Synthesis method and use of c@siOx / moSe2@nmWCNT material based on nmWCNT

Abstract

The application discloses a kind of based on NMWCNT configuration C@SiO x / MoSe2@NMWCNT material synthesis method and purposes, and nitrogen-containing functional group is introduced on the surface of CNT as active site to form nitrogen (N) doped carbon nanotube (NMWCNT), can promote the adsorption of molybdenum selenide and silicon, and molybdenum selenide nano flap serves as the skeleton of dispersed high capacity SiO x The application forms C@SiO x / MoSe2@NMWCNT three-layer heterojunction material by ultrasonic mixing of molybdenum pentachloride, triphenyl chlorosilane, NMWCNT and ethylene glycol, and then calcining with selenium.The method of the application is simple and easy to operate, and has low cost.The SIB electrode material prepared by the method has good performance, can reach an initial specific discharge capacity of 1568mA h g ‑1 at a current density of 0.1A g ‑1 , has a specific discharge capacity of 415mA h g ‑1 after 1000 cycles at a high current density of 5A g ‑1 , and has a specific discharge capacity of 353mA h g ‑1 after 3000 cycles, has good cycle stability and high specific capacity, and is conducive to realizing large-scale production.

Description

Technical Field

[0001] This invention relates to a method for synthesizing a sodium-ion battery anode material, which is a C@SiO structure based on NMWCNT (nitrogen-doped multi-walled carbon nanotubes). x The synthesis method of / MoSe2@NMWCNT material is a research area related to sodium-ion battery anode materials. Background Technology

[0002] Currently, lithium-ion batteries (LIBs) are widely used in portable electronics and electric vehicles due to their superior energy density. However, because lithium resources are relatively scarce in the Earth's crust, it is necessary to find alternatives to lithium-ion batteries. Sodium-ion batteries (NIBs) are gaining increasing attention due to their abundant availability and similar mechanism to lithium-ion batteries. This is because sodium ions have a relatively small ionic radius (approximately...). ) compared to lithium ions (approximately Because sodium ions have a larger diameter, their insertion and extraction kinetics are slower than those of lithium ions, making it imperative to find suitable anode materials for sodium-ion batteries.

[0003] Recent studies have shown that carbon nanotubes (CNTs) with unique properties such as large specific surface area, flexibility, high chemical stability, and high conductivity are optimal templates for growing various two-dimensional materials, including TMDs. The highly porous nature of the CNT framework not only allows for extensive infiltration of electrolytes to improve electronic and ionic conductivity but also accommodates volume changes in composite materials. Furthermore, introducing nitrogen-containing functional groups as active sites on the CNT surface to form nitrogen (N)-doped carbon nanotubes (NMWCNTs) can promote the adsorption of molybdenum selenide and silicon. Two main functions of N dopants have been widely accepted: (1) N can induce a relative positive charge between adjacent C atoms, promoting the adsorption of reactants such as O2 and OH-; (2) due to the high affinity of N doping for transition metal materials, stronger coupling between N-doped carbon and metal oxides is achieved, which can greatly promote electron transfer. However, maintaining high connectivity between the nanotubes and thus improving charge storage performance requires well-controlled nitrogen-containing (N) functional groups (such as pyridine-N, pyrrole-N, graphite-N, and pyridine-oxide-N) without disrupting the nanotube structure (subsequent XPS tests also confirmed the presence of pyridine-N, pyrrole-N, and graphite-N functional groups). Furthermore, NMWCNT materials are commercially available and relatively inexpensive.

[0004] Two-dimensional (2D) layered materials, especially transition metal didops (TMDs), have attracted widespread attention for their application in energy conversion and storage devices due to their superior physical, chemical, and electronic properties. Notably, many molybdenum alloys or compounds, such as MoS2 and MoO3, possess naturally occurring two-dimensional structures, providing naturally constructed diffusion channels for metal ions, thus holding significant potential for energy storage applications. Compared to MoS2 or MoO3, MoSe2 exhibits a larger interlayer spacing and a narrower band gap, making it suitable for metal ion storage. However, due to its higher molecular weight, MoSe2 still faces challenges related to relatively low capacity and poor cycling performance.

