room temperature to obtain a TiN-NbC nanofiber membrane, denoted as TiN-NbC / CNF.

[0064] Application Example 1

[0065] The lithium-sulfur battery was assembled in the following order from bottom to top: stainless steel negative electrode shell, sulfur / KB composite positive electrode sheet, positive electrode membrane reactor (TiN-NbC / CNF prepared in Example 1), PP separator, 1 mol / L LiPF6 electrolyte, lithium negative electrode, stainless steel gasket, stainless steel spring sheet, and stainless steel positive electrode shell. The assembly was carried out in a glove box with water and oxygen contents both below 0.01 ppm. The assembled lithium-sulfur battery was then sealed with a sealing machine to obtain a lithium-sulfur battery with a TiN-NbC / CNF membrane reactor.

[0066] Application Example 2

[0067] The lithium-sulfur battery was assembled in the following order from bottom to top: stainless steel negative electrode shell, sulfur / KB composite positive electrode sheet, PP separator, negative electrode protective layer (TiN-NbC / CNF prepared in Example 1), 1 mol / L LiPF6 electrolyte, lithium sheet, stainless steel gasket, stainless steel spring sheet, and stainless steel positive electrode shell. The assembly was carried out in a glove box with water and oxygen contents both below 0.01 ppm. The assembled lithium-sulfur battery was then sealed using a sealing machine.

[0068] Comparative Example 1

[0069] The lithium-sulfur battery is assembled according to the assembly method described in Application Example 1, except that a positive electrode membrane reactor is not provided. The lithium-sulfur battery is referred to as Blank.

[0070] Comparative Example 2

[0071] The lithium-sulfur battery is assembled according to the assembly method described in Application Example 2, except that the negative electrode is a pure lithium negative electrode and no negative electrode protective layer is provided, denoted as Pristine Li.

[0072] Test Example 1

[0073] The phase composition of the TiN-NbC / CNF film prepared in Example 1 was analyzed by X-ray diffraction (XRD), and the results are shown below.

[0074] Figure 1 The XRD pattern of the TiN-NbC / CNF nanofiber membrane prepared in Example 1 is shown below. Figure 1 The XRD pattern of the TiN-NbC / CNF film shows two phases, TiN and NbC. Two sharp diffraction peaks at 42.5° (200) and 62.0° (220) and three low diffraction peaks at 36.6° (111), 74.3° (311), and 78.3° (222) correspond to TiN (JCPDS NO. 38-1420). Four low diffraction peaks at 34.7° (111), 40.3° (200), 58.3° (220), 73.3° (222), and 87.1° (400) correspond to NbC (JCPDS NO. 38-1420). No extraneous impurity peaks were found in the XRD pattern, indicating that the prepared TiN-NbC / CNF nanofiber film consists of two pure crystalline phases.

[0075] Figure 2 The image shows the morphology of the TiN-NbC / CNF nanofiber membrane prepared in Example 1. Figure 2 It is known that the TiN-NbC / CNF nanofiber membrane prepared by the present invention is composed of nanofibers and TiN particles and NbC particles embedded in the pores of the nanofibers.

[0076] Test Example 2

[0077] The electrochemical performance of the lithium-sulfur batteries prepared for Example 1 and Comparative Example 1 was tested at room temperature (25℃). A CT2001 Blue Electric Battery Testing System from Wuhan Blue Electric Electronics Co., Ltd. was used to perform constant current charge-discharge (GCD) tests to analyze the rate performance, cycle stability, and coulombic efficiency of the batteries. The test voltage range was 1.6–2.8V. A Bio-Logic VMP-3 multichannel electrochemical workstation from Bio-Logic, France, was used to perform electrochemical cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS, AC perturbation of 5mV, frequency range 100kHz–0.01Hz). The peak positions and overlap of the CV curves were used to determine the extent and stability of the electrochemical reaction. The electrode process kinetics were studied based on the EIS test results, as shown below.

[0078] Figure 3 The CV curves for the TiN-NbC / CNF membrane reactor cell prepared in Example 1 and the membrane-free reactor cell in Comparative Example 1 are shown in the potential range of 1.6–2.8 V. Figure 3 It can be seen that at a scan rate of 0.1 mV·s -1 At that time, the CV curve showed obvious cathode and anodic peaks, indicating that elemental S could be reversibly oxidized to Li₂S₂ / Li₂S and reduced to S. Compared with the cell without a membrane reactor, the cell with the TiN-NbC / CNF membrane reactor showed stronger anodic and cathode peaks, indicating stronger redox kinetics. Furthermore, TiN-NbC / CNF exhibited the smallest potential difference between the oxidation and reduction peaks, suggesting that the introduction of TiN-NbC / CNF was beneficial to the nucleation and deposition process of Li₂S, and could better suppress electrochemical polarization, thereby enhancing the electrochemical reaction kinetics.

[0079] Figure 4 The constant current charge-discharge (GCD) curves of the TiN-NbC / CNF membrane reactor cell prepared in Example 1 and the membrane-free reactor cell in Comparative Example 1 are obtained from... Figure 4 It can be seen that the discharge plateaus at -0.2V and -0.5V in the GCD curve correspond to the conversion of Li₂Sn to S₈ and Li₂Sn to Li₂S / Li₂S₂, respectively, while the charging plateau at 2.2–2.4V corresponds to the oxidation of Li₂S to S. Compared to batteries without a membrane reactor, batteries with a TiN-NbC / CNF membrane reactor exhibit lower charging voltage, higher discharging voltage, and smaller potential difference ΔE. This indicates that the presence of the TiN-NbC / CNF membrane reactor can improve the redox reaction kinetics of S and reduce electrochemical polarization.

