A cobalt / molecular sieve catalyst and its preparation method and application
By loading a cobalt catalyst onto a molecular sieve, a modified lithium-sulfur battery separator was prepared, which solved the problem of polysulfide shuttle effect, achieved high-efficiency electrochemical performance and stable cycle life of the lithium-sulfur battery, and improved the electrochemical performance of the battery and the mechanical properties of the separator.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG WANLI UNIV
- Filing Date
- 2026-01-27
- Publication Date
- 2026-06-02
AI Technical Summary
The polysulfide shuttle effect is severe in existing lithium-sulfur batteries, leading to battery cycle degradation. Traditional polypropylene separators are difficult to effectively adsorb and convert polysulfides, thus affecting battery performance.
Cobalt catalysts were loaded onto molecular sieves and prepared by impregnation and high-temperature calcination. The pore structure of the molecular sieves confines the cobalt and provides active sites, thereby modifying lithium-sulfur battery membranes to adsorb and catalyze polysulfides.
It improves the electrochemical performance of lithium-sulfur batteries, suppresses the shuttle effect of polysulfides, and exhibits excellent rate performance and stable cycle life. The modified separator layer does not shed powder after bending and folding, and has excellent mechanical properties and adhesion stability.
Smart Images
Figure CN122136569A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst preparation and battery energy storage technology, and relates to a cobalt / molecular sieve catalyst, its preparation method and application. Background Technology
[0002] Global energy consumption continues to rise, particularly the widespread use of oil in transportation, which has negatively impacted the global economy and environment. With the increasing emphasis on sustainable development, clean, safe, and renewable energy sources (such as solar and wind power) have received widespread attention and are developing rapidly. However, these energy sources are limited by factors such as time, space, season, and climate, exhibiting intermittency and randomness, making them difficult to utilize effectively and leading to increased wind and solar power curtailment. Therefore, developing efficient energy storage technologies has become crucial. Among various energy storage technologies, electrical energy storage is the core technology for solving the problem of power imbalance, effectively addressing geographical and temporal limitations. Lithium-sulfur (Li-S) batteries are considered a promising electrochemical energy storage device, primarily because the natural resources required for their preparation are abundant, the sulfur component is low-cost, and they possess excellent theoretical energy density (approximately 2600 W·h·kg⁻¹). -1 ) and high specific capacity (1675 mAh·g) -1 However, the polysulfide "shuttle effect" in lithium-sulfur batteries leads to severe cycle degradation, which seriously limits their large-scale production and application.
[0003] To date, various strategies have been developed to address the aforementioned problems. For example, exploring host materials with high conductivity, polarity, and porosity to encapsulate sulfur cathodes can improve the affinity and conversion rate of polysulfides. However, these strategies cannot completely prevent the shuttle effect of soluble polysulfides from the sulfur cathode to the lithium anode through the membrane. The membrane in the electrolyte can isolate the cathode and anode to some extent, blocking the polysulfide shuttle effect. However, traditional polypropylene (PP) membranes are difficult to promote the adsorption and conversion of polysulfides. Therefore, it is necessary to explore ideal materials to modify commercial membranes to achieve efficient adsorption and kinetic conversion of polysulfides.
[0004] Due to their high specific surface area, porosity, and good chemical stability, molecular sieve materials can achieve strong physical adsorption and chemical catalysis of polysulfides. However, it is difficult to obtain excellent lithium-sulfur battery performance by simply modifying traditional polypropylene (PP) membranes with molecular sieve materials. To address this issue, it is necessary to rationally construct more active centers on molecular sieves to improve their catalytic performance. Molecular sieves are currently a commonly used catalyst support, and loading cobalt metal as a catalyst onto them is feasible. Their unique pore structure and confinement effect can effectively anchor cobalt species (such as elemental Co, Co nanoclusters, or CoO). xThis prevents the aggregation of active components. When this composite catalyst is applied to lithium-sulfur battery separators, the cobalt active sites can effectively adsorb polysulfides, promoting their rapid conversion.
