A zirconium-based flexible nanocarbon fiber membrane, a preparation method thereof, and a lithium-sulfur battery positive electrode and a lithium-sulfur battery

Abstract

This invention belongs to the field of lithium-sulfur battery technology, providing a zirconium-based flexible carbon nanofiber membrane, its preparation method, a lithium-sulfur battery cathode, and a lithium-sulfur battery. The preparation method involves mixing a zirconium source, a polymer, and an organic solvent to form a spinning solution; the spinning solution is electrospun to obtain a fiber membrane; the fiber membrane is then carbonized to obtain the zirconium-based flexible carbon nanofiber membrane. This invention yields a zirconium-based flexible carbon nanofiber membrane with high conductivity, a well-structured microstructure, and active sites for zirconium-based compound nanoparticles. The zirconium-based flexible carbon nanofiber membrane with its well-structured microstructure and active sites for zirconium-based compound nanoparticles exhibits excellent chemical / physical adsorption characteristics for polysulfides. Simultaneously, the zirconium-based compound nanoparticles possess excellent electrocatalytic properties, accelerating efficient conversion between polysulfides, achieving efficient electron transfer and ion diffusion, and realizing high sulfur utilization. This results in excellent areal capacity electrochemical performance. When used as a cathode in lithium-sulfur batteries, it enables the lithium-sulfur battery to exhibit outstanding rate performance and cycle stability, promoting the development of lithium-sulfur batteries towards low-altitude economic applications. Furthermore, the zirconium-based flexible carbon nanofiber membrane, when combined with a high-sulfur-loaded sulfur cathode (greater than 6 mg / cm³), further enhances the effectiveness of the process. 2 Together, they constructed a novel "sandwich" sulfur cathode, resulting in a high-capacity lithium-sulfur battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-sulfur battery technology, and in particular to a zirconium-based flexible carbon nanofiber membrane, its preparation method, a lithium-sulfur battery cathode, and a lithium-sulfur battery. Background Technology

[0002] The limited energy density of mainstream lithium-ion batteries makes them unsuitable for high-energy-density devices, while lithium-sulfur (Li-S) batteries have attracted considerable attention due to their theoretical energy density of 2600 Wh / kg. Despite the compelling advantages of Li-S batteries, their practical applications remain uncertain, primarily due to several technical challenges. Typically, the inherently poor electronic / ionic conductivity of sulfur and its multi-electron solid-liquid transitions determine the slow kinetics of sulfur electrochemical reactions. Furthermore, the strong solvation of intermediate lithium polysulides (LiPS) in ether-based electrolytes leads to significant loss of active material, and the round-trip migration of LiPS further induces the so-called "shuttle effect," resulting in low coulombic efficiency and poor cycleability.

[0003] The aforementioned fundamental problems have existed from the very beginning of the design of Li-S battery systems. As battery performance continues to improve towards ultimate commercialization goals, various derivative problems are gradually being resolved. Over the past decade, laboratories worldwide have been conducting fundamental research on lithium batteries, which, while bringing promising performance improvements, has also gradually unraveled the mysteries. However, to date, most laboratory-scale progress has been based on sulfur loadings below 2 mg / cm³. 2 The current lithium-sulfur batteries are far below the requirements for practical applications. Therefore, research on high sulfur loading is crucial to bridging the gap between laboratory-scale research and industrialization.

[0004] Therefore, researchers have a responsibility to verify the feasibility and stability of lithium-sulfur batteries on a larger scale. Based on previously reported calculations, to achieve the high energy density expected in Li-S batteries, the areal loading of sulfur needs to be greater than 5 mg / cm³. 2 Unfortunately, a simple scaling-up from low-sulfur-loading electrode configurations to high-sulfur-loading lithium-sulfur batteries is impractical because thicker electrode layers introduce entirely new challenges, such as low sulfur utilization efficiency, shuttle effects, and poor chemical conversion kinetics, ultimately resulting in an areal capacity of less than 4 mAh / cm² for lithium-sulfur batteries. 2 Therefore, how to achieve high sulfur loading (5 mg / cm³) 2 Achieving excellent areal capacity (≥4mAh / cm³) under the condition of 2 This has become a challenge that the energy storage field needs to overcome. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a zirconium-based flexible carbon nanofiber membrane, its preparation method, and a lithium-sulfur battery membrane reactor. The zirconium-based flexible carbon nanofiber membrane prepared by the method provided by this invention improves the sulfur loading, specific capacity, and areal capacity of lithium-sulfur batteries.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a zirconium-based flexible carbon nanofiber membrane, comprising the following steps:

