Preparation method of MXene molybdenum telluride nano composite material, modified diaphragm as well as preparation method and application of modified diaphragm

Abstract

The invention provides a preparation method of an MXene molybdenum telluride nano composite material, a modified diaphragm as well as a preparation method and application of the modified diaphragm, and relates to the technical field of batteries. According to the invention, a composite structure of 2H-MoTe2 nanoparticles and MX nanosheets is constructed by adopting an electrostatic self-assembly method, and the composite structure is used as a modified material of a lithium battery diaphragm. Research finds that the prepared modified diaphragm not only can effectively adsorb soluble lithium polysulfide and prevent the shuttle effect, but also can improve the reversibility of the reaction and promote the kinetic process of the oxidation-reduction reaction by accelerating the deposition and dissolution speed of sulfur species in the lithium-sulfur battery. The adsorption catalytic effect brought by the unique change of the energy band structure provides important guidance for the next generation of commercial long-cycle-life lithium-sulfur battery.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a preparation method of a MXene molybdenum telluride nanocomposite material, a modified diaphragm, and a preparation method and application thereof. Background Art

[0002] In recent years, with the surge in demand in the energy industry, traditional energy storage devices have been unable to meet the growing market demand due to low energy density, poor cycle retention, and high cost. People are eager for the emergence of more diverse energy storage devices. Lithium-sulfur batteries stand out for their high energy density (2600Wh kg-1), low cost, and environmental friendliness. Despite these advantages, the large-scale commercialization of lithium-sulfur batteries still faces many challenges. For example, the insulation of sulfur, the large barrier required for Li2S dissolution, and the shuttle effect caused by soluble lithium polysulfides. Severe shuttle effects can cause soluble lithium polysulfides to diffuse to the lithium anode and deposit on the lithium metal surface, resulting in the loss of active sulfur. In addition, slow sulfur redox reactions are also a key issue limiting the performance of lithium-sulfur batteries.

[0003] To address these challenges and expand the commercial application of lithium-sulfur batteries, researchers have made significant efforts. For example, Wu et al. reported using nitrogen-doped carbon materials as substrates for the sulfur cathode in lithium-sulfur batteries, leveraging their large surface area to achieve sufficient contact with the active sulfur. The nitrogen-doped sites enhance the overall material's adsorption capacity for soluble lithium polysulfides, effectively suppressing the shuttle effect and improving material utilization. In addition to optimizing the sulfur cathode, separator modification offers another facile approach to achieving these goals. The prepared modified material is coated on the surface of the separator used in battery assembly. Soluble lithium polysulfides diffuse onto the separator surface and are captured by the modified material. Sulfur species are then redistributed on the separator surface, undergoing redox reactions. This separator modification not only significantly improves material utilization but also fully utilizes the modified material's adsorption and catalytic properties, effectively promoting the device's redox kinetics. Therefore, finding suitable separator modification materials is a crucial task in improving the performance of lithium-sulfur batteries.

[0004] In recent years, transition metal tellurium, such as TiS2, VS2, CoS2, and NiCo2S4, has been demonstrated to possess strong adsorption and catalytic properties for soluble lithium polysulfides as separator-modified materials for lithium-sulfur batteries. Among them, the non-metallic phase MoTe2 (2H-MoTe2) has attracted considerable attention due to its strong binding affinity with soluble lithium polysulfides, environmental friendliness, and commercial viability. For example, Chen et al. reported the application of a separator modified with acetylene black and cobalt disulfide complex (AB-CoS2) in lithium-sulfur batteries, demonstrating excellent adsorption and catalytic activity. Lithium-sulfur batteries using the AB-CoS2 separator exhibited excellent rate performance (475 mAh g-1 at a current density of 4C) and good cycling stability. However, the band structure of 2H-MoTe2 reveals a large gap between its conduction and valence bands. This large band gap hinders rapid electron transfer, thereby limiting the catalytic performance of 2H-MoTe2 in adsorbing soluble lithium polysulfides. Furthermore, transition metal tellurium catalysts often aggregate and disintegrate during charge and discharge, a serious issue for 2H-MoTe2 as a separator modification material for lithium-sulfur batteries. An effective strategy to address this issue is to assemble transition metal tellurium onto a highly conductive two-dimensional network to form a composite structure. The presence of the composite structure improves the stability of the transition metal tellurium, modifies its energy band structure, and promotes electron transfer. The rapid electron transfer further enhances the adsorption and catalytic ability of the transition metal tellurium. MXene (MX) is a novel two-dimensional transition metal carbon / nitride. Its excellent conductivity, large specific surface area, and abundant surface functional groups provide favorable binding conditions for transition metal tellurium. For example, Yang et al. reported a sulfur cathode modification based on Fe2O3 / MX and demonstrated the influence of the composite structure on the adsorption and catalytic performance. Therefore, the preparation of MX-transition metal tellurium composites and the design of their composite structure have become important topics for the large-scale commercial application of lithium-sulfur batteries.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a method for preparing a MXene molybdenum telluride nanocomposite material.