[0005] Therefore, it is necessary to design a method for preparing a molecular sieve-supported single-atom catalyst and its application in lithium-sulfur battery separators to solve the above problems. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention proposes a molecular sieve-supported cobalt catalyst, its preparation method, and its application. The catalyst is prepared by impregnation using a method that supports metallic cobalt (such as elemental Co, Co nanoclusters, or CoO). x The catalyst is uniformly loaded in Silicalite-1 molecular sieve, thus providing a large number of active sites. This enables the catalyst to exhibit strong adsorption of polysulfides and superior catalytic activity. It can be used to modify the separator of lithium-sulfur batteries, accelerate the conversion of polysulfides, suppress the shuttle effect, and improve the electrochemical performance of lithium-sulfur batteries.
[0007] To achieve the above objectives, the present invention adopts the following technical solution;
[0008] A method for preparing a cobalt / molecular sieve catalyst includes the following steps:
[0009] S1: Dissolve the molecular sieve, then impregnate it in a cobalt-containing metal salt solution, sonicate, wash, and dry to obtain the precursor;
[0010] S2: After grinding the precursor obtained in step S1, calcine it at 300℃-600℃ for 2-5 hours in an inert gas atmosphere; then, add the calcined product and dopamine hydrochloride together to a citric acid buffer solution, sonicate, stir, wash, and dry.
[0011] S3: Grind the dried product from step S2, calcine it at 700℃-1000℃ for 2-5 hours in an inert gas atmosphere, and then calcine it in air at 300℃-500℃ for 3-5 hours to obtain the cobalt / molecular sieve catalyst.
[0012] Specifically, a certain amount of molecular sieve (e.g., Silicalite-1) powder is soaked in a solution containing Co metal salt and impregnated for a period of time under constant temperature conditions. Then, ultrasonic treatment is used to ensure that metal ions are uniformly dispersed and adsorbed on the channels and surface of the molecular sieve. Next, through a high-temperature reduction process, the pore structure of the molecular sieve is used to confine the cobalt metal to obtain a molecular sieve-supported cobalt metal catalyst.
[0013] Preferably, in step S1, the molecular sieve is pretreated by dispersing the molecular sieve powder in ethanol and adjusting the pH value to 8-10; the ratio of the amount of molecular sieve to ethanol is 0.06g~1g:30~60mL.
[0014] Preferably, the inert atmosphere includes nitrogen, argon, or helium.
[0015] Preferably, the ultrasonic treatment temperature in step S1 is 35-45℃, and the total immersion time is 20-48 hours.
[0016] Preferably, the molecular sieve is Silicalite-1 molecular sieve.
[0017] Preferably, the cobalt salt in step S1 is cobalt chloride, and the mass ratio of molecular sieve to cobalt chloride is 0.4 to 5:1.
[0018] Preferably, in step S2, the amount of dopamine hydrochloride added is 0.08-0.1 g / g relative to the mass of the molecular sieve; the amount of the citric acid buffer solution is 100-300 mL; and the mixture is stirred for 10-24 hours after ultrasonic treatment for 20-40 minutes.
[0019] This invention also claims protection for the cobalt / molecular sieve catalyst material obtained by the preparation method described above.
[0020] Furthermore, it protects the application of the cobalt / molecular sieve catalyst material in the modified separator of lithium-sulfur batteries.
[0021] This invention claims protection for a modified separator for lithium-sulfur batteries, comprising mixing the cobalt / molecular sieve catalyst material as a catalyst, conductive carbon black and polyvinylidene fluoride in a mass ratio of (6-9):(0.5-3):(0.5-1), adding N-methylpyrrolidone to form a uniform slurry, coating the slurry onto one side of a polypropylene separator, and drying it to obtain the final product.
[0022] The present invention also claims a lithium-sulfur battery, characterized in that it comprises a positive electrode, a negative electrode, an electrolyte, and a modified separator for the lithium-sulfur battery.
[0023] This invention prepares a cobalt metal catalyst supported on Silicalite-1 molecular sieve and applies it to the membrane layer of a modified lithium-sulfur battery. The lithium-sulfur battery exhibits excellent rate performance and stable cycle life. The membrane layer does not show powder shedding after bending and folding, demonstrating excellent mechanical properties and adhesion stability.
[0024] Compared with the prior art, the advantages of the present invention are:
[0025] This invention utilizes molecular sieves as a carrier, leveraging their high surface area and regular pore structure to effectively load metallic Co onto their surface and within the pores. This provides ample active sites for the conversion of polysulfides, enhancing the catalytic performance of the catalyst. When used as a modified coating for lithium-sulfur battery separators, it can effectively improve the electrochemical performance of lithium-sulfur batteries, demonstrating broad application prospects.