[0008] A zirconium source, a polymer, and an organic solvent are mixed to form a spinning solution;

[0009] The spinning solution is electrospun to obtain a fiber membrane;

[0010] The fiber membrane is carbonized to obtain the zirconium-based flexible carbon nanofiber membrane.

[0011] Preferably, the zirconium source includes an organic zirconium source and / or an inorganic zirconium source, wherein the organic zirconium source includes tetrabutyl zirconate and / or zirconium dichlorocerocene, and the inorganic zirconium source includes zirconium chloride.

[0012] Preferably, the polymer comprises polyacrylonitrile and / or polyvinylpyrrolidone.

[0013] Preferably, the organic solvent includes N,N-dimethylformamide and / or N-methylpyrrolidone.

[0014] Preferably, the ratio of the zirconium source, polymer, and organic solvent is 2-10 mL: 0.6-2.0 g: 5-20 mL.

[0015] Preferably, the spinning solution further includes a pore-forming agent; the pore-forming agent includes one or more of polystyrene, polymethyl methacrylate and paraffin; the mass ratio of the pore-forming agent to the polymer is 0.1-1:0.6-2.0.

[0016] Preferably, the carbonization temperature is 600℃~1400℃, and the time is 1~16h; the heating rate to the carbonization temperature is 1℃ / min~10℃ / min; the carbonization includes nitrogen, argon, ammonia, selenium-containing atmosphere or tellurium-containing atmosphere.

[0017] The present invention also provides a zirconium-based flexible carbon nanofiber membrane prepared by the preparation method described above.

[0018] The present invention also provides a lithium-sulfur battery cathode, comprising a first membrane reactor, a sulfur cathode, and a second membrane reactor stacked together; the first membrane reactor and the second membrane reactor are zirconium-based flexible carbon nanofiber membranes as described in the above technical solution.

[0019] The present invention also provides a lithium-sulfur battery, comprising a positive electrode, a lithium negative electrode, an electrolyte, and a separator;

[0020] The positive electrode is the positive electrode of the lithium-sulfur battery described in the above technical solution.

[0021] This invention provides a method for preparing a zirconium-based flexible carbon nanofiber membrane, comprising the following steps: mixing a zirconium source, a polymer and an organic solvent to form a spinning solution; electrospinning the spinning solution to obtain a fiber membrane; and carbonizing the fiber membrane to obtain the zirconium-based flexible carbon nanofiber membrane.

[0022] This invention involves electrospinning a spinning solution composed of a zirconium source and a polymer to form a fiber membrane, followed by carbonization of the fiber membrane to obtain a zirconium-based flexible carbon nanofiber membrane with high conductivity, a well-structured microstructure, and zirconium-based compound nanoparticles as active sites. This zirconium-based flexible carbon nanofiber membrane with its well-structured microstructure and zirconium-based compound nanoparticle active sites exhibits excellent chemical / physical adsorption properties for polysulfides. Simultaneously, the zirconium-based compound nanoparticles possess excellent electrocatalytic properties, accelerating efficient conversion between polysulfides, achieving efficient electron transfer and ion diffusion, and realizing high sulfur utilization. This results in excellent areal capacity electrochemical performance. When used as a cathode in lithium-sulfur batteries, it enables the batteries to exhibit outstanding rate performance and cycle stability, promoting the development of lithium-sulfur batteries towards low-altitude economic applications. Furthermore, the zirconium-based flexible carbon nanofiber membrane, when used with a high-sulfur-loaded sulfur cathode (greater than 6 mg / cm³), further enhances its effectiveness. 2 Together, they constructed a novel "sandwich" sulfur cathode, resulting in a lithium-sulfur battery with high specific capacity and areal capacity. Attached Figure Description

[0023] Figure 1 A digital photograph of the zirconium-based flexible carbon nanofiber membrane obtained in Example 1;

[0024] Figure 2 The image shows the XRD pattern of the zirconium-based flexible carbon nanofiber membrane obtained in Example 1.

