Method for preparing metal sulfide ultrathin nanosheets in one step and application thereof

Abstract

The application relates to a one-step method for preparing metal sulfide ultrathin nanosheets and application, which comprises the following steps: step one: uniformly mixing a metal salt, a salt template agent and thiourea in ethanol to obtain a precursor mixed liquid; step two: performing heating and drying on the precursor mixed liquid to obtain a precursor powder; step three: performing heat treatment on the dried precursor powder; and step four: soaking the heat-treated precursor powder in deionized water, and then performing cleaning and drying to obtain a metal powder, namely the metal sulfide ultrathin nanosheet. The method for preparing the metal sulfide ultrathin nanosheet provided by the application does not need to additionally introduce a sulfur source, is simple and easy to operate, has low cost, and the obtained metal sulfide two-dimensional ultrathin nanosheet has uniform morphology, can provide a larger specific surface area, abundant energy storage sites and a shorter diffusion distance, and has great application prospects in the field of alkali metal ion batteries-potassium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a one-step method for preparing ultrathin metal sulfide nanosheets and its application. Background Technology

[0002] In recent years, transition metal materials, including sulfides, phosphides, and nitrides, have received widespread attention and reports. Due to their abundant reserves, low cost, and unique physicochemical properties, transition metals are widely used in energy conversion and storage, catalysis, and other fields. Among them, transition metal sulfides are the most attractive due to their high conductivity, excellent durability, and superior performance. Several transition metal sulfides with good electrochemical properties have been reported, including CoS2, NiS, CuS, and MoS2.

[0003] However, transition metal sulfides typically require chemical vapor deposition (CVD) with an external sulfur source (sulfur powder) to complete the sulfidation process. The amount of sulfur source and its distance from the heating center significantly affect the material's phase composition, making precise control of the metal sulfide composition difficult and increasing the experimental steps and complexity. Furthermore, sulfur powder is flammable and explosive, posing a significant safety hazard.

[0004] On the other hand, when metal sulfides are used as anodes in alkali metal ion batteries, they generally suffer from insufficient quantity and quality of exposed energy storage sites and low specific surface area, limiting their electrochemical performance. Two-dimensional structures can significantly increase the specific surface area of ​​materials, shorten ion diffusion paths, and expose energy storage sites, making them a common structure in the energy storage field. However, the preparation of two-dimensional non-layered metal sulfides is quite difficult, and currently, they are mostly prepared through coating or liquid-phase methods. Coating methods require sophisticated equipment and are costly; while liquid-phase methods usually require the addition of surfactants, which are difficult to completely remove, reducing the quality of the two-dimensional material. Therefore, further in-depth research is needed on the preparation methods of two-dimensional metal sulfides. Summary of the Invention

[0005] The purpose of this invention is to provide a one-step method for preparing metal sulfide ultrathin nanosheets and its application in order to solve the above-mentioned problems.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] This invention provides a one-step method for preparing metal sulfide ultrathin nanosheets, comprising the following steps:

[0008] Step 1: Mix the metal salt, salt template agent, and thiourea in ethanol until homogeneous to obtain a precursor mixture liquid;

[0009] Step 2: Heat and dry the precursor mixture to obtain precursor powder;

[0010] Step 3: Heat treat the dried precursor powder;

[0011] Step 4: Soak the heat-treated precursor powder in deionized water, then wash and dry it to obtain metal powder, which is the metal sulfide ultrathin nanosheet.

[0012] As a further optimization of the present invention, the metal salt includes, but is not limited to, chloride salts, nitrate salts, and acetylacetone salts.

[0013] As a further optimization of the present invention, the salt template agent includes, but is not limited to, sodium chloride, potassium chloride, and potassium carbonate.

[0014] As a further optimization of the present invention, the mass ratio of the metal salt to the salt template agent is 1:10 to 1000; the molar ratio of the metal salt to thiourea is 1:1 to 50.

[0015] As a further optimization of the present invention, in step three, the heat treatment temperature is 500-900℃, the reaction time is 1-10h, and the reaction atmosphere is at least one or more mixed gases selected from nitrogen, hydrogen, argon, and ammonia.

