Two-dimensional transition metal chalcogenide nanosheet as well as preparation method and application thereof in field of wide-temperature-range energy storage electrode materials of sodium-ion batteries
The preparation of two-dimensional transition metal chalcogenide nanosheets with a 1T phase structure through high-temperature sintering and lithiation reactions is solved, and the capacity attenuation and conductivity of two-dimensional transition metal chalcogenide nanosheets in sodium ion batteries is improved, the electronic conductivity and energy storage performance are improved, and the fast charging of wide-temperature sodium ion batteries is achieved.
Patent Information
- Application Number
- CN202510488784.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-18
- Publication Date
- 2025-07-18
AI Technical Summary
Two-dimensional transition metal chalcogenide nanosheets have problems such as fast capacity decay, poor conductivity, enhanced kinetics of energy storage performance and poor stability in sodium ion batteries.
By sintering transition metal element and chalcogen elemental powder at high temperature, lithiation reaction with metal lithium after ultrasonic centrifugation, forming a two-dimensional transition metal chalcogenide nanosheet with a symmetrical phase structure of 1 T phase and a triangular lattice arrangement.
It improves electronic conductivity and energy storage performance, enhances the structural stability of the embedded and disengagement process of sodium ions, and realizes the fast charging performance of wide-temperature sodium ion batteries.
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Figure CN120328494A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of battery materials, and in particular, to two-dimensional transition metal chalcogenide nanosheets, a preparation method thereof, and an application in the field of sodium-ion battery wide-temperature energy storage electrode materials. Background Art
[0002] Two-dimensional transition metal chalcogenide (TMDs) nanosheets, with the basic chemical formula MX2, are compounds formed by transition metals (M such as Re, Mo, W, Ti or V) and chalcogen elements (X such as S, Se, Te), and can be applied as electrode materials for batteries. Two-dimensional MX2 electrode materials have become a popular research object in the field of sodium-ion battery energy storage due to their large specific surface area, abundant active sites, and short ion diffusion channels. However, such materials still face many challenges in practical applications. First, the bulk materials will undergo volume changes during the battery cycling process, resulting in slow ion diffusion kinetics and increased strain, thereby causing rapid capacity decay. Second, the natural formation states of most MX2, such as the trigonal prismatic phase (2H phase) and the one-dimensional distorted octahedral phase (1T' phase), are semiconductors, which limits the electronic conductivity of the materials. In addition, the small interlayer spacing of MX2 is not conducive to the rapid diffusion and insertion of ions, restricting the kinetic improvement of energy storage performance.
[0003] During the preparation of the anode material for sodium-ion batteries, the random re-stacking of two-dimensional nanosheets will cause stability problems, which have an adverse effect on the infiltration and cycling stability of the electrolyte. Summary of the Invention
[0004] The problem solved by the present invention is how to solve the problems of rapid capacity decay, poor conductivity, restricted kinetic improvement of energy storage performance, and poor stability of two-dimensional transition metal chalcogenide nanosheets.
[0005] To solve the above problems, the present invention provides two-dimensional transition metal chalcogenide nanosheets, a preparation method thereof, and an application in the field of sodium-ion battery wide-temperature energy storage electrode materials.
[0006] In the first aspect, the present invention provides a preparation method of two-dimensional transition metal chalcogenide nanosheets, comprising the following steps:
[0007] S1: Take a transition metal elemental powder and a chalcogen elemental powder, mix them evenly, heat up to 700 to 1100 °C and keep warm for more than 72 hours, and then cool to room temperature to obtain a 1T' phase or 2H phase two-dimensional transition metal chalcogenide;
[0008] S2: Add the 1T' phase two-dimensional transition metal chalcogenide into a mixed solution formed by water and ethanol, ultrasonicate for 2 to 4 hours, centrifuge and take the supernatant to obtain exfoliated 1T' phase or 2H phase two-dimensional transition metal chalcogenide nanosheets;
[0009] S3: Under an inert gas environment, the exfoliated 1T'-phase or 2H-phase or -phase two-dimensional transition metal chalcogenide nanosheets are mixed with metallic lithium to undergo a lithiation reaction, and then added to a mixed solution formed by water and ethanol for washing. After centrifugation, the supernatant is taken to obtain 1T-phase two-dimensional transition metal chalcogenide nanosheets with a symmetric phase structure of the 1T phase and a morphology presenting a triangular lattice arrangement.
[0010] Optionally, step S1 includes: The transition metal elemental powder and the chalcogen elemental powder with a molar ratio of 1:2 are thoroughly ground and mixed evenly in a mortar, sealed in a quartz tube under vacuum conditions, and heated to 700 to 1100 °C at a heating rate of 1 to 2 °C per minute for insulation.
[0011] Optionally, the power of the ultrasonic wave is 800 to 1000 W, and the rotation speed of the centrifugation is 300 to 4000 rpm.
