Application of MoS2-Mo2C MXene composite in preparation of lithium-sulfur battery separator

Abstract

The application belongs to the technical field of lithium-sulfur batteries, and provides application of a MoS2-Mo2C MXene composite material in preparation of a lithium-sulfur battery diaphragm, which comprises the following steps: heating and stirring etching of a Mo2Ga2C MAX material in hydrofluoric acid to obtain Mo2C MXene powder A; dissolving ammonium molybdate, glucose and thiourea in water to form a solution A, and adding the Mo2C MXene powder A; hydrothermal treatment of the precursor product, water washing until neutral, freeze-drying to obtain a precursor powder B; calcining the powder B to obtain a MoS2-Mo2C MXene composite material; and adjusting the composite material into a slurry to modify the surface of the diaphragm, so as to obtain a modified lithium-sulfur battery diaphragm. The application reduces polysulfide dissolution and shuttling, the MoS2-Mo2C MXene composite material acts as an electrocatalyst to promote the conversion of polysulfides in the battery charging and discharging process, accelerates the reaction kinetics, and improves the cycle stability and rate performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur battery technology, and particularly relates to the application of MoS2-Mo2C MXene composite material in the preparation of lithium-sulfur battery separators. Background Technology

[0002] With the rapid development of electric vehicles and various electronic products, the demand for high-energy-density energy storage systems is constantly increasing. Lithium-sulfur batteries, due to their high theoretical specific capacity (1675 mA g), are particularly valuable. -1 Its advantages, such as high energy density (2600 Wh / kg), low cost, and environmental friendliness, have led to extensive research and made it a strong contender for the next generation of rechargeable batteries.

[0003] Currently, the main problems that need to be solved for the commercial application of lithium-sulfur batteries include two aspects: (1) the low conductivity of sulfur and polysulfides during battery charging and discharging, resulting in poor rate performance. (2) the polysulfide shuttle effect, where polysulfides formed during the battery reaction dissolve in the electrolyte and shuttle through the separator to the lithium metal anode to react with lithium metal, resulting in low coulombic efficiency and irreversible capacity loss. In addition, the slow conversion rate of polysulfides leads to a decrease in battery cycle and rate performance. Therefore, developing highly conductive materials and integrating electrocatalysts as separator modifiers to achieve polysulfide adsorption and accelerate reaction kinetics is expected to promote the commercial application of lithium-sulfur batteries. To this end, we propose the application of MoS2-Mo2C MXene composite material in the preparation of lithium-sulfur battery separators. Summary of the Invention

[0004] The purpose of this invention is to provide the application of MoS2-Mo2C MXene composite material in the preparation of lithium-sulfur battery separators, aiming to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The application of MoS2-Mo2C MXene composite material in the preparation of lithium-sulfur battery separators, wherein the MoS2-Mo2C MXene composite material is prepared by the following method:

[0007] Step S1: Preparation of Mo2C MXene: Mo2Ga2C MAX material is slowly added to hydrofluoric acid solution, heated and stirred in a polytetrafluoroethylene liner, and etched to obtain Mo2C MXene powder A;

[0008] Step S2: Dissolve molybdate, glucose and sulfur source in water to form a homogeneous solution A;

[0009] Step S3: Add powder A to solution A, and after hydrothermal treatment, obtain the precursor product;

[0010] Step S4: Wash the precursor product with water until neutral, and freeze-dry to obtain precursor powder B;

[0011] Step S5: Calcine the obtained powder B in argon to obtain the MoS2-Mo2C MXene composite material.

[0012] Furthermore, in step S1, the amount of Mo2Ga2C MAX material is 2-3 grams, the amount of hydrofluoric acid is 80-100 ml, the heating temperature is 55-60℃, and the etching time is 5-6 days.

[0013] Furthermore, in step S2, the molybdate is one of ammonium molybdate and sodium molybdate, the sulfur source is one of thiourea and thioacetamide, and the stirring time is 0.5-1 hour.

[0014] Furthermore, in step S2, the amount of ammonium molybdate is 300-600 mg, the amount of thiourea is 770-1540 mg, and the amount of glucose is 124-248 mg.