[0005] Silicon is one of the most abundant elements on Earth and has a very high theoretical capacity (~4200 mAh g). –1 Silicon boasts a conductivity ten times higher than traditional carbon anodes. Coupled with its environmentally friendly, abundant, and low-cost characteristics, silicon has been considered one of the most promising anode materials for next-generation lithium-ion batteries (LIBs). However, silicon experiences a volume expansion of up to 400% during full lithium insertion (lithiation) and significant shrinkage during lithium extraction (delithiation), resulting in substantial capacity loss. Therefore, from a practical application perspective, the cycle performance of silicon anodes remains far from satisfactory. To overcome the problems posed by silicon, numerous strategies have been proposed, including miniaturizing silicon materials to the nanoscale, such as nanoparticles, nanowires, double-walled SiOx / Si nanotubes, nanosheets, and mesoporous silicon sponges. These nanostructures provide greater space, mitigating the large volume changes during charging and discharging and preventing electrode pulverization during lithium insertion and extraction, all showing significantly improved performance. However, in practical applications, it remains unsatisfactory as a material urgently needed for electric vehicles. This is likely due to the lack of favorable electronic conductivity and the continuous growth of the unstable solid electrolyte interface (SEI) at the Si / electrolyte interface during cycling. Therefore, there is a high demand for new designs of silicon anode structures to achieve longer cycle life and higher rate capability. Summary of the Invention

[0006] The purpose of this invention is to find a suitable negative electrode material for sodium-ion batteries, and the proposed C@SiO based on NMWCNT structure is presented here. x Synthesis method of / MoSe2@NMWCNT material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A C@SiO2 structure based on NMWCNT x The synthesis method of / MoSe2@NMWCNT material includes the following steps:

[0009] S1: Dissolve molybdenum pentachloride in a first ethylene glycol solution to form a molybdenum-based organometallic complex. Add triphenylchlorosilane and a second ethylene glycol solution to the molybdenum-based organometallic complex to form a molybdenum-based silicon organometallic complex.

[0010] S2: Add NMWCNT to the molybdenum-based silicon metal-organic complex and sonicate to disperse NMWCNT evenly, while simultaneously allowing the molybdenum-based silicon metal-organic complex to be uniformly adsorbed on the surface of NMWCNT, thus obtaining a dispersed solution;

[0011] S3: The dispersed solution was calcined under an inert gas atmosphere to generate C@SiO based on the NMWCNT structure. x / MoSe2@NMWCNT material, where 1≤X≤2.

[0012] In a further improvement, in step S1, the mass-to-volume ratio of molybdenum pentachloride to the first ethylene glycol solution is 27.2:5.6 mg / ml, and the mass ratio of molybdenum pentachloride to triphenylchlorosilane is 27.2:29.4-147.

[0013] In a further improvement, in step S1, the volume ratio of the first ethylene glycol solution to the second ethylene glycol solution is 5.6:17.

[0014] In a further improvement, in step S2, the mass ratio of NMWCNT to triphenylchlorosilane is 8:29.4-147.

[0015] As a further improvement, in step S3, the heating rate during calcination is 5℃ / min.

[0016] A further improvement is made in step S3, where the calcination method is as follows: heating at 80°C for 4 hours, heating at 180°C for 3 hours, and heating at 800°C for 4 hours.

[0017] As a further improvement, in step S2, ultrasound is performed for 4 hours.

[0018] A C@SiO2 structure based on NMWCNT x Applications of / MoSe2@NMWCNT materials, specifically the NMWCNT-based C@SiO2 structure x The synthesis method of / MoSe2@NMWCNT material is as described above, and the C@SiO material based on NMWCNT construction x / MoSe2@NMWCNT material is used as a raw material for preparing electrode materials.

[0019] A further improvement is made to the electrode material preparation method as follows:

[0020] Constructing C@SiO based on NMWCNT xThe / MoSe2@NMWCNT material is mixed with acetylene black and carboxymethyl cellulose in a mass ratio of 4:1:1 and ground. Water and ethanol are used as solvents to stir and form a slurry. The slurry is then uniformly coated onto copper foil to obtain the electrode material.

