A Co 0.5 Ni 0.5 Preparation method of Te2 nanoparticle / three-dimensional carbon sheet composite material and its application in lithium-sulfur batteries

Abstract

The present invention belongs to the field of inorganic functional material synthesis, and particularly relates to a Co 0.5 Ni 0.5 Preparation method of Te2 nanoparticle / three-dimensional carbon sheet composite material and its application in lithium-sulfur battery. This is achieved by the following steps: (1) one-step high-temperature calcination method to prepare three-dimensional carbon sheet as a conductive skeleton; (2) ZIF-67 nanoparticles are loaded on the surface of the carbon sheet; (3) Ni is introduced under heating reflux conditions. 2+ , etching to obtain CoNi‑LDH / three-dimensional carbon sheet composite precursor; (4) high temperature tellurization treatment to prepare Co 0.5 Ni 0.5 Te2 nanoparticles / three-dimensional carbon sheet composites. Co 0.5 Ni 0.5 Te2 nanoparticles are evenly distributed on the carbon sheet surface, chemically adsorbing and catalyzing the kinetic conversion of polysulfide ions. Simultaneously, the three-dimensional carbon sheet, with its cross-linked network structure, provides continuous electron transport channels, ensuring rapid charge transfer. The synthesis method provided in this application is simple, universal, and highly reproducible; its application in lithium-sulfur battery separator coating materials can effectively improve battery specific capacity and cycling stability.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic functional material synthesis, and relates to a method for preparing a lithium-sulfur battery diaphragm functional coating material, specifically a Co 0.5 Ni 0.5 Preparation method of Te2 nanoparticle / three-dimensional carbon sheet composite material and its application in lithium-sulfur batteries. Background Art

[0002] Lithium-sulfur batteries have a high theoretical specific capacity (1672 mAh g -1 ) and energy density (~2600Wh kg -1 ), which is more than 5 times that of traditional lithium-ion batteries; and sulfur powder has the advantages of low price, abundant reserves, and non-toxicity. Therefore, it is considered to be one of the new generation of energy storage systems with development potential. However, the practical application of lithium-sulfur batteries still faces many challenges: for example, the insulating properties of sulfur and its discharge products hinder the transmission of electrons, resulting in hysteresis in the conversion kinetics of polysulfide ions and low actual specific capacity of the battery. Secondly, long-chain lithium polysulfides dissolve in the electrolyte and pass through the separator, diffuse and shuttle between the positive and negative electrodes, corrode the lithium sheet, and damage the battery cycle stability and coulombic efficiency. In addition, due to the sulfur (2.03g cm -3 ) and lithium sulfide (1.66 g cm -3 ) has a large density difference, and the volume of the electrode changes greatly before and after charging and discharging (~80%), which can easily lead to the collapse of the electrode structure.

[0003] Currently, researchers have conducted extensive modification work on traditional polypropylene separators, focusing on separator interface engineering design. Experiments have demonstrated that coating the separator surface with functional materials is an effective strategy for improving the performance of lithium-sulfur batteries. Carbon materials, characterized by their light weight, high conductivity, and rich pore structures, have primarily been used as functional separator coating materials in early research, primarily using carbon materials with various micromorphologies, such as graphene and carbon nanotubes / fibers. However, due to their non-polar surface properties, the bonding between them and polar polysulfides is weak, making it difficult to completely inhibit polysulfide shuttling through physical confinement alone. In contrast, transition metal compounds, due to their strong surface polarity, can chemically adsorb polysulfide ions to a large extent. Furthermore, some conductive metal compounds can catalyze the redox transformation of polysulfide ions. However, the inherent conductivity of most metal compounds is not ideal, which undoubtedly inhibits electron transport at the reaction interface, thereby reducing the electrocatalytic effect. Therefore, a superior separator coating material must meet the requirements of integrating conductivity, adsorption, and catalysis.

[0004] Transition metal compound / carbon composite materials have the advantages of both conductive carbon materials and polar metal compounds. As a diaphragm coating material, they can not only serve as an effective barrier to inhibit the shuttle of polysulfide, but also perform secondary adsorption and catalysis on the polysulfide ions escaping from the positive electrode, thereby improving the battery specific capacity and cycle stability. However, there is still some room for exploration to be explored, such as developing new polar compounds with metallic or semi-metallic properties, optimizing the electron transfer dynamics, and thus improving the catalytic efficiency. Compared with metal oxides, sulfides and selenides, transition metal tellurides have more metallic properties and high conductivity (such as NiS2 is 0.55 S m -1 , NiSe2 is 10 S m -1 , while NiTe2 is as high as 1.15 × 10 6 S m -1 ), which is beneficial to promoting the catalytic conversion of polysulfide ions. Therefore, exploring new transition metal telluride / carbon composite materials for separator functional coatings is of great research significance for optimizing the performance of lithium-sulfur batteries. Summary of the Invention

[0005] The object of the present invention is to provide a Co 0.5 Ni 0.5 The preparation method of Te2 nanoparticles / three-dimensional carbon sheet composite material is simple, universal and reproducible; and the Co 0.5 Ni 0.5 After Te2 nanoparticle / three-dimensional carbon sheet composite materials are used as lithium-sulfur battery separator coating materials, the battery has high specific capacity and good cycle stability.