[0007] A second object of the present invention is to provide a modified separator.

[0008] The third object of the present invention is to provide a method for preparing the modified diaphragm.

[0009] A fourth object of the present invention is to provide application of the modified separator in lithium-sulfur batteries.

[0010] In order to achieve the above objectives, the following technical solutions are adopted:

[0011] In a first aspect, the present invention provides a method for preparing a MXene molybdenum telluride nanocomposite material, comprising the following steps:

[0012] a. Dispersed MXene and (NH4)6Mo7O 24 Adding poly(oxypropylene) diamine to the aqueous solution to carry out a hydrothermal reaction, and then freeze-drying the material obtained by the reaction to obtain a precursor material;

[0013] b. Tellurium is placed upstream of a tube furnace, and the precursor material is placed downstream of the tube furnace. A protective gas is then introduced and the mixture is treated at 500°C-1000°C to prepare a MXene molybdenum telluride nanocomposite material.

[0014] The MXene is a thin layer of Ti3C2T x .

[0015] As a further technical solution, the temperature of the hydrothermal reaction is 50°C-100°C.

[0016] As a further technical solution, in the MXene molybdenum telluride nanocomposite material, the mass ratio of MXene to molybdenum telluride is 0.25-1.25.

[0017] As a further technical solution, the thin layer Ti3C2T x The preparation method comprises the following steps:

[0018] LiF and hydrochloric acid aqueous solution were mixed, and then Ti3AlC2 was added for etching reaction. After that, the reacted material was washed with water to a pH of above 6, and then ultrasonic dispersion and centrifugation were performed to remove the multilayer Ti3C2T x and freeze-dried to obtain thin Ti3C2T x .

[0019] In a second aspect, the present invention provides a modified diaphragm, comprising a base film and a modified layer disposed on a surface of the base film;

[0020] The modified layer includes a MXene molybdenum telluride nanocomposite material prepared by the preparation method.

[0021] As a further technical solution, the base film includes a PP diaphragm.

[0022] As a further technical solution, the density of the MXene molybdenum telluride nanocomposite material in the modified layer is 0.1 mg / cm 2 -5 mg / cm 2 .

[0023] In a third aspect, the present invention provides a method for preparing the modified diaphragm, comprising the following steps:

[0024] The MXene molybdenum telluride nanocomposite material is dispersed in a solvent, and then a binder is added to obtain a modified liquid. The base membrane is then used as a filter membrane, and the modified liquid is added to the base membrane for filtration. After drying, a modified diaphragm is prepared.

[0025] As a further technical solution, the binder includes PVDF (polyvinylidene fluoride).

[0026] In a fourth aspect, the present invention provides use of the modified diaphragm in a lithium-sulfur battery.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention uses an electrostatic self-assembly method to construct a composite structure of 2H-MoTe2 nanoparticles and MX nanosheets, and uses it as a modified material for lithium battery separators (MX@MoTe2 / PP). As the main modified material for the separator, the MX nanosheets can not only effectively block the diffusion of soluble lithium polysulfides, but also prevent the aggregation and disintegration of 2H-MoTe2 nanoparticles during the conversion process of soluble lithium polysulfides. In addition, the formation of the composite structure changes the outer band structure of 2H-MoTe2, which is due to the addition of multiple doping levels of MX between the band gap of 2H-MoTe2. The emergence of doping energy levels changes electron transfer from a difficult one-step transfer to a staged transfer, making electron transfer smoother and faster. The change in the band structure not only makes the composite material exhibit strong adsorption for soluble lithium polysulfides, but also improves the deposition and dissolution rate of Li2S. It is worth noting that this promoting effect is bidirectional, not only reducing the decomposition barrier of Li2S during the oxidation process, but also accelerating the rate-controlling step in the reduction process. Therefore, MX@MoTe2 / PP not only effectively adsorbs soluble lithium polysulfides and prevents the shuttle effect, but also accelerates the deposition and dissolution of sulfur species in lithium-sulfur batteries, improving the reversibility of the reaction and promoting the kinetics of the redox reaction. The adsorption-catalytic effect brought about by the unique changes in the band structure provides important guidance for the next generation of commercial lithium-sulfur batteries with long cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1:ac) SEM images of MX; de) TEM image of MX@MoTe2; f) HRTEM image of MX@MoTe2; gk) HAADF-STEM image of MX@MoTe2 and corresponding EDS elemental maps;