[0015] Furthermore, in step S3, the Mo2C Mxene powder is 50-100 mg, the stirring time is 0.5-1 hour, the hydrothermal temperature is 180-200℃, and the reaction time is 18-24 hours.

[0016] Furthermore, in step S4, the freeze-drying time is 1-2 days.

[0017] Furthermore, in step S5, the calcination temperature is 400-600ºC and the calcination time is 1-2 hours.

[0018] The lithium-sulfur battery separator is prepared by the following method:

[0019] MoS2-Mo2C MXene composite material and conductive carbon were mixed and ground evenly. The binder was dissolved in an organic solvent. The evenly ground material was added to the organic solvent containing the binder to form a slurry, which was then applied to the surface of the separator. The mixture was then vacuum dried to obtain the MoS2-Mo2C MXene modified lithium-sulfur battery separator.

[0020] Furthermore, the conductive carbon is one of Super P and acetylene black, and the binder is polyvinylidene fluoride (PVDF); the weight percentage of the MoS2-Mo2C MXene composite material is 70-80%, the weight percentage of the conductive carbon is 10-20%, and the weight percentage of the binder is 10%; the drying temperature is 50-60℃, and the thickness of the membrane coating is 30-60 micrometers.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The modified lithium-sulfur battery separator of this invention reduces polysulfide dissolution and shuttle. The MoS2-Mo2CMXene composite material acts as an electrocatalyst to promote polysulfide conversion during battery charging and discharging, accelerate reaction kinetics, and improve battery cycle stability and rate performance. Attached Figure Description

[0023] Figure 1 The images show the X-ray diffraction (XRD) patterns of the MoS2-Mo2C MXene composite material and the comparative material in Example 1.

[0024] Figure 2 : Figure 2 a is a scanning electron microscope (SEM) image of the Mo2C MXene composite material in Example 1. Figure 2 b is a scanning electron microscope image of the MoS2-Mo2C MXene composite material.

[0025] Figure 3 This is a cyclic volt-ampere curve of the symmetrical battery in Example 1.

[0026] Figure 4 This is a comparison chart of the cycling performance of the MoS2-Mo2C MXene composite material and the Mo2C MXene material at a current density of 1 C in Example 1.

[0027] Figure 5 This is a comparison chart of the rate performance of the MoS2-Mo2C MXene composite material and the Mo2C MXene material at different current densities in Example 1. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0030] An embodiment of the present invention provides the application of a MoS2-Mo2C MXene composite material in the preparation of lithium-sulfur battery separators. The MoS2-Mo2C MXene composite material is prepared by the following method:

[0031] Step S1: Preparation of Mo2C MXene: Hydrofluoric acid was added to 150 mL of polytetrafluoroethylene liner, and then a certain amount of Mo2Ga2C MAX material was slowly added to the hydrofluoric acid solution. The perforated liner was covered, heated and stirred, the product was centrifuged and washed with water until neutral, and vacuum dried to obtain Mo2C MXene powder A.

[0032] Step S2: Dissolve molybdate, glucose and sulfur source in water to form a homogeneous solution A;

[0033] Step S3: Add powder A to solution A, and after hydrothermal treatment, obtain the precursor product;

[0034] Step S4: Wash the precursor product with water until neutral, and freeze-dry to obtain precursor powder B;

[0035] Step S5: Calcine the obtained powder B in argon to obtain the MoS2-Mo2C MXene composite material.

[0036] In this embodiment of the invention, a MoS2-Mo2C MXene composite material with optimal performance was obtained by optimizing the feed ratio, reaction time, temperature, and other conditions. Mo2C MXene significantly improves the material's conductivity, which is beneficial for electron and ion transport. The heterostructure formed by MoS2 and Mo2C MXene provides a large number of active sites for the adsorption of polysulfides, reducing polysulfide dissolution and shuttle. MoS2 acts as an electrocatalyst to promote polysulfide conversion during battery charging and discharging, accelerates the uniform nucleation and deposition of Li2S, and speeds up reaction kinetics.