[0021] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0022] This invention uses molybdenum pentachloride, triphenylchlorosilane, selenium, NMWCNT, and ethylene glycol as raw materials, and obtains C@SiO through ultrasonic treatment and calcination. x / MoSe2@NMWCNT trilayer heterojunction composite material. This trilayer material has a stable structure, good cycling stability, and excellent electrochemical performance at 5Ag. -1 After 1000 cycles at high current density, it still has 415mAh g. -1 The discharge specific capacity, after 3000 cycles, still has 353mAh g. -1 The discharge specific capacity. Compared with existing technologies, this method is simple, uses readily available raw materials, and has a lower cost, which is conducive to its large-scale production.

[0023] This invention successfully prepares C@SiO by mixing a molybdenum-based metal compound and organosilicon to form a mixed solution, followed by ultrasonic and calcination processes. x / MoSe2@NMWCNT composite material ( Figure 1 The obtained C@SiO₂ can be confirmed by XRD. x / MoSe2@NMWCNT products. When used as the negative electrode material for SIB, at 0.1Ag -1 At a current density of 1568 mAh g, it can reach 1568 mAh g. -1 The initial discharge specific capacity at 5A g -1 After 1000 cycles at high current density, it still has 415mAh g. -1 The discharge specific capacity, after 3000 cycles, still has 353mAh g. -1 The composite material exhibits excellent discharge specific capacity, good cycle stability, and high specific capacity. The superior performance can be attributed to the following factors: First, the high theoretical capacity of silicon. The addition of silicon to the composite system, with its two-dimensional (2D) MoSe2 nanolobes acting as a dispersion agent, improves the discharge specific capacity and rate performance. Second, the formation of a three-dimensional heterojunction material, with NMWCNTs and externally coated carbon as SiO2. x / MoSe2 provides a specific space that mitigates the volume expansion caused by sodium ion extraction and insertion, increasing the cycling stability of the composite material during charge and discharge. This invention paves the way for the fabrication of C@SiO. xThe / MoSe2@NMWCNT composite material provides a simple synthesis method and lays the foundation for the development of future high-performance anode materials. Attached Figure Description

[0024] Figure 1 C@SiO x The preparation process of / MoSe2@NMWCNT is shown in the figure, in which (a) triphenylchlorosilane, MoCl5 and ethylene glycol are mixed to form a molybdenum-based silicon organometallic complex, which is then compounded with NMWCNT by ultrasonic treatment. (b) The above solution is calcined and selenized in situ to synthesize C@SiO. x The / MoSe2@NMWCNT three-layer heterojunction material also shows SiO2 in TEM images. x / MoSe2 adheres to NMWCNTs and forms a carbon coating layer.

[0025] Figure 2 The images show the microstructure and elemental distribution of C@MoSe2, where (a) is the SEM image of C@MoSe2, (b) is the 20nm TEM image of C@MoSe2, (c) is the 2nm TEM image of C@MoSe2, (d) is the elemental distribution electron image of C@MoSe2@NMWCNT, and (e), (f) and (g) are the EDS-mapping elemental distribution images of C, Mo and Se, respectively.

[0026] Figure 3 C@SiO x SEM images of @NMWCNT, where (a), (b), (d), and (e) are SEM images of different locations at a 200nm size, and (c) and (f) are SEM images of different locations at a 100nm size.

[0027] Figure 4 C@SiO x TEM image of @NMWCNT. (a) shows C@SiO. x TEM image of @NMWCNT, (b) is C@SiO x STEM images of @NMWCNT, (c) is the elemental distribution map of C@MoSe2@NMWCNT, and (d), (e), (f) and (g) are the EDS-mapping elemental distribution maps of C, N, O and Si, respectively.

[0028] Figure 5 C@SiO x SEM images of / MoSe2@C, where (a)-(f) are SEM images at sizes of 2μm, 1μm, 500nm, 2μm, 1μm and 500nm, respectively.