[0031] Figure 2 : XRD patterns of MoTe2 and MX@MoTe2;

[0032] Figure 3 : Raman spectra of MX, MoTe2 and MX@MoTe2;

[0033] Figure 4 :a) Cycling performance of lithium-sulfur batteries based on different separators at 0.1C; b) Rate performance of different separators;

[0034] Figure 5 :Static charge-discharge curves of lithium-sulfur batteries based on MX@MoTe2 / PP separator at different current densities;

[0035] Figure 6 :Long cycle performance of lithium-sulfur batteries based on MX@MoTe2 / PP separator at 5C;

[0036] Figure 7 : Cycling performance of lithium-sulfur batteries based on MX@MoTe2 / PP separator under high sulfur loading and low electrolyte / sulfur ratio conditions. DETAILED DESCRIPTION

[0037] Below in conjunction with embodiment and example, embodiment of the present invention is described in detail, but those skilled in the art will appreciate that the following embodiment and example are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. Unspecified conditions are carried out according to the conditions of normal conditions or manufacturer's recommendations. Reagents used or instruments not specified by the manufacturer are conventional products that can be purchased commercially.

[0038] In a first aspect, the present invention provides a method for preparing a MXene molybdenum telluride nanocomposite material, comprising the following steps:

[0039] a. Dispersed MXene and (NH4)6Mo7O 24 Adding poly(oxypropylene) diamine to the aqueous solution to carry out a hydrothermal reaction, and then freeze-drying the material obtained by the reaction to obtain a precursor material;

[0040] b. Tellurium is placed upstream of a tube furnace, and the precursor material is placed downstream of the tube furnace. A protective gas is then introduced and the mixture is treated at 500°C-1000°C to prepare a MXene molybdenum telluride nanocomposite material.

[0041] The MXene is a thin layer of Ti3C2T x .

[0042] The preparation method is simple and convenient.

[0043] In some optional embodiments, the temperature of the hydrothermal reaction is 50° C.-100° C., and the time can be, for example, 1 minute.

[0044] In some optional embodiments, in the MXene molybdenum telluride nanocomposite material, the mass ratio of MXene to molybdenum telluride is 0.25-1.25, preferably 0.75.

[0045] In some optional embodiments, the thin layer Ti3C2T x The preparation method comprises the following steps:

[0046] LiF and hydrochloric acid aqueous solution were mixed, and then Ti3AlC2 was added for etching reaction. After that, the reacted material was washed with water to a pH of above 6, and then ultrasonic dispersion and centrifugation were performed to remove the multilayer Ti3C2T x and freeze-dried to obtain thin Ti3C2T x .

[0047] In some optional embodiments, the amount of LiF is 0.1g-5g; the concentration of hydrochloric acid is 0.1M-12M; while ensuring sufficient etching, the amount of Ti3AlC2 is 0.1-10g; the temperature of the etching reaction is 0-100°C, and the time is 1-100h.

[0048] In some optional embodiments, the centrifugal speed is 3500 r / min and the time is 1 h. Centrifugation under this condition can fully precipitate multilayer Ti3C2T x , to obtain a single layer or thin layer of Ti3C2T x .

[0049] In a second aspect, the present invention provides a modified diaphragm, comprising a base film and a modified layer disposed on a surface of the base film;

[0050] The modified layer includes a MXene molybdenum telluride nanocomposite material prepared by the preparation method.