[0080] Figure 5 The rate performance diagrams are for the TiN-NbC / CNF membrane reactor cell prepared in Application Example 1 and the membrane-free reactor cell in Comparative Example 1. Figure 5 It can be seen that the discharge specific capacities of the TiN-NbC / CNF membrane reactor battery with the positive electrode side at 0.1, 0.2, 0.5, 1, 2, 3, 4 and 5C are 1314, 1185, 1085, 1027, 965, 926, 899 and 877 mAh·g, respectively. -1 This is significantly higher than that of batteries without a membrane reactor (discharge specific capacities at 0.1, 0.2, 0.5, 1, 2, 3, 4, and 5C are 983, 884, 636, 316, 100, 44, 13, and 18 mAh·g, respectively). -1 When the current recovers to 0.1C, the discharge specific capacity is still as high as 1404 mAh·g. -1 The excellent rate performance demonstrates that the interaction between TiN-NbC materials and nanofibers has a good ability to capture polysulfides and accelerate electron / ion transfer rates.

[0081] Figure 6 The cycling performance of the TiN-NbC / CNF membrane reactor cell prepared in Example 1 and the membrane-free reactor cell in Comparative Example 1 at a current density of 0.5C was compared by... Figure 6 It can be seen that the TiN-NbC / CNF membrane reactor battery has an output specific capacity of 1123 mAh·g. -1 After 200 cycles, the battery's specific capacity still reaches 980 mAh·g. -1 It is higher than that of membrane-free reactor batteries (initial specific capacity of 617 mAh·g). -1 After 200 cycles, the stable specific capacity is 440 mAh·g. -1 This excellent cycling performance is due to the good adsorption of polysulfides by TiN-NbC and the good blocking of polysulfide shuttle by nanofibers.

[0082] Test Example 3

[0083] The electrochemical performance of the lithium-sulfur batteries prepared in corresponding use case 2 and comparative example 2 was tested using the instruments and methods described in 1. The results are shown below.

[0084] Figure 7 The battery with a TiN-NbC / CNF film anode protective layer prepared in Application Example 2 and the pure lithium anode battery in Comparative Example 1 were tested at 0.5–5 mA·cm⁻¹. -2 Voltage distribution diagrams under different current densities; Figure 8 The constant current plating / stripping stability diagrams are shown for the battery with a TiN-NbC / CNF film anode protective layer prepared in Application Example 2 and the pure lithium anode battery in Comparative Example 1. Figure 7 and Figure 8 It can be seen that as the current density increases from 0.5 mA·cm -2 Increased to 5 mA·cm-2 The overvoltage of the TiN-NbC / CNF-Li electrode increases slowly, even at 5 mA·cm⁻¹. -2 Even at 2 mA·cm⁻¹, the TiN-NbC / CNF-Li electrode maintains good stability with an overpotential of only 78.1 mV, indicating a significant improvement in kinetics and reversibility compared to the pure lithium anode. -2 At high current densities, the TiN-NbC / CNF-Li electrode maintains good stability and low overpotential after 800 cycles, while the pure lithium electrode exhibits a large overpotential and poor stability after approximately 170 cycles. The active sites of TiN-NbC / CNF can regulate the initial and subsequent electroplating processes of Li, improving the reversibility of plating / stripping and extending the cycle life of the Li electrode.

[0085] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a TiN-NbC nanofiber membrane, characterized in that, Includes the following steps: A spinning solution is obtained by mixing a polymer, a titanium source, a niobium source, and an organic solvent; the titanium source includes one or both of tetrabutyl titanate and titanium tetrachloride. The spinning solution is electrospun on the matrix surface to obtain a composite fiber precursor on the matrix surface. The composite fiber precursor is carbonized to obtain the TiN-NbC nanofiber film on the matrix surface; the carbonization is carried out under a protective atmosphere; the carbonization temperature is 600~900℃ and the time is 2~4h. The polymer includes polyacrylonitrile and / or polyvinylpyrrolidone; The TiN-NbC nanofiber membrane comprises carbon nanofibers and nanoparticles embedded in the pores of the carbon nanofibers; the nanoparticles are TiN particles and NbC particles; the TiN-NbC nanofiber membrane serves as a positive electrode membrane reactor and / or a negative electrode protective layer in a lithium-sulfur battery.

2. The preparation method according to claim 1, characterized in that, The niobium source includes niobium pentoxide and / or niobium chloride.

3. The preparation method according to claim 1, characterized in that, The organic solvent includes one or more of N,N-dimethylformamide, acetone, and ethanol.

4. The method of claim 1, wherein, The ratio of the polymer, titanium source, and niobium source used is 0.3~1.0g:1.0~2.5mL:0.1~1.0g.

5. The preparation method according to claim 1, characterized in that, The conditions for electrospinning include: a distance of 15-25 cm between the syringe spinneret and the receiver; a voltage of 15-20 kV; a relative humidity of 20%-40%; and a temperature of 20-30°C.

6. A lithium-sulfur battery, characterized by, It includes a positive electrode shell, a positive electrode plate, a separator, an electrolyte, a lithium plate, a spring sheet, a gasket, and a negative electrode shell arranged in sequence; A positive electrode membrane reactor is provided between the positive electrode sheet and the separator, and / or a negative electrode protective layer is provided between the separator and the lithium sheet; The membrane reactor and / or negative electrode protective layer are TiN-NbC nanofiber membranes prepared by the preparation method according to any one of claims 1 to 5.

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