[0026] Molecular sieve-supported cobalt catalysts exhibit excellent rate performance and stable cycle life. Using this catalyst to modify membranes for lithium-sulfur battery assembly resulted in superior battery performance. After 100 cycles at 0.2C, the specific capacity remained as high as 1050 mAh·g. -1 The introduction of unique metal single-atom sites was found to suppress the shuttle effect by improving the adsorption and kinetic transformation of polysulfides, thereby enhancing the performance of Li-S batteries. Attached Figure Description
[0027] Figure 1 The XRD pattern is shown for the Silicalite-1 supported cobalt catalyst prepared in Example 1.
[0028] Figure 2 SEM image of the Silicalite-1 supported cobalt catalyst prepared in Example 1.
[0029] Figure 3 SEM image of the membrane modified with the Silicalite-1 supported cobalt catalyst prepared in Example 1.
[0030] Figure 4 The capacity retention rate of the Silicalite-1 supported cobalt catalyst prepared in Example 1 after 100 cycles at 0.2C. Detailed Implementation
[0031] The following specific embodiments of the present invention will provide a detailed and comprehensive description of the technical solutions of the present invention. It should be noted that the provided embodiments represent only a part of the present invention, and not all of it. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0032] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods; unless otherwise specified, the materials and reagents used are commercially available reagents and materials, and the commercially available raw materials are used to remove insoluble matter and other impurities by general filtration methods.
[0033] This invention provides a method for preparing a molecular sieve-supported cobalt catalyst. The method includes: immersing a molecular sieve in a solution containing a Co metal salt, impregnating it for a certain period of time under constant temperature conditions, and then treating it with ultrasound to ensure that metal ions are uniformly dispersed and adsorbed on the pores and surface of the molecular sieve; preparing a molecular sieve-supported cobalt catalyst, thereby obtaining cobalt through a pore confinement strategy and chemical anchoring.
[0034] The metal salt solution is obtained by dissolving an appropriate amount of cobalt chloride (CoCl2) in deionized water to prepare a metal salt solution of the desired concentration. The constant temperature condition is 35-45°C, and the immersion time is 20-48 hours.
[0035] The preparation of molecular sieve-supported cobalt catalysts specifically includes the following steps:
[0036] S1: Place the dried molecular sieve powder in 50-80 mL of anhydrous ethanol, stir until homogeneous, then add sodium hydroxide aqueous solution to adjust the pH to approximately 8-10. Next, add cobalt chloride (CoCl2) metal salt solution and perform magnetic stirring and ultrasonic treatment (20-40 minutes) to ensure uniform dispersion of the metal salt solution. Wash the sample with anhydrous ethanol and vacuum dry at 70℃-100℃ for 10-24 hours.
[0037] S2: After grinding the dried sample, place it in a porcelain boat and calcine it at 300℃-600℃ for 2-5 hours under an argon (Ar) atmosphere. Then, add dopamine hydrochloride to the calcined sample, dissolve it in 100ml-300ml of citric acid buffer solution, sonicate (20-40 minutes), and stir for 10-24 hours. Wash the sample with anhydrous ethanol and vacuum dry it at 70℃-100℃ for 10-24 hours.
[0038] S3: Grind the dried sample and then place it in a porcelain boat. Calcinate the sample at 700℃-1000℃ for 2-5 hours under an Ar atmosphere to obtain a brown sample. Spread the brown sample evenly in the porcelain boat and calcine it in air at 300℃-500℃ for 3-5 hours to obtain a white sample, which is the cobalt-supported molecular sieve catalyst.
[0039] The specific preparation method of the modified lithium-sulfur battery separator layer is as follows: First, a molecular sieve-supported cobalt catalyst, conductive carbon black, and polyvinylidene fluoride (PVDF) are mixed in a certain mass ratio and then coated onto one side of a commercial PP separator in N-methylpyrrolidone (NMP). The modified separator is then dried in a vacuum oven to obtain a molecular sieve-supported cobalt catalyst-modified separator.
[0040] The mass ratio of the molecular sieve-supported cobalt catalyst, conductive carbon black, and PVDF is 0.6-0.9:0.1-0.3:0.1-0.2.