[0051] The modified diaphragm provided by the present invention can not only effectively adsorb soluble lithium polysulfide and prevent the shuttle effect, but also accelerate the deposition and dissolution rate of sulfur species in lithium-sulfur batteries, improve the reversibility of the reaction, and promote the kinetic process of the redox reaction.

[0052] In some optional embodiments, the base film includes but is not limited to a PP separator.

[0053] In some optional embodiments, the density of the MXene molybdenum telluride nanocomposite material in the modified layer is 0.1 mg / cm 2 -5 mg / cm 2 .

[0054] In a third aspect, the present invention provides a method for preparing the modified diaphragm, comprising the following steps:

[0055] The MXene molybdenum telluride nanocomposite material is dispersed in a solvent, and then a binder is added to obtain a modified liquid. The base membrane is then used as a filter membrane, and the modified liquid is added to the base membrane for filtration. After drying, a modified diaphragm is prepared.

[0056] In some optional embodiments, the binder includes but is not limited to PVDF, or other binders well known to those skilled in the art.

[0057] In a fourth aspect, the present invention provides use of the modified diaphragm in a lithium-sulfur battery.

[0058] The present invention is further described below by means of specific examples and comparative examples. However, it should be understood that these examples are merely provided for more detailed description and are not to be construed as limiting the present invention in any form.

[0059] Example 1

[0060] The preparation method of MXene molybdenum telluride nanocomposite material comprises the following steps:

[0061] Preparation of Ti3C2T x Nanosheets (MX nanosheets): Dissolve 0.8 g of LiF powder in 9 M HCl and stir for 20 minutes. Slowly add 1 g of Ti3AlC2 powder to the solution and stir for 30 minutes. Heat the mixture to 35°C for 48 hours. Wash with deionized water until the pH reaches 6. Ultrasonicate under argon for 75 minutes, then centrifuge at 3500 rpm for 1 hour. Collect the supernatant and freeze-dry.

[0062] Preparation of MX@MoTe2: First, (NH4)6Mo7O 24 4H2O (200mg) added 30mL 3mg mL -1MX solution, and then the mixture was ultrasonicated for 1 hour. Subsequently, 0.3 g of poly (oxypropylene) diamine (D-400) was dissolved in the aqueous dispersion and heated to 90 ° C for 1 minute. The resulting material was freeze-dried. Then, tellurium (Te) was placed upstream of the tube furnace and the previously obtained sample was placed downstream (8 cm from the upstream). Then 50 sccm of argon was introduced into the tube and heated to 700 ° C (5 ° C min -1 ) and kept for 2 hours to obtain MX@MoTe2, where the mass ratio of MXene to molybdenum telluride is 0.75.

[0063] Example 2

[0064] The preparation method of MXene molybdenum telluride nanocomposite material comprises the following steps:

[0065] Preparation of Ti3C2T x Nanosheets: Dissolve 0.8 g of LiF powder in 9 M HCl and stir for 20 minutes. Slowly add 1 g of Ti3AlC2 powder to the solution and stir for 30 minutes. Heat the mixture to 35°C for 48 hours. Wash with deionized water until the pH reaches 6. Ultrasonicate under argon for 75 minutes, then centrifuge at 3500 rpm for 1 hour. Collect the supernatant and freeze-dry.

[0066] Preparation of MX@MoTe2: First, (NH4)6Mo7O 24 4H2O (200mg) added 30mL 3mg mL -1 MX solution, and then the mixture was ultrasonicated for 1 hour. Subsequently, 0.3 g of poly (oxypropylene) diamine (D-400) was dissolved in the aqueous dispersion and heated to 50 ° C for 1 minute. The resulting material was freeze-dried. Then, tellurium (Te) was placed upstream of the tube furnace and the previously obtained sample was placed downstream (8 cm from the upstream). Then 50 sccm of argon was introduced into the tube and heated to 500 ° C (5 ° C min -1 ) and kept for 2 hours to obtain MX@MoTe2, where the mass ratio of MXene to molybdenum telluride is 0.25.

[0067] Example 3

[0068] The preparation method of MXene molybdenum telluride nanocomposite material comprises the following steps:

[0069] Preparation of Ti3C2T xNanosheets: Dissolve 0.8 g of LiF powder in 9 M HCl and stir for 20 minutes. Slowly add 1 g of Ti3AlC2 powder to the solution and stir for 30 minutes. Heat the mixture to 35°C for 48 hours. Wash with deionized water until the pH reaches 6. Ultrasonicate under argon for 75 minutes, then centrifuge at 3500 rpm for 1 hour. Collect the supernatant and freeze-dry.