[0012] Optionally, step S3 includes: The exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets are mixed with metallic lithium and loaded into a quartz tube. Ammonia gas is introduced into the quartz tube, and it is immersed in a liquid nitrogen bath to undergo a lithiation reaction. The sign of the reaction process is that the liquid color gradually changes from blue to light blue and then to colorless, indicating the end of the lithiation reaction.
[0013] Optionally, after the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets and metallic lithium are loaded into the quartz tube, ammonia gas is introduced into and discharged from the quartz tube multiple times to wash the inside of the quartz tube and remove the air and impurities inside the quartz tube.
[0014] Optionally, step S3 further includes: After the lithiation reaction ends, the liquid ammonia is vaporized at room temperature.
[0015] Optionally, according to the method for preparing two-dimensional transition metal chalcogenide nanosheets in claim 4, the molar ratio of the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets to metallic lithium is 1:5.
[0016] Optionally, the inert gas environment is an argon environment or a helium environment.
[0017] In a second aspect, the present invention provides a two-dimensional transition metal chalcogenide nanosheet, which is prepared by using the method for preparing two-dimensional transition metal chalcogenide nanosheets described in any one of the above, and the two-dimensional transition metal chalcogenide nanosheet has a symmetric phase structure of the 1T phase and a morphology presenting a triangular lattice arrangement.
[0018] In a third aspect, the present invention provides an application of the two-dimensional transition metal chalcogenide nanosheet described above in the field of sodium-ion battery wide-temperature-range energy storage electrode materials.
[0019] The beneficial effects of the two-dimensional transition metal chalcogenide nanosheets of the present invention, their preparation method, and their application in the field of sodium-ion battery wide-temperature energy storage electrode materials are as follows: sintering at a high temperature of 700 to 1100 °C to obtain 1T' phase or 2H phase two-dimensional transition metal chalcogenide. The 1T' phase is a distorted version generated after the displacement of the atoms of the transition metal, resulting in octahedral distortion of the phase and low crystal symmetry. The atoms of the transition metal in the 1T' phase two-dimensional transition metal chalcogenide nanosheets are arranged in a rhombic shape, forming a distorted octahedral structure. Therefore, the 1T' phase two-dimensional transition metal chalcogenide nanosheets are semiconductors, resulting in low electronic conductivity of the 1T' phase two-dimensional transition metal chalcogenide nanosheets. The trigonal prism coordination of the 2H phase leads to the splitting of d orbitals (such as the dominant occupation of the d2 2 orbital of Mo), forming a semiconductor energy band, resulting in low electronic conductivity of the 2H phase two-dimensional transition metal chalcogenide nanosheets; after ultrasonic centrifugation, 1T' phase or 2H phase two-dimensional transition metal chalcogenide nanosheets are obtained, and 1T phase two-dimensional transition metal chalcogenide nanosheets are obtained by forming vacancies in the chalcogenide through a lithiation reaction. They have longer metal-sulfur bonds (M-X bonds), exhibit a triangular lattice arrangement, and have metallicity. The increased interlayer spacing is beneficial for electron migration and ion diffusion, resulting in better electronic conductivity and energy storage performance of the 1T phase two-dimensional transition metal chalcogenide nanosheets, being beneficial for the structural stability of the sodium ion insertion and extraction processes, achieving fast charging of the wide-temperature sodium-ion battery, and can also be applied to low-temperature energy storage; and the lattice is stretched along the direction of the transition metal chain, the crystal structure symmetry is improved, and the structural stability and reaction kinetics are enhanced during the cycling process. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a flowchart of the preparation method of the two-dimensional transition metal chalcogenide nanosheets of the embodiment of the present invention;
[0021] Figure 2 It is an X-ray diffraction pattern of 1T' phase ReSe2 of Example 1;
[0022] Figure 3 In it, a is a transmission electron microscope image of 1T' phase ReSe2 of Example 1 with a resolution of 200 nm;
[0023] Figure 3 In it, b is a high-magnification transmission electron microscope image of 1T' phase ReSe2 of Example 1 with a resolution of 1 nm;
[0024] Figure 4 In it, a is an X-ray diffraction pattern of 1T' phase ReSe2 nanosheets and 1T phase ReSe2 nanosheets of Example 1;
[0025] Figure 4In Figure b is the Raman spectrum of the 1T'-phase ReSe2 nanosheets and 1T-phase ReSe2 nanosheets of Example 1;
[0026] Figure 5 In Figure a is the transmission electron microscope image of the 1T'-phase ReSe2 nanosheets of Example 1 with a resolution of 200 nm;
[0027] Figure 5 In Figure b is the transmission electron microscope image of the 1T-phase ReSe2 nanosheets of Example 1 with a resolution of 200 nm;
[0028] Figure 6 In Figure a is the high-magnification transmission electron microscope image of the 1T'-phase ReSe2 of Example 1 with a resolution of 1 nm;
[0029] Figure 6 In Figure b is the high-magnification transmission electron microscope image of the 1T-phase ReSe2 of Example 1 with a resolution of 1 nm;
[0030] Figure 7 is the sodium storage performance curve of the 1T-phase ReSe2 electrode and 1T'-phase ReSe2 electrode of Example 1 at 20 A / g at room temperature;
[0031] Figure 8 is the sodium storage performance curve of the 1T-phase ReSe2 electrode of Example 1 at 1 A / g at -40 °C;
[0032] Figure 9 is the energy storage performance curve of the 1T-phase ReSe2 electrode and 1T'-phase ReSe2 electrode of Example 1 at low temperature. Detailed Embodiments
[0033] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments described herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are only for exemplary purposes and are not used to limit the protection scope of the present invention.