[0037] In a preferred embodiment of the present invention, in step S1, the amount of Mo2Ga2C MAX material is 2-3 grams, the amount of hydrofluoric acid is 80-100 ml, the heating temperature is 55-60°C, and the etching time is 5-6 days.

[0038] In a preferred embodiment of the present invention, in step S2, the molybdate is one of ammonium molybdate and sodium molybdate, the sulfur source is one of thiourea and thioacetamide, and the stirring time is 0.5-1 hour.

[0039] In a preferred embodiment of the present invention, in step S2, the amount of ammonium molybdate is 300-600 mg, the amount of thiourea is 770-1540 mg, and the amount of glucose is 124-248 mg.

[0040] In a preferred embodiment of the present invention, in step S3, the Mo2C MXene powder is 50-100 mg, the stirring time is 0.5-1 hour, the hydrothermal temperature is 180-200℃, and the reaction time is 18-24 hours.

[0041] In a preferred embodiment of the present invention, the freeze-drying time in step S4 is 1-2 days.

[0042] In a preferred embodiment of the present invention, in step S5, the calcination temperature is 400-600ºC and the calcination time is 1-2 hours.

[0043] The lithium-sulfur battery separator provided in one embodiment of the present invention is prepared by the following method:

[0044] MoS2-Mo2C MXene composite material and conductive carbon were mixed and ground evenly. The binder was dissolved in an organic solvent. The evenly ground material was added to the organic solvent containing the binder to form a slurry, which was then applied to the surface of the separator. The mixture was then vacuum dried to obtain the MoS2-Mo2C MXene modified lithium-sulfur battery separator.

[0045] In a preferred embodiment of the present invention, the conductive carbon is one of Super P and acetylene black, and the binder is polyvinylidene fluoride; the weight percentage of the MoS2-Mo2C MXene composite material is 70-80%, the weight percentage of the conductive carbon is 10-20%, and the weight percentage of the binder is 10%; the drying temperature is 50-60℃, and the thickness of the membrane coating is 30-60 micrometers.

[0046] In this embodiment of the invention, the battery assembly method is well known to those skilled in the art and is not included within the scope of protection of the claims of this invention. Detailed steps are as follows:

[0047] Sulfur cathode fabrication method: Multi-walled carbon nanotubes and sublimed sulfur are ground and mixed uniformly at a mass ratio of 7:3 for 0.5-1 hour. The uniformly ground powder is then loaded into a reaction vessel in a glove box and reacted in an oven at 155℃ for 24 hours to obtain a sulfur / carbon composite cathode material. The sulfur / carbon composite cathode material is mixed and ground uniformly with conductive carbon. A binder is dissolved in an organic solvent, and then the uniformly ground material is added to the organic solvent containing the binder and stirred uniformly to form a slurry. The slurry is uniformly coated onto commercial aluminum foil and vacuum dried at 60℃ for 24 hours. The dried aluminum foil is cut into 12 mm diameter discs as cathodes with a loading of 1-2 mg / cm³. -2 .

[0048] The negative electrode is a lithium metal sheet with a diameter of 15.6 mm.

[0049] Battery casing: CR2032

[0050] Electrolyte: 1 M LiTFSI, DOL / DME (volume ratio 1:1), 1.0 wt.% LiNO3, volume 20 μL.

[0051] The battery is assembled in a glove box under an argon atmosphere with oxygen <1ppm.

[0052] Example 1: Preparation of Mo2C MXene: 90 mL of hydrofluoric acid was added to a 150 mL polytetrafluoroethylene (PTFE) liner. 3 g of Mo2Ga2C MAX material was slowly added to the hydrofluoric acid solution. The liner was then sealed with a perforated cap, heated and stirred at 60°C for 5 days, centrifuged and washed with water until neutral, and vacuum dried for 24 hours to obtain Mo2C MXene powder. Figure 1 As shown, the XRD pattern of the obtained Mo2C MXene is significantly different from that of Mo2Ga2C MAX material. The characteristic peaks of Mo2Ga2C MAX material disappear noticeably between 30 and 50 degrees. Meanwhile, characteristic peaks of Mo2C MXene appear before 10 degrees, proving the successful synthesis of Mo2C MXene material. See also... Figure 2 a. You can see the layered structure.