[0070] Preparation of MX@MoTe2: First, (NH4)6Mo7O 24 4H2O (200mg) added 30mL 3mg mL -1 MX solution, and then the mixture was ultrasonicated for 1 hour. Subsequently, 0.3 g of poly (oxypropylene) diamine (D-400) was dissolved in the aqueous dispersion and heated to 100 ° C for 1 minute. The resulting material was freeze-dried. Then, tellurium (Te) was placed upstream of the tube furnace and the previously obtained sample was placed downstream (8 cm from the upstream). Then 50 sccm of argon was introduced into the tube and heated to 1000 ° C (5 ° C min -1 ) and kept for 2 hours to obtain MX@MoTe2, where the mass ratio of MXene to molybdenum telluride is 1.25.

[0071] Comparative Example 1

[0072] MoTe2, the preparation method thereof is different from that of Example 1 in that no MXene is added.

[0073] Comparative Example 2

[0074] MX-MoTe2 is prepared as follows: Ti3C2T x The nanosheets and the MoTe2 of Comparative Example 1 were dispersed in water at a mass ratio of 0.75, and MX-MoTe2 was obtained after freeze-drying.

[0075] Example 4

[0076] A modified diaphragm includes a PP base film and a modified layer disposed on the surface of the base film. The preparation method is as follows:

[0077] 10 mg of MX@MoTe2 of Example 1 was added to 20 mL of isopropanol and ultrasonically treated for 30 minutes, and then 0.2 mL of binder solution (PVDF dissolved in NMP, mass fraction of 2.5%) was added and ultrasonically treated for 30 minutes. The mixed solution was filtered on a Celgard 2400 diaphragm with a vacuum filtration device and dried at 60 ° C under vacuum conditions for 8 hours. The dried sample was cut into a diaphragm with a diameter of 19 mm. Among them, the density of the MXene molybdenum telluride nanocomposite material in the modified layer is 0.1 mg / cm 2 .

[0078] Example 5

[0079] The difference from Example 4 is that the MX@MoTe2 of Example 2 is used for preparation, and the density of the MXene molybdenum telluride nanocomposite material in the modified layer of the prepared modified membrane is 5 mg / cm 2 .

[0080] Example 6

[0081] The difference from Example 4 is that the MX@MoTe2 of Example 3 is used for preparation, and the density of the MXene molybdenum telluride nanocomposite material in the modified layer of the prepared modified diaphragm is 3 mg / cm 2 .

[0082] Comparative Example 3

[0083] The difference from Example 4 is that the MoTe2 of Comparative Example 1 is used for preparation.

[0084] Comparative Example 4

[0085] The difference from Example 4 is that the MX-MoTe2 of Comparative Example 2 is used for preparation.

[0086] Comparative Example 5

[0087] The difference from Example 4 is that the Ti3C2T prepared in Example 1 is used. x Nanosheets were prepared.

[0088] Test Example 1

[0089] The above-mentioned diaphragms were used to prepare lithium-sulfur batteries according to the same preparation process. The preparation method of the sulfur cathode of the lithium-sulfur battery is as follows:

[0090] S powder and Ketjen Black (KB) were mixed in a weight ratio of 8:2 and sealed in a Teflon container filled with argon. The mixture was then heated to 155°C in an oven for 12 hours. S / KB and a water-based binder (LA132) were mixed in a weight ratio of 9:1, coated on aluminum foil, and dried in a vacuum at 60°C for 12 hours. The electrodes were cut into 12 mm wafers, with a sulfur loading of 1.2 mg cm per wafer. -2 .

[0091] The electrolyte is: solvent (dimethyl ether (DME): 1,3-dioxolane (DOL) = 1:1 (volume ratio)), 1M LiTFSI, 2.0wt% LiNO3, and the standard injection volume of each button cell is 40μL.