[0029] Figure 6 C@SiO x TEM images of / MoSe2@C. (a)-(c) are C@SiO2, respectively. x TEM images of / MoSe2@C at 500nm, 100nm, and 200nm, (d)C@SiO x The elemental distribution diagram of / MoSe2@C is shown. (e), (f), (g), (i), and (h) are the EDS-mapping elemental distribution diagrams of C, O, Si, Se, and Mo, respectively.

[0030] Figure 7 Here are SEM images of the products, where (a)-(c) are C@SiO x SEM images of / MoSe2-2-1@NMWCNT at 2μm, 1μm, and 500nm respectively; (d)-(f) are C@SiO x / MoSe2-3-1@NMWCNT(d)-(f) SEM images at 2μm, 1μm and 500nm; (g)-(i) C@SiO x / MoSe2-4-1@NMWCNT(g)-(i) SEM images at 2μm, 1μm and 500nm; (j)-(l) are C@SiO x SEM images of / MoSe2-5-1@NMWCNT at 2μm, 1μm, and 500nm.

[0031] Figure 8 C@SiO x TEM images of / MoSe2-3-1@NMWCNT. (a)-(b) C@SiO x TEM images of / MoSe2-3-1@NMWCNT at 200nm, 50nm, 10nm, and 10nm, (cd)C@SiO x HRTEM plot of / MoSe2-3-1@NMWCNT, (e)C@SiO x STEM image of / MoSe2-3-1@NMWCNT, (f) shows C@SiO x The elemental distribution diagram of / MoSe2-3-1@NMWCNT, (g), (h), (i), (j), (k) and (l) are the EDS-mapping elemental distribution diagrams of C, N, O, Si, Se and Mo, respectively.

[0032] Figure 9 For comparison of products at each stage Figure 1 Among them, (a) is C@MoSe2 and C@SiO x / MoSe2@C and C@SiO xXRD patterns of / MoSe2@NMWCNT; (b) and (c) are C@MoSe2, NMWCNT, and C@SiO, respectively. x / MoSe2@C and C@SiO x Raman characterization of / MoSe2@NMWCNT and C@SiO x XPS fine spectral analysis of / MoSe2@NMWCNT; (d) Mo 3d plot; (e) Se 3d plot; (f) Si 2p plot.

[0033] Figure 10 For comparison of products at each stage Figure 2 Wherein, (a) is C@MoSe2, NMWCNT, C@SiO x / MoSe2@C and C@SiO x Raman characterization of / MoSe2@NMWCNT, (b) is C@SiO x Full spectrum analysis and fine spectrum analysis plots of XPS for / MoSe2@NMWCNT; (c) is the C1s plot; (d) is the N1s plot.

[0034] Figure 11 For thermogravimetric analysis of C@MoSe2, C@MoSe2@NMWCNT, and C@SiO x / MoSe2(2-1)@NMWCNT、C@SiO x / MoSe2(3-1)@NMWCNT and C@SiO x Figure showing the MoSe2 content in the / MoSe2(4-1)@NMWCNT composite system.

[0035] Figure 12 For C@MoSe2, C@MoSe2@NMWCNT, C@SiO x SEM images of the product obtained after calcining / MoSe2(3-1)@NMWCNT(gi) at 900℃ (Air) for 4 h are shown. (a)-(c) are related images of C@MoSe2(ac), (d)-(f) are related images of C@MoSe2@NMWCNT, and (g)-(i) are related images of C@SiO2. x Related images of / MoSe2(3-1)@NMWCNT.

[0036] Figure 13The images show TEM images of the product obtained after calcining C@MoSe2 at 900℃ (Air) for 4 h. (a)-(b) are 2 μm TEM images of C@MoSe2-900Air, (c) is a STEM image of C@MoSe2-900Air, (d) is the elemental distribution of C@MoSe2-900Air, and (f), (g) and (h) are EDS-mapping elemental distribution maps of C, O and Mo, respectively.