[0053] Dissolve 300 mg ammonium molybdate, 124 mg glucose and 770 mg thiourea in a 100 mL polytetrafluoroethylene liner containing 40 mL deionized water and stir for 0.5 hours to form solution A.

[0054] Add 50 mg of Mo2C MXene to solution A and stir for 0.5 hours.

[0055] The polytetrafluoroethylene liner was transferred to a stainless steel reactor and placed in a forced-air drying oven at 200°C for 24 hours.

[0056] The reaction product was centrifuged and washed with water until neutral, and then freeze-dried for 2 days to obtain the precursor powder.

[0057] The precursor powder was calcined at 500°C for 2 hours in an argon atmosphere in a tube furnace to obtain the MoS2-Mo2C MXene composite material. (See also...) Figure 1 It exhibits obvious characteristic peaks of MoS2. For example... Figure 2 b. MoS2 nanosheets are uniformly grown on the surface of Mo2C MXene.

[0058] The obtained material was coated onto the surface of a commercial separator to a thickness of 40 micrometers, and the battery was assembled for electrochemical performance testing. Figure 3 As shown, the cyclic voltammograms of the assembled symmetrical cell reveal that the membrane modified with the MoS2-Mo2C MXene composite material exhibits a more pronounced redox peak and a stronger response current compared to Mo2C MXene, indicating that the membrane modified with the MoS2-Mo2C MXene composite material has a better catalytic reaction rate. Figure 4 As shown, the cycling performance was tested at a current density of 1 C. After 500 cycles, the MoS2-Mo2C MXene composite still exhibited a strength of 592 mAh g⁻¹. -1The high specific capacity indicates stable cycling performance. Similarly, rate performance was tested at different current densities, and the MoS2-Mo2C MXene composite maintained a high specific capacity at various current densities (see [reference]). Figure 5 Electrochemical tests show that the MoS2-Mo2C MXene composite material-modified separator can inhibit polysulfide shuttle and catalyze polysulfide conversion. Therefore, it improves the cycle and rate performance of lithium-sulfur batteries.

[0059] Example 2, Preparation of Mo2C MXene: This step is the same as the preparation of Mo2C MXene in Example 1;

[0060] Dissolve 300 mg ammonium molybdate, 248 mg glucose and 770 mg thiourea in a 100 mL polytetrafluoroethylene liner containing 40 mL deionized water and stir for 0.5 hours to form solution A.

[0061] Add 50 mg of Mo2C MXene to solution A and stir for 0.5 hours.

[0062] The polytetrafluoroethylene liner was transferred to a stainless steel reactor and placed in a forced-air drying oven at 200°C for 24 hours.

[0063] The reaction product was centrifuged and washed with water until neutral, and then freeze-dried for 2 days to obtain the precursor powder.

[0064] The precursor powder was calcined at 500°C for 2 hours in an argon atmosphere in a tube furnace to obtain the MoS2-Mo2C MXene composite material.

[0065] The obtained material was coated onto a commercial separator surface to a thickness of 40 micrometers, and the resulting battery was assembled for electrochemical performance testing. Cycling performance was tested at a 1 C current density; after 500 cycles, the MoS2-Mo2C MXene composite still exhibited a capacity of 575 mAh g / g. -1 The specific capacity indicates stable cycling performance.

[0066] Example 3: Preparation of Mo2C MXene: This step is the same as the preparation of Mo2C MXene in Example 1;

[0067] Dissolve 600 mg ammonium molybdate, 124 mg glucose and 1540 mg thiourea in a 100 mL polytetrafluoroethylene liner containing 40 mL deionized water and stir for 0.5 hours to form solution A.

[0068] Add 50 mg of Mo2C MXene to solution A and stir for 0.5 hours.

[0069] The polytetrafluoroethylene liner was transferred to a stainless steel reactor and placed in a forced-air drying oven at 200°C for 24 hours.

[0070] The reaction product was centrifuged and washed with water until neutral, and then freeze-dried for 2 days to obtain the precursor powder.