[0092] The Ti3C2T prepared in Example 1 and Example 1 xThe performance of the lithium-sulfur batteries prepared from the nanosheets and comparative examples 1-2, as well as example 4 and comparative examples 3-5 were tested, and the results were as follows:

[0093] The morphology and microstructure of MX and MX@MoTe2 composites were characterized by scanning electron microscopy and transmission electron microscopy, as shown in Figure 2. Figure 1 As shown in ae. Compared with pure MX nanosheets, 2H-MoTe2 nanosheets are uniformly distributed on the surface of MX@MoTe2. From high-resolution TEM (HRTEM), it can be observed that the lattice spacing is 0.156, 0.254 and 0.263 nm, respectively, corresponding to the (114) and (103) crystal planes of 2H-MoTe2 nanosheets and the (101) crystal plane of MX nanosheets ( Figure 1 f). This indicates that the MX nanosheets are successfully bonded to the 2H-MoTe2 nanosheets. High-angle annular dark-field scanning transmission microscopy (HAADF-STEM) Figure 1 The gk in Figure 3 shows that Ti, O, Mo, and Te are uniformly distributed on the surface of MX@MoTe2 nanosheets, further confirming the coexistence of 2H-MoTe2 and MX.

[0094] Figure 2 The X-ray diffraction patterns of MoTe2 and MX@MoTe2 composites are shown. As can be seen from the figure, in addition to the characteristic peak of MoTe2, the characteristic peak corresponding to MX nanosheets in the MX@MoTe2 composite appears at 19.7°.

[0095] In Raman spectroscopy test ( Figure 3 ), the MX nanosheet vibration mode of 176.5cm also appeared in the MX@MoTe2 composite material. -1 peaks at 138.2 and 249.1 cm-1 of the vibration modes of MoTe2 nanoparticles -1 This indicates the successful preparation of MX@MoTe2 composite materials.

[0096] The MX@MoTe2 modified separator not only greatly improves the reversibility and reaction kinetics of the lithium-S battery, but also further enhances the diffusion of ions in the active material due to its excellent adsorption and catalytic properties for soluble lithium polysulfide. This makes the lithium-S battery equipped with the MX@MoTe2 modified separator exhibit excellent electrochemical performance. It can be seen that in the current static charge and discharge test conducted on the LAND battery tester, compared with MX-MoTe2 / PP and MoTe2 / PP, the lithium-sulfur battery using MX@MoTe2 / PP has a specific capacity of up to 1638.3mAh g at a current density of 0.1C. -1 , and can still maintain 1049.6mAh g after 100 cycles -1 ( Figure 4 a). This is because the MX@MoTe2 composite material has a strong adsorption capacity for soluble lithium polysulfide, which significantly improves the utilization rate of the active material. Subsequently, the rate performance test was carried out (test method: current static charge and discharge test was carried out on a battery tester with a voltage range of 1.7-2.8V.). Figure 4 As shown in (b), the specific capacities of the lithium-sulfur battery equipped with the MX@MoTe2 modified separator are 1380.1, 1179.4, 1066.6, 930.4, 826.4, 736, 657, and 9 mAh g at current densities of 0.1, 0.2, 0.5, 1, 2, 3, 4, and 5 C, respectively. -1 When the current density returned to 0.1C, the specific capacity was 1227.5 mAh g -1 In contrast, lithium-sulfur batteries equipped with other modified separators cannot effectively suppress the shuttle effect of soluble lithium polysulfides at high current density, so the capacity is greatly reduced and cannot work properly. Figure 5 The charge and discharge curves at different current densities are shown. It can be seen that even at a high current density of 5C, the lithium-S battery equipped with MX@MoTe2 / PP can still maintain a good charge and discharge curve shape. This is due to the strong adsorption and catalytic properties of the MX@MoTe2 composite material on soluble lithium polysulfide, which enables it to achieve high-speed conversion of soluble lithium polysulfide when used as a modified separator for lithium-sulfur batteries. Figure 6 As shown, the lithium-sulfur battery loaded with MX@MoTe2 / PP was cycled 1000 times at a high current density of 5C with a capacity decay of only 0.021% per cycle.

[0097] In addition, a "high sulfur load" lithium-sulfur battery and a "poor electrolyte / sulfur" lithium-sulfur battery were prepared using the modified diaphragm provided in Example 4. The difference between the "high sulfur load" lithium-sulfur battery and the aforementioned preparation method lies in the different preparation method of the sulfur cathode, which is as follows:

[0098] S powder and Ketjen Black (8:2 weight ratio) were mixed and sealed in a Teflon container filled with argon and then heated to 155°C in an oven for 12 hours. S / KB and a water-based binder (LA132) were mixed in an 80:1 weight ratio, coated on aluminum foil, and dried in a vacuum at 60°C for 12 hours. The electrode was cut into 12 mm wafers, with a sulfur loading of 9.34 mg cm per wafer. -2 .