[0025] Figure 3 XPS test image of the zirconium-based flexible carbon nanofiber membrane obtained in Example 2;

[0026] Figure 4 Thermogravimetric analysis (TGA) results of the zirconium-based flexible carbon nanofiber membrane obtained in Example 3 are shown below.

[0027] Figure 5 The graph shows the cycle performance test results of the coin-type lithium-sulfur battery assembled in Example 3.

[0028] Figure 6 The graph shows the cycle performance test results of the coin-type lithium-sulfur battery assembled in Example 4.

[0029] Figure 7 The graph shows the cycle performance test results of the coin-type lithium-sulfur battery assembled in Example 6. Detailed Implementation

[0030] This invention provides a method for preparing a zirconium-based flexible carbon nanofiber membrane, comprising the following steps:

[0031] A zirconium source, a polymer, and an organic solvent are mixed to form a spinning solution;

[0032] The spinning solution is electrospun to obtain a fiber membrane;

[0033] The fiber membrane is carbonized to obtain the zirconium-based flexible carbon nanofiber membrane.

[0034] Unless otherwise specified, all raw materials used in this invention are preferably commercially available products.

[0035] This invention mixes a zirconium source, a polymer, and an organic solvent to form a spinning solution.

[0036] In this invention, the zirconium source preferably includes an organic zirconium source and / or an inorganic zirconium source, the organic zirconium source preferably includes tetrabutyl zirconate and / or zirconium dichlorocerocene, and the inorganic zirconium source preferably includes zirconium chloride.

[0037] In this invention, the polymer preferably includes polyacrylonitrile (PAN) and / or polyvinylpyrrolidone (PVP).

[0038] In this invention, the organic solvent preferably includes N,N-dimethylformamide (DMF) and / or N-methylpyrrolidone (NMP).

[0039] In this invention, the preferred ratio of zirconium source, polymer and organic solvent is 2-10 mL: 0.6-2.0 g: 5-20 mL.

[0040] In this invention, the spinning solution preferably further includes a pore-forming agent, which preferably includes one or more of polystyrene (PS), polymethyl methacrylate (PMMA), and paraffin wax. In this invention, the mass ratio of the pore-forming agent to the polymer is preferably 0.1–1:0.6–2.0. In this invention, the addition of a pore-forming agent enables the preparation of zirconium-based flexible carbon nanofiber membranes with porous, core-shell, hollow, or perforated microstructures; without the addition of a pore-forming agent, the resulting zirconium-based flexible carbon nanofiber membrane has a one-dimensional microstructure.

[0041] In this invention, the mixing temperature of the zirconium source, polymer and organic solvent is preferably room temperature, and the mixing time is preferably 3 to 20 hours; the mixing of the zirconium source, polymer and organic solvent is preferably carried out under stirring conditions.

[0042] After obtaining the spinning solution, the present invention performs electrospinning on the spinning solution to obtain a fiber membrane.

[0043] In this invention, the parameters of the electrospinning include: the ambient temperature is preferably 20-30℃, the ambient humidity is preferably ≤30%RH, the positive voltage is preferably ≥5KV, more preferably 18KV, the negative voltage is preferably ≤-0.1KV, more preferably -2KV, and the product collection distance is preferably 5cm-20cm.

[0044] In this invention, the thickness of the fiber membrane is preferably 50 μm to 1500 μm.

[0045] After obtaining the fiber membrane, the present invention carbonizes the fiber membrane to obtain the zirconium-based flexible carbon nanofiber membrane.