[0016] The present invention also provides a metal sulfide ultrathin nanosheet prepared by any of the methods described above.

[0017] The present invention also provides an application of the metal sulfide ultrathin nanosheets as described above in the field of alkali metal ion batteries, wherein the alkali metal ion battery is a potassium ion battery, and the metal sulfide ultrathin nanosheets serve as the negative electrode material of the potassium ion battery.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) The method for preparing metal sulfide ultrathin nanosheets provided by the present invention does not require the introduction of an additional sulfur source, is simple to operate, and has low cost. The morphology and structure of the obtained metal sulfide are two-dimensional ultrathin nanosheets with uniform morphology, which can provide a large specific surface area, abundant energy storage sites and shorter diffusion distance, showing great application prospects in the field of alkali metal ion battery-potassium ion battery.

[0020] (2) The present invention found that when potassium carbonate is selected as the salt template agent, the ultrathin MoS2 nanosheets prepared can exhibit excellent potassium storage performance when used as the negative electrode material of potassium-ion battery.

[0021] (3) The present invention found that different heat treatment methods affect the performance of the prepared metal sulfide ultrathin nanosheets as negative electrodes in potassium-ion batteries. The heat treatment method adopted is to raise the temperature to 300°C in the first stage at a heating rate of 10°C / min and to 600°C in the second stage at a heating rate of 5°C / min. After 200 cycles of battery operation, it can still maintain a high reversible potassium storage specific capacity and coulombic efficiency, showing excellent reversible capacity and long cycle life. Attached Figure Description

[0022] Figure 1 The ultrathin Cu provided in Embodiment 1 of the present invention 1.95 X-ray diffraction pattern of S nanosheets;

[0023] Figure 2 The ultrathin Cu provided in Embodiment 1 of the present invention 1.95 Scanning electron microscope image of S nanosheets;

[0024] Figure 3 The X-ray diffraction pattern of the ultrathin MoS2 nanosheets provided in Example 2 of this invention;

[0025] Figure 4 This is a scanning electron microscope image of the ultrathin MoS2 nanosheets provided in Embodiment 2 of the present invention;

[0026] Figure 5 Cycling curves of the ultrathin MoS2 nanosheets provided in Example 3 of the present invention when operating at a current density of 0.1 A / g;

[0027] Figure 6 The ultrathin Cu provided in Embodiment 4 of the present invention 1.95 Cycling curves of S nanosheets operating at a current density of 0.1 A / g. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0029] Example 1

[0030] (1) Weigh 1 mmol of copper acetylacetone and 5 mmol of thiourea, dissolve them in 60 mL of ethanol, then add 30 g of sodium chloride powder and stir vigorously for 48 hours.

[0031] (2) Place the stirred liquid in a heating plate and dry it at 90°C to obtain precursor powder;

[0032] (3) After thoroughly grinding the precursor powder, transfer it to a ceramic crucible and place it in the center of a tube furnace for heat treatment under a nitrogen atmosphere. The heating rate is 5℃ / min, the temperature is 600℃, the holding time is 2 hours, and the mixture is allowed to cool naturally after the reaction is complete.

[0033] (4) Immerse the sample obtained in (3) in excess deionized water until sodium chloride is completely dissolved, then filter it, wash it 3 to 5 times with deionized water and ethanol, put the washed precipitate into an oven and dry it at 60°C for 12 hours.

[0034] The ultrathin Cu prepared in this embodiment 1.95 X-ray diffraction pattern of S nanosheets ( Figure 1 ), with Cu 1.95 Corresponding to PDF card (89-2072) of S, this indicates that the method provided by the present invention can achieve one-step preparation of copper sulfide. The ultrathin Cu prepared in this embodiment... 1.95 Scanning electron microscope images of S nanosheets ( Figure 2 It exhibits a two-dimensional sheet-like structure.