[0071] The precursor powder was calcined at 500°C for 2 hours in an argon atmosphere in a tube furnace to obtain the MoS2-Mo2C MXene composite material.

[0072] The obtained material was coated onto a commercial separator surface to a thickness of 40 micrometers, and the resulting battery was assembled for electrochemical performance testing. Cycling performance was tested at a 1 C current density; after 500 cycles, the MoS2-Mo2C MXene composite still exhibited a capacity of 553 mAh g / g. -1 The specific capacity indicates stable cycling performance.

[0073] Compared with Examples 2 and 3, Example 1 differs in the amount of raw materials used. Example 1 has the best performance because under the conditions of Example 1, MoS2 can be uniformly nucleated and grown on the surface of Mo2C MXene, and the growth amount is optimal, which is beneficial to improving battery performance.

[0074] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. The application of MoS2-Mo2C MXene composite material in the preparation of lithium-sulfur battery separators, characterized in that, The MoS2-Mo2C MXene composite material was prepared by the following method: Step S1: Preparation of Mo2C MXene: Mo2Ga2C MAX material is slowly added to hydrofluoric acid solution, heated and stirred in a polytetrafluoroethylene liner, and etched to obtain Mo2C MXene powder A; Step S2: Dissolve molybdate, glucose and sulfur source in water and stir to form a homogeneous solution A; Step S3: Add powder A to solution A and stir. After hydrothermal reaction, the precursor product is obtained. The hydrothermal temperature is 180-200℃ and the reaction time is 18-24 hours. Step S4: Wash the precursor product with water until neutral, and freeze-dry to obtain precursor powder B; Step S5: Calcine the obtained powder B in argon to obtain the MoS2-Mo2C MXene composite material; MoS2-Mo2C MXene composite material and conductive carbon were mixed and ground evenly. The binder was dissolved in an organic solvent. The evenly ground material was added to the organic solvent containing the binder to form a slurry, which was then applied to the surface of the separator. The mixture was then vacuum dried to obtain the MoS2-Mo2C MXene modified lithium-sulfur battery separator.

2. The application of the MoS2-Mo2C MXene composite material according to claim 1 in the preparation of lithium-sulfur battery separators, characterized in that, In step S1, the amount of Mo2Ga2C MAX material is 2-3 grams, the amount of hydrofluoric acid is 80-100 ml, the heating temperature is 55-60℃, and the etching time is 5-6 days.

3. The application of the MoS2-Mo2C MXene composite material according to claim 1 in the preparation of lithium-sulfur battery separators, characterized in that, In step S2, the molybdate is either ammonium molybdate or sodium molybdate, the sulfur source is either thiourea or thioacetamide, and the stirring time is 0.5-1 hour.

4. The application of the MoS2-Mo2C MXene composite material according to claim 3 in the preparation of lithium-sulfur battery separators, characterized in that, In step S2, the amount of ammonium molybdate is 300-600 mg, the amount of thiourea is 770-1540 mg, and the amount of glucose is 124-248 mg.

5. The application of the MoS2-Mo2C MXene composite material according to claim 1 in the preparation of lithium-sulfur battery separators, characterized in that, In step S3, powder A is 50-100 mg, and the stirring time is 0.5-1 hour.

6. The application of the MoS2-Mo2C MXene composite material according to claim 1 in the preparation of lithium-sulfur battery separators, characterized in that, In step S4, the freeze-drying time is 1-2 days.

7. The application of the MoS2-Mo2C MXene composite material according to claim 1 in the preparation of lithium-sulfur battery separators, characterized in that, In step S5, the calcination temperature is 400-600ºC and the calcination time is 1-2 hours.

8. The application of the MoS2-Mo2C MXene composite material according to claim 1 in the preparation of lithium-sulfur battery separators, characterized in that, The conductive carbon is one of Super P and acetylene black, and the binder is polyvinylidene fluoride; the weight percentage of the MoS2-Mo2CMXene composite material is 70-80%, the weight percentage of conductive carbon is 10-20%, and the weight percentage of binder is 10%; the drying temperature is 50-60℃, and the thickness of the membrane coating is 30-60 micrometers.

Images