[0046] In this invention, the carbonization temperature is preferably 600℃~1400℃, more preferably 700~600℃; the time is preferably 1~16h, more preferably 5~10h; the heating rate to the carbonization temperature is preferably 1℃ / min~10℃ / min; the carbonization atmosphere preferably includes nitrogen, argon, ammonia, a selenium-containing atmosphere, or a tellurium-containing atmosphere. In this invention, the selenium-containing atmosphere is preferably obtained by heating selenium powder at high temperature, and the ratio of selenium powder to zirconium source is preferably ≥500mg:3mL, more preferably 1000mg:3mL. In this invention, the tellurium-containing atmosphere is preferably obtained by heating tellurium powder at high temperature, and the ratio of tellurium powder to zirconium source is preferably ≥500mg:3mL, more preferably 1000mg:3mL.

[0047] In this invention, during the carbonization process, the pore-forming agent decomposes and is eventually discharged as a gas, forming a porous structure.

[0048] This invention also provides a zirconium-based flexible carbon nanofiber membrane prepared by the preparation method described above. In this invention, the specific surface area of ​​the zirconium-based flexible carbon nanofiber membrane is preferably 60–600 m² / g. 2 / g, the zirconium-based flexible carbon nanofiber membrane has a microporous structure.

[0049] In this invention, the zirconium-based flexible carbon nanofiber membrane is formed by freely interwoven carbon nanofibers, and the microstructure of the zirconium-based flexible carbon nanofiber membrane is one or more of the following: one-dimensional, porous, core-shell, hollow, and hollow structures. When the spinning solution does not contain a pore-forming agent, the zirconium-based flexible carbon nanofiber membrane has a one-dimensional structure; when the spinning solution contains a pore-forming agent, the zirconium-based flexible carbon nanofiber membrane has one or more of the following: porous, core-shell, hollow, and hollow structures.

[0050] In this invention, the active sites of the zirconium-based flexible carbon nanofiber membrane are preferably zirconium-based compound nanoparticles, which preferably contain zirconium oxide (ZrO2). When the carbonization atmosphere is ammonia, the zirconium-based compound nanoparticles preferably also contain zirconium nitride, which preferably contains ZrN or Zr3N4; when the carbonization atmosphere is a selenium-containing atmosphere or a tellurium-containing atmosphere, the zirconium-based compound nanoparticles preferably also contain zirconium selenide (ZrSe3) or zirconium telluride (Te2Zr).

[0051] In this invention, the constituent elements of the zirconium-based flexible carbon nanofiber membrane preferably include zirconium (Zr), oxygen (O), nitrogen (N) and carbon (C).

[0052] In this invention, the atomic percentage of zirconium in the zirconium-based flexible carbon nanofiber membrane is preferably 20-80%, the atomic percentage of oxygen is preferably 1-30%, the atomic percentage of carbon is preferably 10-60%, and the atomic percentage of nitrogen is preferably 12-24%. When the carbonization atmosphere is a selenium-containing atmosphere or a tellurium-containing atmosphere, the atomic percentage of selenium in the zirconium-based flexible carbon nanofiber membrane is preferably 10-20%, and the atomic percentage of tellurium is preferably 10-20%.

[0053] In this invention, the bonds in the zirconium-based flexible carbon nanofiber membrane preferably include carbon-carbon double bonds (C=C), carbon-oxygen bonds (CO), oxygen-zirconium bonds (O-Zr), and zirconium-nitrogen bonds (N-Zr); when the carbonization atmosphere is a selenium-containing atmosphere or a tellurium-containing atmosphere, the bonds in the zirconium-based flexible carbon nanofiber membrane preferably also include selenium-zirconium bonds (Se-Zr) or tellurium-zirconium bonds (Te-Zr).

[0054] The present invention also provides a lithium-sulfur battery cathode, comprising a first membrane reactor, a sulfur cathode, and a second membrane reactor stacked together; the first membrane reactor and the second membrane reactor are zirconium-based flexible carbon nanofiber membranes as described in the above technical solution.

[0055] The lithium-sulfur battery cathode provided by the present invention includes a first membrane reactor, which is the zirconium-based flexible carbon nanofiber membrane described in the above technical solution.

[0056] The lithium-sulfur battery cathode provided by this invention includes a sulfur cathode, preferably a conventional sulfur cathode, which is preferably an electrode formed by grinding and coating an activated carbon / sulfur composite material. In this invention, the sulfur surface loading of the conventional sulfur cathode is ≥6 mg / cm³. 2 .