[0041] Membrane-assembled lithium-sulfur batteries: The electrolyte consisted of 1 M LiTFSI and 1% LiNO3 in a 1:1 V / V solution of 1,3-dioxane (DOL) and dimethoxymethane (DME). Metallic lithium was used as the negative electrode. The coin cell (CR2032) was manufactured in a glove box under an Ar atmosphere. Electrochemical impedance spectroscopy was measured in the frequency range of 0.01–100 kHz on the same ivium electrochemical workstation. Charge-discharge tests were performed in the voltage range of 1.7–2.8 V on the Neware battery testing system.
[0042] Example 1
[0043] Silicalite-1 powder was dried in an oven at 100°C for 2 hours. 1 g of Silicalite-1 molecular sieve powder was dissolved in 60 ml of anhydrous ethanol, stirred thoroughly, and sodium hydroxide was added dropwise to adjust the pH to approximately 9. 0.2 g of cobalt chloride (CoCl2) was dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. This metal salt solution was added to the Silicalite-1 molecular sieve and impregnated at a constant temperature of 40°C for 24 hours (including 30 minutes of ultrasonic treatment). The sample was then washed with anhydrous ethanol and vacuum dried at 80°C for 12 hours.
[0044] The dried sample was ground and placed in a porcelain boat, then calcined at 350°C for 2 hours under an argon (Ar) atmosphere. After calcination, 0.1 g of dopamine hydrochloride was added to the sample, dissolved in 300 mL of citric acid buffer solution, and sonicated (for 30 minutes), followed by stirring for 12 hours. The sample was washed with anhydrous ethanol and then vacuum dried at 70°C for 12 hours.
[0045] The dried sample was ground and then placed in a ceramic boat. It was calcined at 800°C for 3 hours under an Ar atmosphere to obtain a brown sample. The brown sample was then spread evenly in the ceramic boat and calcined in air at 400°C for 3 hours to obtain a white sample, which is the catalyst Co / Silicalite-1.
[0046] A cobalt catalyst supported on Silicalite-1 molecular sieve, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP) to obtain a uniform paste slurry, which was then coated onto one side of a commercial PP membrane. The modified membrane was dried in a vacuum oven to obtain a membrane modified with the cobalt catalyst supported on Silicalite-1 molecular sieve.
[0047] A lithium-sulfur battery using a membrane modified with a cobalt catalyst supported on Silicalite-1 molecular sieve can achieve a power output of 1380 mAh g at 0.2C. -1High reversible specific capacity, with a specific capacity of 1050 mAhg after 100 cycles. -1 .
[0048] Example 2
[0049] Silicalite-1 powder was dried in an oven at 100°C for 5 hours. 0.8 g of Silicalite-1 molecular sieve powder was dissolved in 50 ml of anhydrous ethanol, stirred thoroughly, and sodium hydroxide was added dropwise to adjust the pH to approximately 9. 0.2 g of cobalt chloride (CoCl2) was dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. This metal salt solution was added to the Silicalite-1 molecular sieve and impregnated at a constant temperature of 30°C for 48 hours (including 30 minutes of ultrasonic treatment). The sample was then washed with anhydrous ethanol and vacuum dried at 80°C for 12 hours.
[0050] After drying, the sample was ground and placed in a porcelain boat, then calcined at 350°C for 2 hours under an argon (Ar) atmosphere. 0.08 g of dopamine hydrochloride was added to the calcined sample, dissolved in 200 mL of citric acid buffer solution, and sonicated (for 30 minutes), followed by stirring for 12 hours. The sample was washed with anhydrous ethanol and then vacuum dried at 70°C for 12 hours.
[0051] The dried sample was ground and then placed in a ceramic boat. It was calcined at 800°C for 3 hours under an Ar atmosphere to obtain a brown sample. The brown sample was then spread evenly in the ceramic boat and calcined in air at 400°C for 3 hours to obtain a white sample, which is the catalyst Co / Silicalite-1.
[0052] A cobalt catalyst supported on Silicalite-1 molecular sieve, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 7:2:1 and dissolved in N-methylpyrrolidone (NMP) to obtain a uniform paste slurry, which was then coated onto one side of a commercial PP membrane. The modified membrane was dried in a vacuum oven to obtain a membrane modified with the cobalt catalyst supported on Silicalite-1 molecular sieve.