[0006] Another object of the present invention is to provide the above-mentioned Co 0.5 Ni 0.5 Application of Te2 nanoparticles / three-dimensional carbon sheet composites in lithium-sulfur batteries.

[0007] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are as follows:

[0008] The present invention provides a Co 0.5 Ni 0.5 The preparation method of the Te2 nanoparticle / three-dimensional carbon sheet composite material comprises the following steps:

[0009] (1) Preparation of three-dimensional carbon sheets

[0010] Sodium citrate is calcined at high temperature in an inert atmosphere, and after being fully washed and dried, a three-dimensional carbon sheet skeleton is obtained;

[0011] (2) Preparation of ZIF-67 nanoparticles / three-dimensional carbon sheets

[0012] The three-dimensional carbon sheet skeleton was weighed and poured into a methanol solution containing cobalt nitrate. The mixture was stirred at room temperature and a methanol solution of 2-methylimidazole was added dropwise. The mixture was stirred evenly and allowed to stand. The mixture was washed and dried to obtain a ZIF-67 nanoparticle / three-dimensional carbon sheet composite.

[0013] (3) Preparation of CoNi-LDH / 3D carbon sheet precursor

[0014] The ZIF-67 / three-dimensional carbon sheet composite was weighed and placed in an ethanol solution of nickel nitrate, heated under reflux, stirred for several minutes, washed and dried to obtain a cobalt nickel double hydroxide CoNi-LDH / three-dimensional carbon sheet precursor;

[0015] (4) Co 0.5 Ni 0.5 Preparation of Te2 Nanoparticles / Three-Dimensional Carbon Sheet Composites

[0016] Weigh the CoNi-LDH / three-dimensional carbon sheet precursor and tellurium powder, stir and mix them evenly, and calcine them to obtain Co 0.5 Ni 0.5 Te2 nanoparticle / three-dimensional carbon sheet composite material.

[0017] Preferably, in step (1), the high-temperature calcination is sintering at a temperature of 700-900°C for 1-3 hours; and the inert atmosphere is Ar gas.

[0018] Preferably, in step (2), the ratio of the three-dimensional carbon sheet skeleton to the cobalt nitrate solution is 0.10-0.20 g:80 mL.

[0019] Preferably, in step (2), the concentration of the methanol solution of cobalt nitrate is 0.03 mol / L~0.06 mol / L; the concentration of the methanol solution of 2-methylimidazole is 0.12 mol / L~0.24 mol / L; and the volume ratio of the methanol solution containing cobalt nitrate to the methanol solution of 2-methylimidazole is 1:1.

[0020] Preferably, in step (2), the stirring time is 3 to 12 hours; and the standing time is 12 to 24 hours.

[0021] Preferably, in step (3), the concentration of the nickel nitrate-containing ethanol solution is 0.015 mol / L~0.02 mol / L; and the ratio of the ZIF-67 / three-dimensional carbon sheet composite to the nickel nitrate solution is 0.1~0.2 g:30-35 mL.

[0022] Preferably, in step (3), the heating reflux temperature is 70-90°C, and the heating reflux stirring time is 4-8 minutes.

[0023] Preferably, in step (4), the mass ratio of the CoNi-LDH / three-dimensional carbon sheet precursor to tellurium powder is 1:1.2-1.5.

[0024] Preferably, in step (4), the calcination is carried out by heating the temperature to 600-800°C at a heating rate of 2°C per minute and maintaining the temperature for 3-5 hours.

[0025] The present invention also provides a Co prepared by the above preparation method. 0.5 Ni 0.5 Application of Te2 nanoparticle / three-dimensional carbon sheet composites as functional coating materials for lithium-sulfur battery separators.