[0034] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention;
[0035] The term "including" and its variations used in this document are open inclusions, i.e., "including but not limited to"; the term "based on" means "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments".
[0036] In the related art, two-dimensional MX2 electrode materials have become popular materials for sodium ion battery energy storage due to their large specific surface area, a large number of active sites and short ion diffusion channels. However, the volume change of its bulk material during the battery cycle leads to slow ion diffusion kinetics and large strain leads to rapid capacity decay. For most MX2, the naturally formed bulk triangular prism phase (2H phase) and one-dimensional distorted octahedral phase (1T' phase) are semiconductors, which limit electronic conductivity. In addition, the small interlayer spacing of MX2 leads to slow ion diffusion and embedding, which is not conducive to the kinetic improvement of its energy storage performance. In the process of preparing the negative electrode material of sodium ion battery, the random restacking of two-dimensional nanosheets causes stability-related problems, which is very unfavorable for the infiltration of electrolyte and cycle stability. Studies have shown that the intrinsic phase structure of two-dimensional MX2 can be changed by phase engineering design to obtain a metallic conductive phase with increased interlayer spacing and conducive to electron migration and ion diffusion; defect engineering and doping, strain engineering and heterostructure construction can design the structure and properties of MX2, thereby overcoming the above structural problems and improving its sodium storage performance. However, the samples obtained by these methods have low content of phase structure modulation and their application in fast charging of sodium-ion batteries with a wide temperature range is limited.
[0037] In view of the problems existing in the above-mentioned related technologies, this embodiment provides two-dimensional transition metal chalcogenide nanosheets and a preparation method thereof and their application in the field of wide temperature range energy storage electrode materials for sodium ion batteries.
[0038] like Figure 1 As shown, a method for preparing a two-dimensional transition metal chalcogenide nanosheet provided in an embodiment of the present invention comprises the following steps:
[0039] S1: Take a transition metal powder and a chalcogen powder and mix them evenly, heat them to 700 to 1100°C and keep them warm for more than 72 hours, and cool them to room temperature to obtain a 1T' phase or 2H phase two-dimensional transition metal chalcogenide;
[0040] S2: adding the 1T' phase two-dimensional transition metal chalcogenide to a mixed solution of water and ethanol and ultrasonicating for 2 to 4 hours, and taking the supernatant by centrifugation to obtain the exfoliated 1T' phase or 2H phase two-dimensional transition metal chalcogenide nanosheets;
[0041] S3: Under an inert gas environment, the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets are mixed with metallic lithium for a lithiation reaction, and then added to a mixed solution formed by water and ethanol for cleaning. After centrifugation, the supernatant is taken to obtain 1T-phase two-dimensional transition metal chalcogenide nanosheets with a symmetric phase structure of the 1T phase and a triangular lattice arrangement morphology.
[0042] In this embodiment, the 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide is sintered at a high temperature of 700 to 1100 °C. The 1T'-phase is a distorted version generated after the displacement of the atoms of the transition metal, resulting in an octahedral distortion of the phase and low crystal symmetry. The atoms of the transition metal in the 1T'-phase two-dimensional transition metal chalcogenide nanosheets are arranged in a rhombic shape, forming a distorted octahedral structure, which is a semiconductor, resulting in relatively low electronic conductivity of the 1T'-phase two-dimensional transition metal chalcogenide nanosheets. The trigonal prism coordination of the 2H-phase causes the splitting of d orbitals (such as the d2 2 orbital dominates), forming a semiconductor energy band, resulting in relatively low electronic conductivity of the 2H-phase two-dimensional transition metal chalcogenide nanosheets. After ultrasonic centrifugation, 1T'-phase two-dimensional transition metal chalcogenide nanosheets are obtained. By using a lithiation reaction to form vacancies in the chalcogenide, 1T-phase two-dimensional transition metal chalcogenide nanosheets are obtained, which have longer metal-sulfur bonds (M-X bonds), exhibit a triangular lattice arrangement, and have metallicity. The increased layer spacing is beneficial for electron migration and ion diffusion, resulting in better electronic conductivity and energy storage performance of the 1T-phase two-dimensional transition metal chalcogenide nanosheets, which is beneficial for the structural stability of the sodium ion insertion and extraction processes, enabling fast charging of the wide-temperature-range sodium-ion battery, and it can also be applied to low-temperature energy storage. And the lattice is stretched along the direction of the transition metal chain, improving the crystal structure symmetry and enhancing the structural stability and reaction kinetics during the cycling process.