[0053] A lithium-sulfur battery using a membrane modified with a cobalt catalyst supported on Silicalite-1 molecular sieve can achieve a 1225 mAh / g e capacity at 0.2C. -1 High reversible specific capacity, with a specific capacity of 917 mAhg after 100 cycles. -1 .
[0054] Example 3
[0055] Silicalite-1 powder was dried in an oven at 100°C for 6 hours. 0.07 g of Silicalite-1 molecular sieve powder was dissolved in 30 ml of anhydrous ethanol, stirred thoroughly, and sodium hydroxide was added dropwise to adjust the pH to approximately 9. 0.18 g of cobalt chloride (CoCl2) was dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. This metal salt solution was added to the Silicalite-1 molecular sieve and impregnated at a constant temperature of 25°C for 48 hours (including 30 minutes of ultrasonic treatment). The sample was then washed with anhydrous ethanol and vacuum dried at 80°C for 12 hours.
[0056] The dried sample was ground and placed in a porcelain boat, then calcined at 350°C for 2 hours under an argon (Ar) atmosphere. After calcination, 0.08 g of dopamine hydrochloride was added to the sample, dissolved in 100 mL of citric acid buffer solution, and sonicated (for 30 minutes), followed by stirring for 12 hours. The sample was washed with anhydrous ethanol and then vacuum dried at 70°C for 12 hours.
[0057] The dried sample was ground and then placed in a ceramic boat. It was calcined at 800°C for 3 hours under an Ar atmosphere to obtain a brown sample. The brown sample was then spread evenly in the ceramic boat and calcined in air at 400°C for 3 hours to obtain a white sample, which is the catalyst Co / Silicalite-1.
[0058] A cobalt catalyst supported on Silicalite-1 molecular sieve, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 6:3:1 and dissolved in N-methylpyrrolidone (NMP) to obtain a uniform paste slurry, which was then coated onto one side of a commercial PP membrane. The modified membrane was dried in a vacuum oven to obtain a membrane modified with the cobalt catalyst supported on Silicalite-1 molecular sieve.
[0059] A lithium-sulfur battery using a membrane modified with a cobalt catalyst supported on Silicalite-1 molecular sieve can achieve a power output of 1025 mAh g⁻¹ at 0.2C. -1 High reversible specific capacity, with a specific capacity of 785 mAhg after 100 cycles. -1 .
[0060] Example 4
[0061] Silicalite-1 powder was dried in an oven at 100°C for 2 hours. 0.06 g of Silicalite-1 molecular sieve powder was dissolved in 50 ml of anhydrous ethanol, stirred thoroughly, and sodium hydroxide was added dropwise to adjust the pH to approximately 9. 0.15 g of cobalt chloride (CoCl2) was dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. This metal salt solution was added to the Silicalite-1 molecular sieve and impregnated at a constant temperature of 40°C for 48 hours (including 30 minutes of ultrasonic treatment). The sample was then washed with anhydrous ethanol and vacuum dried at 80°C for 12 hours.
[0062] After drying, the sample was ground and placed in a porcelain boat, then calcined at 350°C for 2 hours under an argon (Ar) atmosphere. 0.08 g of dopamine hydrochloride was added to the calcined sample, dissolved in 200 mL of citric acid buffer solution, and sonicated (for 30 minutes), followed by stirring for 12 hours. The sample was washed with anhydrous ethanol and then vacuum dried at 70°C for 12 hours.
[0063] The dried sample was ground and then placed in a ceramic boat. It was calcined at 800°C for 3 hours under an Ar atmosphere to obtain a brown sample. The brown sample was then spread evenly in the ceramic boat and calcined in air at 400°C for 3 hours to obtain a white sample, which is the catalyst Co / Silicalite-1.
[0064] A cobalt catalyst supported on Silicalite-1 molecular sieve, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 9:0.5:0.5 and dissolved in N-methylpyrrolidone (NMP) to obtain a uniform paste slurry, which was then coated onto one side of a commercial PP membrane. The modified membrane was dried in a vacuum oven to obtain a membrane modified with the cobalt catalyst supported on Silicalite-1 molecular sieve.
[0065] A lithium-sulfur battery using a membrane modified with a cobalt catalyst supported on Silicalite-1 molecular sieve can achieve a power output of 975 mAh g⁻¹ at 0.2C. -1 High reversible specific capacity, with a specific capacity of 750 mAhg after 100 cycles. -1 .