[0026] The Co synthesized by the present invention 0.5 Ni 0.5 Te2 nanoparticles / three-dimensional carbon sheet composite material integrates the multifunctionality of conductivity, adsorption and catalysis. The overall skeleton presents a cross-linked network structure, which is conducive to the continuous and rapid transmission of charge. The surface of the carbon sheet is based on CoNi-LDH derived Co 0.5 Ni 0.5 Te2 nanoparticles are essentially hexagonal in shape and relatively uniform in nanometer size. When coated on one side of the separator as a functional material, they effectively adsorb and promote the conversion kinetics of polysulfide ions, resulting in batteries demonstrating excellent specific capacity and cycle stability.

[0027] The beneficial effects of the present invention are:

[0028] 1) Co provided by the present invention 0.5 Ni 0.5 Te2 nanoparticle / three-dimensional carbon sheet composite materials have the characteristics of simple and universal synthesis method, easy availability of raw materials, and high reproducibility.

[0029] 2) CoNi-LDH-derived Co 0.5 Ni 0.5 Te2 nanoparticles are uniform in size and evenly distributed on the surface of the three-dimensional carbon sheet, effectively avoiding the phenomenon of particle agglomeration during high-temperature calcination; they can provide a large number of catalytic active sites, adsorb and accelerate the redox conversion of polysulfide ions.

[0030] 3) After it was applied as a separator coating material to lithium-sulfur batteries, the batteries showed high specific capacity and good cycle performance. -1 ) current density, the discharge capacity can still be maintained at 976.3 mAh g after 200 charge and discharge cycles. -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Co was prepared in Example 1 of the present invention 0.5 Ni0.5 Transmission electron microscopy or scanning electron microscopy (TEM and SEM images) of Te2 nanoparticle / 3D carbon sheet composites.

[0032] Figure 2 Co was prepared in Example 1 of the present invention 0.5 Ni 0.5 X-ray diffraction pattern (XRD pattern) of Te2 nanoparticles / 3D carbon sheets.

[0033] Figure 3 Co was prepared in Example 2 of the present invention 0.5 Ni 0.5 Transmission electron micrograph (TEM image) of Te2 nanoparticle / three-dimensional carbon sheet composite material.

[0034] Figure 4 Co prepared in Example 1 of the present invention 0.5 Ni 0.5 After Te2 nanoparticles / 3D carbon sheets are used as functional coating materials for lithium-sulfur battery separators, the cycling performance diagram of the relevant batteries under 0.5C conditions; among them, the left vertical axis is the specific capacity (Specific capacity), the right vertical axis is the Coulombic efficiency (Coulombic efficiency), and the horizontal axis is the cycle number (Cycle number). DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0036] Example 1

[0037] (1) Preparation of three-dimensional carbon sheets

[0038] Weigh 20 g of sodium citrate and pour it into a dry porcelain boat, place it in a tube furnace, and raise the temperature to 800°C at a rate of 5°C / min in an Ar atmosphere and maintain it for 1 hour. After it cools down, the calcined product is thoroughly washed and dried to obtain a three-dimensional carbon sheet skeleton.

[0039] (2) Preparation of ZIF-67 nanoparticles / three-dimensional carbon sheets

[0040] Weigh 0.15 g of the three-dimensional carbon sheet obtained in step (1), pour it into 80 mL of a methanol solution containing 0.03 mol / L cobalt nitrate, place it under a magnetic stirrer and stir at room temperature for 12 h, then add 80 mL of a methanol solution containing 0.12 mol / L 2-methylimidazole dropwise, stir for 3 h and let it stand for 24 h, filter the solution, wash and dry it to obtain a ZIF-67 nanoparticle / three-dimensional carbon sheet composite;

[0041] (3) Preparation of CoNi-LDH / 3D carbon sheet precursor

[0042] Weigh 0.16 g of the ZIF-67 / three-dimensional carbon sheet obtained in step (2) and place it in 35 mL of an ethanol solution containing 0.015 mol / L nickel nitrate. Heat and reflux it in an 80°C oil bath for 4 min. Filter the product, wash it, and dry it to obtain a cobalt nickel double hydroxide (CoNi-LDH) / three-dimensional carbon sheet precursor.

[0043] (4) Co 0.5 Ni 0.5 Preparation of Te2 Nanoparticles / Three-Dimensional Carbon Sheet Composites

[0044] Weigh 0.10 g of the CoNi-LDH / three-dimensional carbon sheet obtained in step (3) and 0.15 g of tellurium powder, stir and mix them evenly, place them in a tube furnace, introduce high-purity argon gas, and calcine at 600 ° C for 3 h with a heating rate of 2 ° C / min. After cooling to room temperature, the target material Co 0.5 Ni 0.5 Te2 nanoparticles / 3D carbon sheet composites.