[0043] Optionally, step S1 includes: The transition metal elemental powder and the chalcogen elemental powder with a molar ratio of 1:2 are thoroughly ground and mixed evenly in a mortar, sealed in a quartz tube under vacuum conditions, and heated to 700 to 1100 °C at a heating rate of 1 to 2 °C per minute for insulation.
[0044] In this alternative embodiment, the transition metal elemental powder and the chalcogen elemental powder with a molar ratio of 1:2 are thoroughly ground in a mortar to ensure the uniformity of the powder; they are sealed in a quartz tube under vacuum conditions and heated to 700 to 1100 °C at a heating rate of 1 to 2 °C per minute for heat preservation. This step ensures the full progress of the reaction by controlling the heating rate and heat preservation conditions, thereby obtaining a uniform 1T' phase or 2H phase two-dimensional transition metal chalcogenide and solving the problem of uneven mixing during the preparation of two-dimensional transition metal chalcogenide nanosheets. Compared with the prior art, this application ensures the uniformity and purity of the final product by controlling the molar ratio of the reactants, the grinding uniformity, and the heating and heat preservation conditions, which not only improves the controllability of the preparation process but also enhances the performance of the final product.
[0045] Specifically, the grinding process can be achieved by mechanical grinding or ball milling, etc., the vacuum sealing can be realized by a vacuum pump, and the heating and heat preservation can be completed by a program-controlled electric furnace.
[0046] Optionally, the power of the ultrasound is 800 to 1000 W, and the rotation speed of the centrifugation is 300 to 4000 rpm.
[0047] In this alternative embodiment, the exfoliation and dispersion process of the nanosheets is optimized by specifically specifying the ultrasound power and the centrifugation rotation speed. The ultrasound power is between 800 and 1000 W, which can provide sufficient energy to effectively exfoliate the nanosheets while avoiding the damage of the nanosheets caused by too high power. The centrifugation rotation speed is between 300 and 4000 rpm. The exfoliated nanosheets are separated from the impurities in the solution by appropriate centrifugal force to ensure a pure nanosheet supernatant. The optimized combination of the two parameters improves the exfoliation effect of the nanosheets, helps to improve the quality and dispersibility of the nanosheets, and thus enhances their performance as the anode material in sodium-ion batteries.
[0048] Specifically, after centrifugation, the upper clear liquid can be sucked out with a pipette.
[0049] Specifically, the range of the ultrasound power is 800 to 1000 W, which can be achieved by adjusting the output power of the ultrasound device.
[0050] Specifically, the ultrasound device can include a controller with adjustable power, and the user can set the required power value according to the need. The range of the centrifugation rotation speed is 300 to 4000 rpm, which can be achieved by adjusting the rotation speed controller of the centrifuge. The centrifuge is usually equipped with a control panel with adjustable rotation speed, and the user can set the required rotation speed value according to the specific experimental requirements.
[0051] Optionally, step S3 includes: mixing the exfoliated 1T' phase or 2H phase two-dimensional transition metal chalcogenide nanosheets with metallic lithium and loading them into a quartz tube, introducing ammonia gas into the quartz tube, immersing it in a liquid nitrogen bath, and undergoing a lithiation reaction. The sign of the reaction progress is that the liquid color gradually changes from blue to light blue and then to colorless, indicating the end of the lithiation reaction.
[0052] In this optional embodiment, the lithiation reaction monitors the reaction progress through the gradual change of the liquid color to ensure precise control of the lithiation reaction, thereby obtaining 1T phase two-dimensional transition metal chalcogenide nanosheets with a symmetric phase structure and a triangular lattice arrangement morphology. Thus, the problem of difficult precise control of the reaction progress during the lithiation reaction is solved. By introducing ammonia gas and combining with the operation of the liquid nitrogen bath, a stable reaction environment is provided. Combining with the method of monitoring the reaction progress through color change, precise control of the lithiation reaction is achieved, avoiding over-lithiation or under-lithiation reactions. Compared with the prior art, the technical solution of this application has significant advantages in the accuracy and operability of reaction control, can effectively avoid over-lithiation or under-lithiation reactions, and thus improves the quality and consistency of the final product. The 1T phase two-dimensional transition metal chalcogenide nanosheets obtained by this method have a symmetric phase structure and a triangular lattice arrangement morphology, showing excellent physical and chemical properties, and are suitable for the development and application of various energy storage materials.