[0066] Comparative Example 1
[0067] Silicate-2 powder was dried in an oven at 100°C for 2 hours. 1 g of Silicalite-2 molecular sieve powder was dissolved in 60 ml of anhydrous ethanol, stirred thoroughly, and sodium hydroxide was added dropwise to adjust the pH to approximately 9. 0.2 g of cobalt chloride (CoCl2) was dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. This metal salt solution was added to the Silicate-2 molecular sieve and impregnated at a constant temperature of 40°C for 24 hours (including 30 minutes of ultrasonic treatment). The sample was then washed with anhydrous ethanol and vacuum dried at 80°C for 12 hours.
[0068] The dried sample was ground and placed in a porcelain boat, then calcined at 350°C for 2 hours under an argon (Ar) atmosphere. After calcination, 0.1 g of dopamine hydrochloride was added to the sample, dissolved in 300 mL of citric acid buffer solution, and sonicated (for 30 minutes), followed by stirring for 12 hours. The sample was washed with anhydrous ethanol and then vacuum dried at 70°C for 12 hours.
[0069] The dried sample was ground and then placed in a porcelain boat. It was calcined at 800°C for 3 hours under an Ar atmosphere to obtain a brown sample. The brown sample was then spread evenly in the porcelain boat and calcined in air at 400°C for 3 hours to obtain a white sample, which is the catalyst Co-Silicate-2.
[0070] Silicate-2 supported cobalt catalyst, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP) to obtain a uniform paste slurry, which was then coated onto one side of a commercial PP membrane. The modified membrane was dried in a vacuum oven to obtain the Silicate-2 supported cobalt catalyst modified membrane.
[0071] A lithium-sulfur battery using a membrane modified with a Silicate-2 supported cobalt catalyst can achieve a capacity of 985 mAh / g at 0.2C. -1 High reversible specific capacity, with a specific capacity of 650 mAhg after 100 cycles. -1 .
[0072] Compared with Examples 1, 2, 3, and 4, the difference is that all the carrier molecular sieves are Silicate-2 molecular sieves with a similar pore structure to Silicalite-1, while the other steps are roughly the same as in Example 1.
[0073] Comparative Example 2
[0074] Silicalite-1 powder was dried in an oven at 100°C for 5 hours. 0.8 g of Silicalite-1 molecular sieve powder was dissolved in 50 ml of anhydrous ethanol, stirred thoroughly, and sodium hydroxide was added dropwise to adjust the pH to approximately 9. 0.2 g of cobalt chloride (CoCl2) was dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. This metal salt solution was added to the Silicalite-1 molecular sieve and impregnated at a constant temperature of 30°C for 48 hours (including 30 minutes of ultrasonic treatment). The sample was then washed with anhydrous ethanol and vacuum dried at 80°C for 12 hours.
[0075] After drying, the sample was ground and placed in a porcelain boat, then calcined at 350°C for 2 hours under an argon (Ar) atmosphere. 0.08 g of dopamine hydrochloride was added to the calcined sample, dissolved in 200 mL of citric acid buffer solution, and sonicated (for 30 minutes), followed by stirring for 12 hours. The sample was washed with anhydrous ethanol and then vacuum dried at 70°C for 12 hours.
[0076] The dried sample was ground and then placed in a ceramic boat and calcined at 800°C for 3 hours under an Ar atmosphere to obtain a brown sample. The yellow sample was spread evenly in the ceramic boat and calcined in air at 400°C for 3 hours to obtain a white sample, which is the catalyst Co-Silicalite-1.
[0077] A cobalt catalyst supported on Silicalite-1 molecular sieve and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 9:1 and dissolved in N-methylpyrrolidone (NMP) to obtain a uniform paste slurry, which was then coated onto one side of a commercial PP membrane. The modified membrane was dried in a vacuum oven to obtain a membrane modified with the cobalt catalyst supported on Silicalite-1 molecular sieve.
[0078] A lithium-sulfur battery using a membrane modified with a cobalt catalyst supported on Silicalite-1 molecular sieve can achieve a power output of 975 mAh g⁻¹ at 0.2C. -1 High reversible specific capacity, with a specific capacity of 638 mAhg after 100 cycles. -1 .
[0079] Compared with Examples 1, 2, 3, and 4, the difference is that conductive carbon black was not added, while the other steps are roughly the same as in Example 1.