[0045] Example 2

[0046] (1) Preparation of three-dimensional carbon sheets

[0047] Weigh 30 g of sodium citrate and pour it into a dry porcelain boat, place it in a tube furnace, and raise the temperature to 800°C at a rate of 5°C / min in an Ar atmosphere and maintain it for 1 hour. After it cools down, the calcined product is thoroughly washed and dried to obtain a three-dimensional carbon sheet skeleton.

[0048] (2) Preparation of ZIF-67 nanoparticles / three-dimensional carbon sheets

[0049] Weigh 0.10 g of the three-dimensional carbon sheet obtained in step (1), pour it into 80 mL of a methanol solution containing 0.06 mol / L cobalt nitrate, place it under a magnetic stirrer and stir it at room temperature for 12 h, then add 80 mL of a methanol solution containing 0.24 mol / L 2-methylimidazole dropwise, stir for 3 h and let it stand for 24 h, filter the solution, wash and dry it to obtain a ZIF-67 nanoparticle / three-dimensional carbon sheet composite;

[0050] (3) Preparation of CoNi-LDH / 3D carbon sheet precursor

[0051] Weigh 0.10 g of the ZIF-67 / three-dimensional carbon sheet obtained in step (2) and place it in 30 mL of an ethanol solution containing 0.017 mol / L nickel nitrate. Heat and reflux it in an 80°C oil bath for 4 min. Filter the product, wash it, and dry it to obtain a cobalt nickel double hydroxide (CoNi-LDH) / three-dimensional carbon sheet precursor.

[0052] (4) Co 0.5 Ni 0.5 Preparation of Te2 Nanoparticles / Three-Dimensional Carbon Sheet Composites

[0053] Weigh 0.10 g of the CoNi-LDH / three-dimensional carbon sheet obtained in step (3) and 0.15 g of tellurium powder, stir and mix them evenly, place them in a tube furnace, introduce high-purity argon gas, and calcine at 600 ° C for 3 h with a heating rate of 2 ° C / min. After cooling to room temperature, the target material Co 0.5 Ni 0.5 Te2 nanoparticles / 3D carbon sheet composites.

[0054] Effect Example 1

[0055] Figure 1 Co was prepared in Example 1 of the present invention 0.5 Ni 0.5 TEM or SEM images of Te2 nanoparticles / three-dimensional carbon sheet composites. It can be seen from the figure that after high-temperature tellurization treatment, Co2-based CoNi-LDH-derived Co 0.5 Ni 0.5 Te2 nanoparticles are evenly distributed on the surface of carbon sheets with a three-dimensional cross-linked structure. Their size is relatively uniform, with a particle size of less than 50nm, and there is no obvious particle agglomeration. Figure 2 For Co 0.5 Ni 0.5 X-ray diffraction pattern (XRD pattern) of Te2 nanoparticles / three-dimensional carbon sheet composite material, which proves that the phase of nanoparticles loaded on the surface of carbon sheet is Co 0.5 Ni 0.5 Te2 (PDF#97-062-4510).

[0056] Effect Example 2

[0057] Figure 3 Co was prepared in Example 2 of the present invention 0.5 Ni 0.5 TEM image of Te2 nanoparticles / 3D carbon sheet composite material. It can be seen that when the carbon sheet content is reduced and the concentration of cobalt nitrate and 2-methylimidazole is doubled, the Ni 2+ After etching and high-temperature tellurization treatment, NiCo-LDH-derived Co 0.5 Ni0.5 The content of Te2 nanoparticles has increased significantly and is more densely distributed on the surface of the three-dimensional carbon sheet.

[0058] Effect Example 3

[0059] The Co prepared in Example 1 0.5 Ni 0.5 The electrochemical performance of Te2 nanoparticle / 3D carbon sheet composite materials used as functional coating materials for lithium-sulfur battery separators was tested. The specific steps are as follows:

[0060] (1) Preparation of functional diaphragm:

[0061] Co prepared in Example 1 0.5 Ni 0.5 A Te2 nanoparticle / 3D carbon sheet composite, a conductive agent, and a binder were weighed in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added dropwise to form a slurry. Acetylene black was used as the conductive agent, and polyvinylidene fluoride (PVDF) was used as the binder. Using a film applicator, the slurry was evenly coated onto one side of a polypropylene separator (Celgard 2500) at a controlled thickness. The film was then placed in a 50°C oven for 8 hours. After drying, it was cut into 19 mm diameter discs.