[0057] The lithium-sulfur battery cathode provided by the present invention includes a second membrane reactor, which is the zirconium-based flexible carbon nanofiber membrane described in the above technical solution.

[0058] The present invention also provides a lithium-sulfur battery, comprising a positive electrode, a lithium negative electrode, an electrolyte, and a separator;

[0059] The positive electrode is the positive electrode of the lithium-sulfur battery described in the above technical solution.

[0060] The lithium-sulfur battery provided by the present invention includes a positive electrode, which is the positive electrode of the lithium-sulfur battery described in the above technical solution.

[0061] The lithium-sulfur battery provided by this invention includes a lithium anode.

[0062] The lithium-sulfur battery provided by the present invention includes an electrolyte.

[0063] The lithium-sulfur battery provided by the present invention includes a separator.

[0064] The present invention does not specifically limit the materials of the lithium anode, electrolyte and separator, and can use lithium anode, electrolyte and separator of lithium-sulfur battery that are well known to those skilled in the art.

[0065] In this invention, the lithium-sulfur battery is preferably a button-type lithium-sulfur battery, a pouch-type lithium-sulfur battery, or a cylindrical lithium-sulfur battery.

[0066] The present invention does not impose specific limitations on the assembly method of the positive electrode, lithium negative electrode, electrolyte and separator; those skilled in the art can make the settings according to actual needs.

[0067] The following detailed description, in conjunction with embodiments, illustrates the zirconium-based flexible carbon nanofiber membrane, its preparation method, lithium-sulfur battery cathode, and lithium-sulfur battery provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0068] Example 1

[0069] 5 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.2 g of polyvinylpyrrolidone, and 0.6 g of polystyrene were dissolved together in a 50 mL beaker and stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun under conditions of ≤30% RH and 20℃, using a positive voltage of 18 kV and a negative voltage of -2 kV, with a product collection distance of 8 cm, to obtain a fiber membrane with a thickness of 1000 μm. The collected fiber membrane was then carbonized at 1000℃ for 1 hour in a high-purity nitrogen atmosphere (heating rate of 5℃ / min) to obtain a zirconium-based flexible carbon nanofiber membrane with zirconium dioxide (ZrO2) as the active site.

[0070] Figure 1 A digital photograph of the obtained zirconium-based flexible carbon nanofiber membrane, from Figure 1 It can be seen that the material still exhibits excellent flexibility after high-temperature carbonization.

[0071] Figure 2The XRD pattern of the obtained zirconium-based flexible carbon nanofiber membrane is shown below. Figure 2 It can be seen that the zirconium-based active sites of the flexible carbon nanofiber membrane synthesized by this method are zirconium dioxide (ZrO2).

[0072] The obtained zirconium-based flexible carbon nanofiber membrane was cut into circular models of equal size (14 mm in diameter) to serve as membrane reactors, with a sulfur surface loading of 6 mg / cm³. 2 Using ordinary sulfur cathodes, a novel "sandwich" sulfur cathode is constructed and assembled with commercial electrolytes, separators, and lithium sheets to form coin-type lithium-sulfur batteries.

[0073] The sulfur loading of the resulting coin-type lithium-sulfur battery was 6 mg / cm³. 2 It has a specific capacity of 1133.5 mAh / g and an areal capacity of 6.8 mAh / cm³. 2 .

[0074] Example 2

[0075] 3 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.0 g of polyvinylpyrrolidone, and 0.5 g of polystyrene were dissolved together in a 50 mL beaker and stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun under conditions of ≤30% RH and 20℃, using a positive voltage of 18 kV and a negative voltage of -2 kV, with a product collection distance of 10 cm, to obtain a fiber membrane with a thickness of 1200 μm. The collected fiber membrane was then carbonized at 800℃ for 3 hours in a high-purity ammonia atmosphere (heating rate of 5℃ / min) to obtain a zirconium-based flexible carbon nanofiber membrane with zirconium nitride (Zr3N4) as the active site.

[0076] Figure 3 The XPS plot of the obtained zirconium-based flexible carbon nanofiber membrane is shown below. Figure 3 It can be seen that the synthesized material contains the elements C, O, Zr, and N.