[0035] Example 2

[0036] (1) Weigh 1 mmol of molybdenum acetylacetonate and 5 mmol of thiourea, dissolve them in 60 mL of ethanol, and then add 30 g of sodium chloride powder. Stir vigorously for 48 hours;

[0037] (2) Place the stirred liquid on a heating plate and dry it at 90°C to obtain precursor powder;

[0038] (3) After the precursor powder is fully ground, it is transferred to a ceramic crucible and placed in the center of a tube furnace. It is then heat-treated under a nitrogen atmosphere at a heating rate of 10℃ / min, a temperature of 800℃, and a holding time of 2 hours. After the reaction is completed, it is allowed to cool down naturally.

[0039] (4) Immerse the sample obtained in (3) in excess deionized water until sodium chloride is completely dissolved, then filter it, wash it with deionized water and ethanol 3 to 5 times, put the washed precipitate into an oven and dry it at 60°C for 12 hours to obtain metal powder, which is the metal sulfide ultrathin nanosheet.

[0040] X-ray diffraction pattern of ultrathin MoS2 nanosheets prepared in Example 2 ( Figure 3 The image corresponds to the PDF card (87-2416) of MoS2 in the 2H phase, indicating that the method provided in this embodiment can achieve one-step preparation of molybdenum disulfide. The scanning electron microscope image of the ultrathin MoS2 nanosheets prepared in Example 2 is shown. Figure 4 The structure exhibits an ultrathin two-dimensional nanosheet structure.

[0041] Example 3

[0042] Based on Example 2, three groups of MoS2 ultrathin nanosheets were prepared by selecting different types of salt template agents, sodium chloride, potassium chloride, and potassium carbonate. In addition, ultrathin two-dimensional MoS2 nanosheets prepared by chemical vapor deposition were used as a control group.

[0043] Specifically, using S powder and MoS3 powder as raw materials, ultrathin MoS2 nanosheets are grown on a Si / SiO2 substrate (SiO2 thickness 300nm). The process flow is as follows:

[0044] (1) The substrate was ultrasonically cleaned for 15 minutes in sequence with acetone, ethanol and deionized water, and then dried with nitrogen.

[0045] (2) Use a quartz support to load the substrate and 0.03g of MoS3 powder and place it in the constant temperature zone of the furnace tube. The distance between the constant temperature zone and the furnace tube inlet is 43cm. The SiO2 of the two substrates are placed face to face with a spacing of 2mm, and the MoS3 powder is piled on the lower substrate.

[0046] (3) Load 1.5g of S powder into an alumina boat and feed it into the furnace tube 25cm from the inlet. After placing the reactants and substrate, seal the furnace tube.

[0047] (4) Evacuate the furnace tube to 5 Pa, close the vacuum valve, and introduce argon gas until the furnace tube returns to normal pressure. Repeat the above process three times to ensure that the air inside the furnace tube is completely replaced by argon gas. Adjust the argon gas flow rate to 100 cm³ / h. 3 The temperature of the isothermal zone was increased to 650℃ at a heating rate of 15℃ / min. After reacting for 30 minutes, the temperature was naturally cooled to room temperature. The substrate was then removed, and the thin film formed on the substrate was the ultrathin MoS2 nanosheet.

[0048] The four groups of MoS2 ultrathin nanosheets were mixed with acetylene black and PVDF in a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone solvent was added dropwise. The mixture was stirred thoroughly until a uniform slurry was formed. The slurry was then spread on the surface of a copper foil, coated with a film using a doctor blade, and then vacuum dried. The dried copper foil was cut into discs with a diameter of 16 micrometers, transferred to a glove box, and packaged into CR2032 coin-type potassium-ion batteries. When the MoS2 anode operated at a current density of 0.1 A / g, after 100 cycles, its reversible potassium storage specific capacity and coulombic efficiency were calculated. The results are shown in Table 1.

[0049] Table 1. Results Statistics Table

[0050]

[0051] As can be seen from the results in Table 1, the method provided in this embodiment can maintain a similar reversible potassium storage specific capacity and coulombic efficiency compared with the chemical vapor deposition method used in the control group. The method adopted in this embodiment has the advantages of simpler experimental procedure, simpler operation and lower cost compared with the chemical vapor deposition method used in the control group.