[0037] Figure 14 .for C@SiO x TEM images of the product obtained after calcining / MoSe2(3-1)@NMWCNT(gi) at 900℃ (Air) for 4 h were obtained, where (a) represents C@SiO2. x STEM image of / MoSe2(3-1)@NMWCNT-900Air, (b) is C@SiO x The elemental distribution diagram of / MoSe2(3-1)@NMWCNT-900Air is shown in (c), (d), (f), (g) and (h), which are the EDS-mapping elemental distribution diagrams of C, N, O, Si and Mo, respectively, and (e) is the atomic percentage diagram.

[0038] Figure 15 For the composite material C@SiO x Sodium storage performance of / MoSe2@NMWCNT. (a) shows the sodium storage performance of the composite material C@SiO. x (a) CV curve of / MoSe2(3-1)@NMWCNT; (b) C@SiO composite material x / MoSe2(3-1)@NMWCNT of 100mAg -1 Charge-discharge curves; (c) shows the C@SiO composite material. x / MoSe2(1-1)@NMWCNT、C@SiO x / MoSe2(2-1)@NMWCNT、C@SiO x / MoSe2(3-1)@NMWCNT、C@SiO x / MoSe2(4-1)@NMWCNT and C@SiO x / MoSe2(5-1)@NMWCNT at 0.5Ag -1 Cyclic performance diagram under current; (d) shows the composite material C@SiO x Rate performance diagram of / MoSe2(3-1)@NMWCNT; (e) shows the composite material C@SiO x / MoSe2(3-1)@NMWCNT under high current 5Ag -1 The long-cycle stability plot below.

[0039] Figure 16 For the composite material C@MoSe2 at 0.1A g -1 Cyclic performance under current and composite material C@SiO x / MoSe2@C、C@SiO x @NMWCNT at 0.5Ag -1 Cyclic performance diagram under current.

[0040] Figure 17 The in-situ SEM analysis results for C@SiOx / MoSe2(3-1)@NMWCNT are shown in the diagrams. (a) shows the charging process from an open-circuit voltage (OCV) of 0.001V to 3.0V, and (b) shows the changes after discharging from an OCV of 3.0V to 0.001V. Detailed Implementation

[0041] To make the above-described features, advantages, and objectives of the present invention more apparent, the present invention will be further described in detail below with reference to specific embodiments. Many specific details have been set forth in the above description to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0042] Unless otherwise specified, the reaction raw materials and catalysts involved in the following examples are all commercially available reagents.

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0044] Example 1

[0045] The construction of C@MoSe2 heterojunction composite materials and their sodium storage properties were studied. The preparation method of this composite material includes the following steps:

[0046] S1. Mix ethylene glycol (15 mL) and MoCl5 (27.2 mg) together to form a mixed solution;

[0047] S2. Sonicate the above solution for 4 hours to ensure uniform dispersion of the molybdenum-based metal-organic complex;

[0048] S3. Then pour this mixed solution into a ceramic boat containing Se (24 mg), place it in a tube furnace and calcine it to 800 °C under an argon atmosphere at a heating rate of 5 °C / min.

[0049] S4. After ultrasonication and calcination, the Mo element in the precursor dispersion is selenized in situ to MoSe2, while the organic components are converted into carbon materials in situ, ultimately generating C@MoSe2 nanocomposite heterojunction materials.

[0050] In S1, the temperature during the addition process is room temperature.

[0051] In S4, the product is a C@MoSe2 composite material, that is, a carbon coating layer is formed on the surface of MoSe2.

[0052] The obtained C@MoSe2 nanocomposite heterojunction material was mixed and ground with acetylene black and carboxymethyl cellulose (CMC) in a mass ratio of 4:1:1. Water and ethanol were used as solvents to stir and form a slurry, which was then uniformly coated on copper foil to serve as an electrode material.

[0053] Example 2

[0054] Constructing C@SiO x The synthesis method of @NMWCNT heterojunction composite material includes the following steps:

[0055] S1. Mix ethylene glycol (15 mL) and triphenylchlorosilane (88.2 mg) together to form a mixed solution, and finally dissolve NMWCNT (8 mg) in the aforementioned solution;

[0056] S2. Sonicate the above solution for 4 hours to uniformly disperse the silicon and allow it to adsorb onto the surface of NMWCNT.