[0077] The obtained zirconium-based flexible carbon nanofiber membrane was cut into circular models of equal size (14 mm in diameter) to serve as membrane reactors, with a sulfur surface loading of 8 mg / cm³. 2 Using ordinary sulfur cathodes, a novel "sandwich" sulfur cathode is constructed and assembled with commercial electrolytes, separators, and lithium sheets to form coin-type lithium-sulfur batteries.

[0078] The resulting coin cell lithium-sulfur battery has an areal load of 6 mg / cm³. 2 It has a specific capacity of 1066.8 mAh / g and an areal capacity of 6.4 mAh / cm². 2 .

[0079] Example 3

[0080] 3 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.0 g of polyvinylpyrrolidone, and 0.5 g of polystyrene were dissolved in a 50 mL beaker. Then, 1 g of selenium (Se) powder was added and the mixture was stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun under conditions of ≤30% RH and 20℃, using a positive voltage of 18 kV and a negative voltage of -2 kV, with a product collection distance of 10 cm, to obtain a fiber membrane with a thickness of 800 μm. The collected fiber membrane was carbonized at 600℃ for 16 hours in a high-purity argon atmosphere (heating rate of 2℃ / min) to obtain a zirconium-based flexible carbon nanofiber membrane with zirconium selenide (ZrSe3) as the active site.

[0081] Figure 4 Thermogravimetric analysis (TGA) curves of the obtained zirconium-based flexible carbon nanofiber membranes; from Figure 4 It can be seen that Zr atoms account for 75% of the mass of the material.

[0082] The obtained zirconium-based flexible carbon nanofiber membrane was cut into circular models of equal size (14 mm in diameter) to serve as membrane reactors, with a sulfur surface loading of 6 mg / cm³. 2 Using ordinary sulfur cathodes, a novel "sandwich" sulfur cathode is constructed and assembled with commercial electrolytes, separators, and lithium sheets to form coin-type lithium-sulfur batteries.

[0083] Figure 5 Cycle performance test results for assembled coin-type lithium-sulfur batteries; from Figure 5 It can be seen that this lithium-sulfur battery achieves high-capacity cycling at a rate of 0.5C.

[0084] The resulting coin cell lithium-sulfur battery has an areal load of 6 mg / cm³. 2 It has a specific capacity of 1116.7 mAh / g and an areal capacity of 6.7 mAh / cm². 2 .

[0085] Example 4

[0086] 4 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.2 g of polyvinylpyrrolidone, and 0.6 g of polystyrene were dissolved in a 50 mL beaker. Then, 1 g of tellurium (Te) powder was added and the mixture was stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun under conditions of ≤30% RH and 20℃, using a positive voltage of 18 kV and a negative voltage of -2 kV, with a product collection distance of 10 cm, to obtain a fiber membrane with a thickness of 900 μm. The collected fiber membrane was then carbonized at 600℃ for 16 hours in a high-purity argon atmosphere rich in tellurium powder (heating rate 2℃ / min) to obtain a zirconium-based flexible carbon nanofiber membrane with zirconium telluride (Te₂Zr) as the active site.

[0087] The obtained zirconium-based flexible carbon nanofiber membrane was cut into circular models of equal size (14 mm in diameter) to serve as membrane reactors, with a sulfur surface loading of 8 mg / cm³. 2 Using ordinary sulfur cathodes, a novel "sandwich" sulfur cathode is constructed and assembled with commercial electrolytes, separators, and lithium sheets to form coin-type lithium-sulfur batteries.

[0088] Figure 6 The graph shows the cycle performance test results of the assembled coin-type lithium-sulfur battery. Figure 6 It can be seen that this lithium-sulfur battery achieves high-capacity cycling at a rate of 0.1C.

[0089] The resulting coin cell lithium-sulfur battery has an areal load of 8 mg / cm³. 2 It has a specific capacity of 1087.5 mAh / g and an areal capacity of 8.7 mAh / cm². 2 .