[0052] Furthermore, when ultrathin MoS2 nanosheets prepared using potassium carbonate as the salt template agent are used as anode materials for potassium-ion batteries, even after 100 cycles at a current density of 0.1 A / g, their reversible potassium storage capacity remains as high as 263 mAh / g, and the coulombic efficiency is close to 99%. Figure 5 It exhibits excellent potassium storage performance.

[0053] Example 4

[0054] (1) Weigh 1 mmol of copper acetylacetone and 5 mmol of thiourea, dissolve them in 60 mL of ethanol, then add 30 g of sodium chloride powder and stir vigorously for 48 hours.

[0055] (2) Place the stirred liquid in a heating plate and dry it at 90°C to obtain precursor powder;

[0056] (3) After the precursor powder is fully ground, it is transferred to a ceramic crucible and placed in the center of a tube furnace. It is then heat-treated under a nitrogen atmosphere for 2 hours. The heat treatment process is set as shown in Table 2. After the reaction is completed, the temperature is naturally lowered.

[0057] (4) Immerse the sample obtained in (3) in excess deionized water until sodium chloride is completely dissolved, then filter it, wash it 3 to 5 times with deionized water and ethanol, put the washed precipitate into an oven and dry it at 60°C for 12 hours.

[0058] The obtained 3 groups of Cu 1.95 S-type ultrathin nanosheets were mixed with acetylene black and PVDF in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone solvent was added dropwise, and the mixture was stirred thoroughly until a uniform slurry was formed. The slurry was then spread onto a copper foil surface, coated using a doctor blade, and then vacuum dried. The dried copper foil was cut into 16-micrometer diameter discs, transferred to a glove box, and encapsulated into CR2032 coin-type potassium-ion batteries. 1.95 When the S anode operates at a current density of 0.1 A / g, its reversible potassium storage specific capacity and coulombic efficiency are calculated after 100 and 200 cycles, and the results are shown in Table 2.

[0059] Table 2. Results Statistics Table

[0060]

[0061] First, in Table 2, the Cu obtained in group 4 1.95 When the S-type negative electrode operates at a current density of 0.1 A / g, even after 100 cycles, its reversible potassium storage capacity remains as high as 159.2 mAh / g, with a coulombic efficiency approaching 100% (battery cycle reversibility), demonstrating excellent capacity retention. Figure 6 ).

[0062] Different heat treatment methods affect the performance of the prepared metal sulfide ultrathin nanosheets as a negative electrode in potassium-ion batteries. As shown in Table 2, compared with group 4, the two-stage heating heat treatment method for the precursor powder in groups 5 and 6 has a positive effect on improving the reversible potassium storage specific capacity and coulombic efficiency. In addition, comparing groups 5 and 6, it can be seen that the heat treatment method with a first stage heating rate of 10℃ / min to 300℃ and a second stage heating rate of 5℃ / min to 600℃ can still maintain a high reversible potassium storage specific capacity and coulombic efficiency after 200 battery working cycles, showing excellent reversible capacity and long cycle life.

[0063] The foregoing description illustrates and describes several preferred embodiments of the invention. However, as previously stated, it should be understood that the invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the invention should be within the protection scope of the appended claims.

Claims

1. The application of a metal sulfide ultrathin nanosheet in a potassium-ion battery, characterized in that, The metal sulfide ultrathin nanosheets serve as the negative electrode material for potassium-ion batteries. The method for preparing the metal sulfide ultrathin nanosheets includes the following steps: Step 1: Mix 1 mmol of copper acetylacetonate, 30 g of sodium chloride powder, and 5 mmol of thiourea in ethanol until homogeneous to obtain a precursor mixture liquid; Step 2: Heat and dry the precursor mixture to obtain precursor powder; Step 3: Heat treatment is performed on the dried precursor powder under a nitrogen atmosphere. The heat treatment adopts the following method: the first stage heating rate is 10℃ / min, the temperature is raised to 300℃, the second stage heating rate is 5℃ / min, the temperature is raised to 600℃, and the holding time is 2 hours. Step 4: Immerse the heat-treated precursor powder in deionized water, then wash and dry to obtain metal powder, which is the metal sulfide ultrathin nanosheet, wherein the metal sulfide ultrathin nanosheet is Cu. 1.95 S-type ultrathin nanosheets.

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