[0080] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the Co / S-1 (Silicalite-1) zeolite sample. No obvious diffraction peaks corresponding to metallic cobalt species were detected in Co / S-1, indicating that the cobalt species are highly dispersed in S-1.
[0081] Figure 2The images show scanning electron microscopy (SEM) images of the Co / S-1 zeolite sample. The images indicate that the original crystal morphology and size characteristics of Co / S-1 were preserved after cobalt loading, suggesting that the loading process did not cause significant structural changes to the zeolite framework.
[0082] Figure 3 Cross-sectional scanning electron microscope (SEM) images of Co / S-1 zeolite samples and CNT-coated PP separators. The images show that by coating the PP separator surface with a functional composite layer (Co / S-1@CNT) consisting of Co / S-1 and CNTs (carbon nanotubes), a dense layer of approximately 20 μm thickness was formed. This structural design not only effectively inhibits the free diffusion of LiPSs but also significantly reduces the charge transfer resistance.
[0083] Figure 4 The cycle performance test and charge-discharge curves of the Co / S-1 battery are shown. The curves indicate that the Co / S-1 battery has an initial discharge capacity of up to 1380 mAh g⁻¹ at a 0.2 C rate. -1 It still maintains approximately 1050 mAh g after 100 cycles. -1 .
[0084] This invention provides a method for preparing a molecular sieve-supported cobalt catalyst and its application in lithium-sulfur battery separators. An improved preparation method is used to load cobalt metal onto a molecular sieve, stabilizing the cobalt metal through a pore confinement strategy and chemical anchoring. The separator modified with the molecular sieve-supported cobalt catalyst exhibits excellent rate performance and stable cycle life in lithium-sulfur batteries.
[0085] Obviously, the above embodiments of the present invention are merely examples to clearly illustrate the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.
Claims
1. A method for preparing a cobalt / molecular sieve catalyst, characterized in that, Includes the following steps: S1: Dissolve the molecular sieve, then impregnate it in a cobalt-containing metal salt solution, sonicate, wash, and dry to obtain the precursor; S2: After grinding the precursor obtained in step S1, calcine it at 300℃-600℃ for 2-5 hours in an inert gas atmosphere. Subsequently, the calcined product and dopamine hydrochloride were added together to a citric acid buffer solution, sonicated, stirred, washed, and dried. S3: Grind the dried product from step S2, calcine it at 700℃-1000℃ for 2-5 hours in an inert gas atmosphere, and then calcine it in air at 300℃-500℃ for 3-5 hours to obtain the cobalt / molecular sieve catalyst.
2. The preparation method according to claim 1, characterized in that, In step S1, the molecular sieve is pretreated by dispersing the molecular sieve powder in ethanol and adjusting the pH value to 8-10. The ratio of molecular sieve to ethanol is 0.06g~1g:30~60mL.
3. The preparation method according to claim 1, characterized in that, In step S1, the ultrasonic treatment temperature is 35-45℃, and the total immersion time is 20-48 hours.
4. The preparation method according to claim 1, characterized in that, The molecular sieve is Silicalite-1 molecular sieve.
5. The preparation method according to claim 1, characterized in that, The cobalt salt mentioned in step S1 is cobalt chloride, and the mass ratio of molecular sieve to cobalt chloride is 0.4 to 5:
1.
6. The preparation method according to claim 1, characterized in that, In step S2, the amount of dopamine hydrochloride added is 0.08-0.1 g / g relative to the mass of the molecular sieve; the amount of citric acid buffer solution used is 100-300 mL; after ultrasonic treatment for 20-40 minutes, the mixture is stirred for 10-24 hours.
7. A cobalt / molecular sieve catalyst material obtained by the preparation method of claim 1.
8. The application of the cobalt / molecular sieve catalyst material according to claim 7 in the modified separator of lithium-sulfur battery.
9. A modified separator for lithium-sulfur batteries, characterized in that, The method involves mixing the cobalt / molecular sieve catalyst material as described in claim 7, conductive carbon black, and polyvinylidene fluoride in a mass ratio of (6-9):(0.5-3):(0.5-1), adding N-methylpyrrolidone to form a uniform slurry, coating the slurry onto one side of a polypropylene diaphragm, and drying it to obtain the final product.
10. A lithium-sulfur battery, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the separator is the modified separator for lithium-sulfur batteries as described in claim 9.