[0053] Further, after the exfoliated 1T' phase or 2H phase two-dimensional transition metal chalcogenide nanosheets and metallic lithium are loaded into the quartz tube, ammonia gas is introduced into and discharged from the quartz tube multiple times to wash the inside of the quartz tube and remove the air and impurities inside the quartz tube.
[0054] In this optional embodiment, ammonia gas, as an effective cleaning gas, can effectively wash the inside of the quartz tube by introducing and discharging ammonia gas into the quartz tube multiple times, thereby removing the air and impurities inside the quartz tube. This operation ensures a pure environment for the lithiation reaction, helps improve the reaction efficiency and product purity, and thus provides a impurity-free environment for the subsequent lithiation reaction. This process can be achieved by automated equipment to ensure the repeatability and consistency of the operation. Further, the number of times of introduction and discharge can be adjusted according to actual needs to achieve the best cleaning effect. Compared with the prior art, the technical solution of this application provides a simple and effective cleaning method, solves the problem of air and impurity residues inside the quartz tube, and has high practical value.
[0055] Optionally, step S3 further includes: vaporizing liquid ammonia at room temperature after the lithiation reaction ends.
[0056] In this alternative embodiment, the step of vaporizing liquid ammonia at room temperature is to process the remaining liquid ammonia. The function of this technical feature is to avoid the residue of liquid ammonia by vaporizing it, thus ensuring that the subsequent processing process will not be affected by liquid ammonia. In this way, the problem of liquid ammonia after the lithiation reaction can be effectively processed, ensuring the safety and stability of the entire preparation process. Compared with the prior art, this method is simple and effective, does not require complex equipment and operations, and avoids the interference of liquid ammonia on subsequent processing steps, improving the reliability and controllability of the preparation process.
[0057] Specifically, the vaporization of liquid ammonia can be carried out by natural evaporation, or the vaporization can be accelerated by heating or increasing the air flow. Specifically, the reaction mixture can be placed in a well-ventilated environment to allow liquid ammonia to evaporate naturally; or it can be heated to a temperature slightly higher than room temperature to accelerate the vaporization process of liquid ammonia. In addition, the evaporation of liquid ammonia can be accelerated by introducing an inert gas, such as nitrogen or argon, into the reaction vessel. As a preferred embodiment, after the reaction is completed, the reaction vessel can be placed in a fume hood to process liquid ammonia by natural evaporation.
[0058] Optionally, according to the method for preparing two-dimensional transition metal chalcogenide nanosheets of claim 4, characterized in that the molar ratio of the exfoliated 1T' phase or 2H phase two-dimensional transition metal chalcogenide nanosheets to metallic lithium is 1:5.
[0059] In this alternative embodiment, by setting the molar ratio of the 1T’ phase or 2H phase two-dimensional transition metal chalcogenide nanosheets to metallic lithium to 1:5, the full progress of the lithiation reaction can be ensured, so as to obtain 1T phase two-dimensional transition metal chalcogenide nanosheets with a symmetric phase structure of 1T phase and a morphology presenting triangular lattice arrangement. The obtained 1T phase two-dimensional transition metal chalcogenide nanosheets not only have excellent structure and morphology, improving the electrical conductivity and energy storage performance of the material, but also can significantly improve its performance and stability in the field of anode materials for sodium-ion batteries, and thus have high application value.
[0060] Optionally, the environment of the inert gas is an argon environment or a helium environment.
[0061] In this alternative embodiment, the use of an argon or helium environment can effectively avoid adverse reactions of the material with oxygen or other reactive gases in the air during the preparation process, thus maintaining the purity and structural stability of the material. By carrying out the reaction in an argon or helium environment, it can be ensured that the finally obtained two-dimensional transition metal chalcogenide nanosheets have a symmetric phase structure of 1T phase and a morphology presenting triangular lattice arrangement. This specific phase structure and morphology contribute to improving the electronic conductivity and ion diffusion performance of the material, thereby enhancing its application performance in anode materials for sodium-ion batteries.
[0062] Specifically, argon and helium, as inert gases, do not undergo chemical reactions with other substances at high temperatures and can provide a stable and pollution-free reaction environment. Such an environment is crucial for maintaining the structural integrity and purity of materials. As a preferred embodiment, an argon environment is commonly widely used due to its lower cost and ease of access, while a helium environment can be used when higher purity requirements are needed.
[0063] A two-dimensional transition metal chalcogenide nanosheet provided by an embodiment of the present invention is prepared by using the preparation method of the two-dimensional transition metal chalcogenide nanosheet described in any one of the above. The two-dimensional transition metal chalcogenide nanosheet has a symmetric phase structure of the 1T phase and a morphology presenting a triangular lattice arrangement.