[0090] Example 5

[0091] 5 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.2 g of polyvinylpyrrolidone, and 0.6 g of polystyrene were dissolved together in a 50 mL beaker and stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun under conditions of ≤30% RH and 20℃, using a positive voltage of 18 kV and a negative voltage of -2 kV, with a product collection distance of 8 cm, to obtain a fiber membrane with a thickness of 1200 μm. The collected fiber membrane was then carbonized at 1100℃ for 3 hours under a high-purity nitrogen atmosphere (heating rate of 5℃ / min) to obtain a zirconium-based flexible carbon nanofiber membrane with zirconium dioxide (ZrO2) as the active site.

[0092] The obtained zirconium-based flexible carbon nanofiber membrane was cut into rectangular models of equal size (5cm × 8cm) to serve as membrane reactors, with a sulfur surface loading of 6 mg / cm³. 2 Using ordinary sulfur cathodes, a novel "sandwich" sulfur cathode is constructed and assembled with commercial electrolytes, separators, and lithium sheets to create soft-pack lithium-sulfur batteries.

[0093] The resulting coin cell lithium-sulfur battery has an areal load of 6 mg / cm³. 2 It has a specific capacity of 1016.7 mAh / g and an areal capacity of 6.1 mAh / cm³. 2 .

[0094] Example 6

[0095] 3 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.0 g of polyvinylpyrrolidone, and 0.5 g of polystyrene were dissolved together in a 50 mL beaker and stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun under conditions of ≤30% RH and 20℃, using a positive voltage of 18 kV and a negative voltage of -2 kV, with a product collection distance of 10 cm, to obtain a fiber membrane with a thickness of 1500 μm. The collected fiber membrane was then carbonized at 1000℃ for 3 hours in a high-purity ammonia atmosphere (heating rate of 6℃ / min) to obtain a zirconium-based flexible carbon nanofiber membrane with zirconium nitride (ZrN) as the active site.

[0096] The obtained zirconium-based flexible carbon nanofiber membrane was cut into rectangular models of equal size (20cm × 5cm) and circular models with a diameter of 12mm to serve as membrane reactors, with a sulfur surface loading of 10mg / cm³. 2 Using ordinary sulfur cathodes, a novel "sandwich" sulfur cathode is constructed, which is then combined with commercial electrolytes, separators, and lithium sheets to assemble cylindrical and button lithium-sulfur batteries.

[0097] Figure 7 The graph shows the cycle performance test results of the assembled coin-type lithium-sulfur battery. Figure 7 It can be seen that this lithium-sulfur battery achieves high-capacity cycling at a rate of 0.1C.

[0098] The resulting coin cell lithium-sulfur battery has an areal load of 10 mg / cm³. 2 The specific capacity is 1010.1 mAh / g, and the areal capacity is 10.1 mAh / cm². 2 .

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lithium-sulfur battery, characterized in that, Includes positive electrode, lithium negative electrode, electrolyte and separator; The positive electrode is the positive electrode of a lithium-sulfur battery; The lithium-sulfur battery cathode comprises a first membrane reactor, a sulfur cathode, and a second membrane reactor stacked together; the first and second membrane reactors are zirconium-based flexible carbon nanofiber membranes; the sulfur cathode is a conventional sulfur cathode, which is an electrode formed by grinding and coating an activated carbon / sulfur composite material; the sulfur surface loading of the conventional sulfur cathode is ≥6 mg / cm³. 2 ; The preparation method of the zirconium-based flexible carbon nanofiber membrane includes the following steps: 3 mL of tetrabutyl zirconate, 10 mL of N-methylpyrrolidone, 1.0 g of polyvinylpyrrolidone, and 0.5 g of polystyrene were dissolved together in a 50 mL beaker. Then, 1 g of selenium (Se) powder was added and the mixture was stirred for 8 hours to obtain a spinning solution. The spinning solution was electrospun in an environment with humidity ≤30%RH and temperature of 20℃, using a positive voltage of 18KV and a negative voltage of -2KV, with a product collection distance of 10 cm to obtain a fiber membrane with a thickness of 800 micrometers. The collected fiber membranes were carbonized at 600°C for 16 hours in a high-purity argon atmosphere with a heating rate of 2°C / min to obtain zirconium-based flexible carbon nanofiber membranes with zirconium selenide as the active site.

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