[0062] (2) Battery assembly and testing:

[0063] The battery was assembled in a glove box, high-purity argon was used as the filling gas, lithium sheet was used as the negative electrode, and the positive electrode was a carbon / sulfur composite with a sulfur loading of 70 wt%. 0.5 Ni 0.5 A functional separator coated with Te2 nanoparticles / three-dimensional carbon sheets and a conventional unmodified polypropylene separator served as controls. An ethereal electrolyte containing 1 mol / L LiTFSI (lithium salt) and 2 wt% LiNO3 was added dropwise to wet the electrodes and separator. After battery assembly, the cells were left standing for 6 hours before electrochemical performance testing using a Blue Electric test system. The voltage window was 1.7-2.8 V.

[0064] (3) Result analysis:

[0065] Figure 4 It is the cycle performance diagram of the relevant battery. It can be seen from the figure that the use of Co 0.5 Ni 0.5 The battery with Te2 nanoparticles / 3D carbon sheet modified functional separator showed high specific capacity and good cycling performance. -1 ) current density, the discharge capacity can still be maintained at 976.3 mAh g after 200 charge and discharge cycles. -1The specific capacity of the battery using the unmodified separator is significantly lower, with a discharge specific capacity of 626.5 mAh g after 200 cycles of charge and discharge at 0.5 C. -1 .

Claims

1. A Co 0.5 Ni 0.5 The method for preparing a Te2 nanoparticle / three-dimensional carbon sheet composite material is characterized in that: The following steps are involved: (1) Preparation of three-dimensional carbon sheets Sodium citrate is calcined at high temperature in an inert atmosphere, and after being fully washed and dried, a three-dimensional carbon sheet skeleton is obtained; (2) Preparation of ZIF-67 nanoparticles / three-dimensional carbon sheets The three-dimensional carbon sheet skeleton was weighed and poured into a methanol solution containing cobalt nitrate. The mixture was stirred at room temperature and a methanol solution of 2-methylimidazole was added dropwise. The mixture was stirred evenly and allowed to stand. The mixture was washed and dried to obtain a ZIF-67 nanoparticle / three-dimensional carbon sheet composite. (3) Preparation of CoNi-LDH / 3D carbon sheet precursor The ZIF-67 / three-dimensional carbon sheet composite was weighed and placed in an ethanol solution of nickel nitrate, heated under reflux, stirred for several minutes, washed and dried to obtain a cobalt nickel double hydroxide CoNi-LDH / three-dimensional carbon sheet precursor; (4) Co 0.5 Ni 0.5 Preparation of Te2 Nanoparticles / Three-Dimensional Carbon Sheet Composites Weigh the CoNi-LDH / three-dimensional carbon sheet precursor and tellurium powder, stir and mix them evenly, and calcine them to obtain Co 0.5 Ni 0.5 Te2 nanoparticle / three-dimensional carbon sheet composite material.

2. The preparation method according to claim 1, characterized in that In step (1), the high-temperature calcination is sintering at a temperature of 700-900°C for 1-3 hours; and the inert atmosphere is Ar gas.

3. The preparation method according to claim 1, characterized in that In step (2), the ratio of the three-dimensional carbon sheet skeleton to the cobalt nitrate solution is 0.10-0.20 g:80 mL.

4. The preparation method according to claim 1 or 3, characterized in that In step (2), the concentration of the methanol solution of cobalt nitrate is 0.03 mol / L~0.06 mol / L; the concentration of the methanol solution of 2-methylimidazole is 0.12 mol / L~0.24 mol / L; and the volume ratio of the methanol solution containing cobalt nitrate to the methanol solution of 2-methylimidazole is 1:

1.

5. The preparation method according to claim 1, 3 or 4, characterized in that: In step (2), the stirring time is 3 to 12 hours; the standing time is 12 to 24 hours.

6. The preparation method according to claim 1, characterized in that In step (3), the concentration of the ethanol solution containing nickel nitrate is 0.015 mol / L~0.02 mol / L; the ratio of the ZIF-67 / three-dimensional carbon sheet composite to the nickel nitrate solution is 0.1~0.2 g:30-35 mL.

7. The preparation method according to claim 1 or 6, characterized in that In step (3), the heating reflux temperature is 70-90°C, and the heating reflux stirring time is 4-8 minutes.

8. The preparation method according to claim 1, characterized in that In step (4), the mass ratio of the CoNi-LDH / three-dimensional carbon sheet precursor to tellurium powder is 1:1.2~1.

5.

9. The preparation method according to claim 1 or 8, characterized in that In step (4), the calcination is carried out by heating the temperature to 600-800°C at a heating rate of 2°C per minute and maintaining the temperature for 3-5 hours.

10. A Co prepared by the preparation method according to any one of claims 1 to 9 0.5 Ni 0.5 Application of Te2 nanoparticle / three-dimensional carbon sheet composites as functional coating materials for lithium-sulfur battery separators.

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