[0064] In this embodiment, the two-dimensional transition metal chalcogenide nanosheet obtains a symmetric phase structure of the 1T phase and a morphology of a triangular lattice arrangement through a specific preparation method. Such structural features help to increase the interlayer spacing, improve the electron migration ability and ion diffusion performance, thereby overcoming problems such as slow ion diffusion kinetics and limited electron conductivity in the application of two-dimensional MX2 electrode materials as anode materials for sodium-ion batteries. At the same time, the morphology of the triangular lattice arrangement can enhance the structural stability of the material and reduce problems such as capacity attenuation and poor cycle stability caused by volume changes. Through this technical solution, the wide-temperature-range energy storage performance and application range of sodium-ion batteries can be effectively improved.
[0065] The application of the two-dimensional transition metal chalcogenide nanosheet of the present application in the field of anode materials for wide-temperature-range energy storage of sodium-ion batteries has significant advantages compared with the prior art. First, the 1T phase structure and the morphology of the triangular lattice arrangement obtained through a specific preparation method help to improve the electron migration ability and ion diffusion performance, thereby overcoming the problems of slow ion diffusion kinetics and limited electron conductivity existing in the prior art. Second, such structural features can enhance the structural stability of the material and reduce problems such as capacity attenuation and poor cycle stability caused by volume changes. Therefore, the technical solution of the present application can significantly improve the energy storage performance and cycle life of sodium-ion batteries.
[0066] An application of a two-dimensional transition metal chalcogenide nanosheet as described above provided by an embodiment of the present invention in the field of anode materials for wide-temperature-range energy storage of sodium-ion batteries.
[0067] In this embodiment, the two-dimensional transition metal chalcogenide nanosheet is characterized by having a symmetric phase structure of the 1T phase and presenting a morphology of triangular lattice arrangement. This structure helps to improve its performance as an anode material for sodium-ion batteries. By adopting a specific preparation method, 1T-phase two-dimensional transition metal chalcogenide nanosheets with excellent electronic conductivity and ion diffusion performance can be obtained, thus solving the problems existing in the traditional two-dimensional MX2 electrode materials in the application of sodium-ion batteries, such as volume change, poor conductivity, and slow ion diffusion during the battery cycle.
[0068] The advantage of this embodiment is that the intrinsic phase structure of two-dimensional MX2 is changed through phase engineering design, and a metal conductive phase with an increased interlayer spacing and beneficial to electron migration and ion diffusion is obtained. Thereby, the problems existing in the two-dimensional MX2 electrode materials in the application of sodium-ion batteries, such as volume change, poor conductivity, and slow ion diffusion during the battery cycle, are solved, and its sodium storage performance is improved. In addition, by optimizing the preparation process, a target product with a higher content can be obtained, which is suitable for fast charging applications of sodium-ion batteries with a wide temperature range.
[0069] Specifically, the 1T-phase two-dimensional transition metal chalcogenide nanosheet and its composite material 1T two-dimensional transition metal chalcogenide nanosheet / graphene have achieved fast charging performance for sodium-ion batteries with a wide temperature range. Similarly, using this phase engineering strategy, other 1T MX2 and composite 1T MX2 can be obtained and their fast charging for sodium-ion batteries with a wide temperature range can be realized.
[0070] The present invention will be further described below in conjunction with specific embodiments.
[0071] Example 1
[0072] A preparation method of 1T-phase ReSe2 includes the following steps:
[0073] (1) Weigh stoichiometric amounts of rhenium powder and selenium powder as the rhenium source and selenium source respectively. Among them, the rhenium powder and selenium powder are weighed in a molar ratio of 1:2, and a total of 1 g of raw materials are thoroughly ground in a mortar to make them evenly mixed. Under a vacuum condition of 5.5×10 -4 Pa, the evenly mixed raw materials are sealed in a quartz tube. The quartz tube with the raw materials is heated in a muffle furnace at a heating rate of 1 °C per minute to 900 °C and kept warm for 72 hours. Subsequently, the sample is cooled to room temperature with the furnace, and 1T'ReSe2 can be obtained.
[0074] As Figure 2 shown, the peak positions and relative intensities of the X-ray diffraction peaks indicate that the prepared sample is 1T'-phase ReSe2.
[0075] As Figure 3 shown in a of, the 1T'-phase ReSe2 has a layered structure; as Figure 3As shown in Figure b, the 1T'-phase ReSe2 sample exhibits a rhombic chain-like atomic arrangement with a lattice spacing of 0.245 nm, corresponding to the (2 - 21) plane.