[0099] The difference between the "poor electrolyte / sulfur" lithium-sulfur battery and the aforementioned preparation method is that the injection volume is reduced to 20μL.

[0100] The cycling performance of lithium-sulfur batteries under high sulfur loading and poor electrolyte / sulfur (E / S) conditions was evaluated using the LAND battery tester ( Figure 7 The results show that even at high sulfur loading (9.34 mg cm -2 ) and lean electrolyte / sulfur (6.0 μL mg -1 ) condition, the lithium-sulfur battery loaded with MX@MoTe2 / PP still showed 768.5mAh g -1 High specific capacity and 7.18 mAh cm -2 Its areal capacity is the highest among commercial lithium-ion batteries (4 mAh cm -2 ), which has important guiding significance for the commercialization of lithium-ion batteries.

[0101] In addition, the lithium-sulfur battery equipped with the MX@MoTe2 modified separator of Example 5 was tested on a LAND battery tester for static charge and discharge. The specific capacity was 690.2, 588.6, 510.1, 442.1, 331.5.4, 250.6, 10 and 4 mAh g at current densities of 0.1, 0.2, 0.5, 1, 2, 3, 4 and 5 C, respectively. -1 .

[0102] The lithium-sulfur battery equipped with the MX@MoTe2 modified separator of Example 6 was subjected to static current charge and discharge tests on a LAND battery tester. The specific capacities were 1001.2, 875.2, 778.9, 642.3, 465.4, 376.3, 202.2 and 7 mAh g at current densities of 0.1, 0.2, 0.5, 1, 2, 3, 4 and 5 C, respectively. -1 Examples 5 and 6 also achieved good technical effects.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a MXene molybdenum telluride nanocomposite material, characterized in that: The following steps are involved: a. Dispersed MXene and (NH4)6Mo7O 24 Adding poly(oxypropylene) diamine to the aqueous solution to carry out a hydrothermal reaction, and then freeze-drying the material obtained by the reaction to obtain a precursor material; b. Tellurium is placed upstream of a tube furnace, and the precursor material is placed downstream of the tube furnace. A protective gas is then introduced and the mixture is treated at 500°C-1000°C to prepare a MXene molybdenum telluride nanocomposite material. The MXene is a thin layer of Ti3C2T x .

2. The preparation method according to claim 1, characterized in that The temperature of the hydrothermal reaction is 50°C-100°C.

3. The preparation method according to claim 1, characterized in that In the MXene molybdenum telluride nanocomposite material, the mass ratio of MXene to molybdenum telluride is 0.25-1.

25.

4. The preparation method according to claim 1, characterized in that The thin layer Ti3C2T x The preparation method comprises the following steps: LiF and hydrochloric acid aqueous solution were mixed, and then Ti3AlC2 was added for etching reaction. After that, the reacted material was washed with water to a pH of above 6, and then ultrasonic dispersion and centrifugation were performed to remove the multilayer Ti3C2T x and freeze-dried to obtain thin Ti3C2T x .

5. A modified diaphragm, characterized in that: It includes a base film and a modified layer arranged on the surface of the base film; The modified layer comprises a MXene molybdenum telluride nanocomposite material prepared by the preparation method according to any one of claims 1 to 4.

6. The modified diaphragm according to claim 5, characterized in that The base film includes a PP separator.

7. The modified diaphragm according to claim 5, characterized in that The density of the MXene molybdenum telluride nanocomposite material in the modified layer is 0.1 mg / cm 2 -5 mg / cm 2 .

8. The method for preparing the modified diaphragm according to any one of claims 5 to 7, characterized in that: The following steps are involved: The MXene molybdenum telluride nanocomposite material is dispersed in a solvent, and then a binder is added to obtain a modified liquid. The base membrane is then used as a filter membrane, and the modified liquid is added to the base membrane for filtration. After drying, a modified diaphragm is prepared.

9. The preparation method according to claim 8, characterized in that The binder includes PVDF.

10. Use of the modified separator according to any one of claims 5 to 7 in a lithium-sulfur battery.

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