[0076] (2) Add the 1T'-phase ReSe2 to a mixed solution of water and ethanol, ultrasonicate at room temperature for 4 hours with an ultrasonic power of 900 W, centrifuge at low speed, and pipette the supernatant to obtain well-exfoliated 1T'-phase ReSe2 nanosheets.
[0077] (3) Weigh 0.2 g of 1T'-phase ReSe2 nanosheets in a glove box filled with argon. Weigh metallic lithium such that the molar ratio of 1T'-phase ReSe2 nanosheets to metallic lithium is 1:5. Mix them and load into a quartz tube. Wash the quartz tube containing the raw materials several times with ammonia gas to remove air and impurities, then immerse it in a liquid nitrogen bath. The ammonia gas in the quartz tube condenses into liquid ammonia. When the raw material powder in the quartz tube is immersed in the liquid ammonia bath, the lithiation reaction immediately starts, marked by the liquid color gradually changing from blue to light blue and then to colorless. When the lithiation reaction stops, take out the quartz tube with heat-insulating gloves and place it in a safe place waiting for the liquid ammonia to vaporize. Wash the powder in the quartz tube with a mixed solution of water and ethanol, centrifuge at low speed and take the supernatant to obtain 1T-phase ReSe2 nanosheets with a symmetric phase structure and a triangular lattice arrangement morphology.
[0078] According to Figure 4 the X-ray diffraction patterns and Raman spectra of the 1T'-phase ReSe2 nanosheets ( Figure 4 Figure a) and 1T-phase ReSe2 nanosheets ( Figure 4 Figure b), it can be seen that the intensity of the (010) peak of the lithiated 1T'-ReSe2 nanosheets gradually weakens, indicating an improvement in structural symmetry and the formation of the 1T phase. Due to the low crystal symmetry, the 1T'-ReSe2 nanosheets exhibit a complex Raman spectrum ( Figure 4 Figure b), with peaks at 106.66, 117.95, 124.16, and 138.71 cm -1 , corresponding to in-plane vibration modes (Eg), and peaks at 159.48 and 172.53 cm -1 , corresponding to out-of-plane vibration modes (Ag). In the 1T ReSe2 nanosheets, the Raman peaks at 117.95, 124.16, 159.48, and 172.53 cm -1 show a red shift, which is due to the stretching of the lattice along the Re chain direction and the improvement of crystal structure symmetry.
[0079] Observe the 1T'-phase ReSe2 nanosheets and 1T-phase ReSe2 nanosheets using electron microscopes with different magnifications to obtain Figure 5 and Figure 6 , as shown in Figure 5In a), ultrasonic direct exfoliation of bulk 1T'-phase ReSe2 yields nanosheets of 1T'-phase ReSe2. Similarly, lithiated 1T'-phase ReSe2 nanosheets still maintain the nanosheet morphology ( Figure 5 as shown in b). Figure 6 From the high-resolution TEM (HRTEM) image and the related fast Fourier transform (FFT) pattern in a), it can be seen that the Re atoms in the 1T'-phase ReSe2 NSs are arranged in a rhombic pattern, forming a distorted octahedral structure, while the 1T-phase ReSe2 NSs exhibit a triangular lattice arrangement ( Figure 6 as shown in b), which is in good agreement with the results of X-ray diffraction, indicating that a structural transformation from the 1T'-phase to the 1T-phase occurs in the ReSe2 nanosheets during the lithiation process.
[0080] The Re atoms in the 1T'-phase ReSe2 nanosheets are arranged in a rhombic pattern, forming a distorted octahedral structure, which is a semiconductor, resulting in low electronic conductivity of the 1T'-phase ReSe2 nanosheets; while the 1T-phase ReSe2 nanosheets exhibit a triangular lattice arrangement, which is metallic, enhancing the conductivity of ReSe2, and the 1T-phase ReSe2 has longer Re-Se bonds, which is beneficial to the structural stability of the sodiation and desodiation processes.
[0081] There are the following obvious differences in the structures and properties among 1T'-phase ReSe2, 2H-phase ReSe2, and 1T-phase ReSe2:
[0082] 1. Structural differences
[0083] 1T-phase: It has an octahedral coordination structure, and each Re atom is surrounded by six Se atoms, forming a symmetric octahedron.
[0084] 1T'-phase: It is a distorted version of the 1T-phase. The Re atoms are displaced, resulting in octahedral distortion, reduced symmetry, and the formation of dimers or chain-like structures.
[0085] 2H-phase: The metal atoms are in a trigonal prism coordination environment, and each metal atom is surrounded by 6 S(Se) atoms, forming an S(Se)-M-S(Se) sandwich structure.
[0086] 2. Electronic properties
[0087] 1T-phase: It usually exhibits metallicity or a narrow bandgap semiconductor.
[0088] 1T'-phase: Due to structural distortion, it may exhibit different electronic properties, such as a larger bandgap or topological insulator characteristics.
[0089] 2H-phase: The trigonal prism coordination of the 2H-phase leads to d-orbital splitting (such as the dominance of the d2 2 orbital occupancy), forming a semiconductor energy band.
[0090] 3. Stability
[0091] 1T phase: A thermodynamically metastable phase that is relatively stable under specific conditions.
[0092] 1T' phase or 2H phase: Thermodynamically stable phases.
[0093] 4. Applications
[0094] 1T phase: Suitable for applications that require metallicity or narrow-bandgap semiconductors.
[0095] 1T' phase or 2H phase: Suitable for applications that require topological insulators or specific electronic properties.
[0096] The 1T' phase ReSe2 nanosheets and 1T phase ReSe2 nanosheets are used for energy storage in a wide temperature range of sodium-ion batteries, and the specific capacity is tested at different temperatures. As Figure 7 , Figure 8 and Figure 9 shown, it shows that the 1T phase ReSe2 nanosheets have more excellent fast charging performance in a wide temperature range for sodium-ion batteries compared with the 1T' phase ReSe2 nanosheets (maintaining a capacity of 197 mAh g -1 @20Ag -1 after 8000 cycles at room temperature, and still maintaining a capacity of 136 mAh g -1 @1Ag -1 and a capacity retention rate of 60% after 465 cycles at low temperature of -40 °C).
[0097] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.
Claims
1. A preparation method of two-dimensional transition metal chalcogenide nanosheets, characterized in that, It includes the following steps: S1: Take the transition metal elemental powder and chalcogen elemental powder, mix them evenly, heat up to 700 to 1100 °C and keep warm for more than 72 hours, then cool to room temperature to obtain 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide; S2: Add the 1T'-phase two-dimensional transition metal chalcogenide into the mixed solution formed by water and ethanol, ultrasonicate for 2 to 4 hours, centrifuge and take the supernatant to obtain the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets; S3: Under the environment of inert gas, mix the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets with metallic lithium to carry out a lithiation reaction, add them into the mixed solution formed by water and ethanol for cleaning, centrifuge and take the supernatant to obtain 1T-phase two-dimensional transition metal chalcogenide nanosheets with a symmetric phase structure of 1T-phase and a triangular lattice arrangement morphology.
2. The preparation method of the two-dimensional transition metal chalcogenide nanosheets according to claim 1, wherein The step S1 includes: The transition metal elemental powder and chalcogen elemental powder with a molar ratio of 1:2 are fully ground and mixed evenly in a mortar, sealed in a quartz tube under vacuum conditions, and heated up to 700 to 1100 °C at a heating rate of 1 to 2 °C per minute for heat preservation.
3. The preparation method of the two-dimensional transition metal chalcogenide nanosheets according to claim 1, characterized in that, The power of the ultrasonication is 800 to 1000 W, and the rotation speed of the centrifugation is 300 to 4000 rpm.
4. The preparation method of the two-dimensional transition metal chalcogenide nanosheet according to claim 1, wherein The step S3 includes: Mix the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets with metallic lithium and load them into a quartz tube, introduce ammonia gas into the quartz tube, immerse it in a liquid nitrogen bath, and carry out a lithiation reaction. The sign of the reaction process is that the liquid color gradually changes from blue to light blue and then to colorless, and the lithiation reaction ends.
5. The preparation method of the two-dimensional transition metal chalcogenide nanosheet according to claim 4, wherein After the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets and metallic lithium are loaded into the quartz tube, introduce ammonia gas into the quartz tube and discharge ammonia gas multiple times to wash the inside of the quartz tube and remove the air and impurities inside the quartz tube.
6. The preparation method of the two-dimensional transition metal chalcogenide nanosheet according to claim 4, wherein, The step S3 also includes: After the lithiation reaction ends, vaporize liquid ammonia at room temperature.
7. The preparation method of the two-dimensional transition metal chalcogenide nanosheets according to claim 4, wherein, According to the method for preparing two-dimensional transition metal chalcogenide nanosheets described in claim 4, it is characterized in that the molar ratio of the exfoliated 1T'-phase or 2H-phase two-dimensional transition metal chalcogenide nanosheets to the metallic lithium is 1:
5.
8. The preparation method of the two-dimensional transition metal chalcogenide nanosheets according to claim 4, wherein, The environment of the inert gas is an argon environment or a helium environment.
9. A two-dimensional transition metal chalcogenide nanosheet, characterized in that, Prepared by using the method for preparing two-dimensional transition metal chalcogenide nanosheets described in any one of claims 1-8, the two-dimensional transition metal chalcogenide nanosheets have a symmetric phase structure of 1T-phase and a triangular lattice arrangement morphology.
10. Application of the two-dimensional transition metal chalcogenide nanosheets described in claim 9 in the field of sodium-ion battery wide-temperature-range energy storage electrode materials.