[0057] S3. Then pour this mixture into a ceramic boat and place it in a tube furnace to calcine to 800°C under an argon atmosphere at a heating rate of 5°C / min.

[0058] S4. After ultrasonication and calcination, the organosilicon in the precursor dispersion is oxidized to silicon oxide, while the organic components are converted in situ into carbon materials, ultimately generating C@SiO. x @NMWCNT nanocomposite heterojunction material.

[0059] In S1, the temperature during the addition process is room temperature;

[0060] The product is C@SiO x @NMWCNT nano-trilayer composite heterojunction material, namely SiO x Uniform adsorption onto NMWCNTs, while a carbon coating layer is formed on the surface, forming a carbon-coated three-layer composite heterojunction material C@SiO. x @NMWCNT.

[0061] The obtained C@SiO x@NMWCNT nano-trilayer composite heterojunction material is mixed and ground with acetylene black and carboxymethyl cellulose (CMC) in a mass ratio of 4:1:1. Water and ethanol are used as solvents to stir and form a slurry, which is then uniformly coated on copper foil to serve as an electrode material.

[0062] Example 3

[0063] Constructing C@SiO x A method for synthesizing / MoSe2@C heterojunction composite materials, the preparation method of which includes the following steps:

[0064] S1. Dissolve molybdenum pentachloride (27.2 mg) in ethylene glycol (5.6 mL) to form a molybdenum-based organometallic complex, and then add triphenylchlorosilane (88.2 mg) and ethylene glycol (17 mL);

[0065] S2. Sonicate the above solution for 4 hours to uniformly disperse the molybdenum-based organometallic complex and silicon.

[0066] S3. Then pour this mixed solution into a ceramic boat containing Se (24 mg), place it in a tube furnace and calcine it to 800 °C under an argon atmosphere at a heating rate of 5 °C / min.

[0067] S4. After ultrasonication and calcination, the Mo element in the precursor dispersion is selenized in situ to MoSe2, the organosilicon is oxidized to silicon oxide, and the organic components are converted in situ into carbon materials, ultimately generating C@SiO. x / MoSe2@C nanocomposite heterojunction material.

[0068] In S1, the temperature during the addition process is room temperature;

[0069] In S4, the product is C@SiO x / MoSe2@C nanolayer composite heterojunction material, namely SiO x The carbon coating is uniformly dispersed on MoSe2 nanosheets, and a carbon coating layer is formed on the surface of MoSe2, forming a three-layer composite heterojunction material C@SiO with a double carbon coating. x / MoSe2@C.

[0070] The obtained C@SiO x / MoSe2@C nano-trilayer composite heterojunction material is mixed and ground with acetylene black and carboxymethyl cellulose (CMC) in a mass ratio of 4:1:1. Water and ethanol are used as solvents to stir and form a slurry, which is then uniformly coated on copper foil to serve as an electrode material.

[0071] Example 4

[0072] A C@SiO2 structure based on NMWCNT xA method for synthesizing / MoSe2@NMWCNT materials, the preparation method of which includes the following steps:

[0073] S1. First, dissolve molybdenum pentachloride (27.2 mg) in a certain amount of ethylene glycol to form a molybdenum-based organometallic complex. Then, add triphenylchlorosilane (29.4 mg, 58.8 mg, 88.2 mg, 117.6 mg, 147 mg) and a certain amount of ethylene glycol in different proportions. Finally, dissolve NMWCNT (8 mg) in the above solution. The best effect is achieved by adding 5.6 mL of ethylene glycol in the first addition and 17 mL of ethylene glycol in the second addition. The optimal molar ratio of triphenylchlorosilane to molybdenum pentachloride is 3:1.

[0074] S2. Sonicate the solution for 4 hours to uniformly disperse the molybdenum-based metal-organic complex and silicon, and at the same time uniformly adsorb onto the surface of NMWCNT.

[0075] S3. Then pour this mixed solution into a ceramic boat containing Se (24 mg), place it in a tube furnace and calcine it to 800 °C under an argon atmosphere (heat at 80 °C for 4 h, at 180 °C for 3 h, and at 800 °C for 4 h), with a heating rate of 5 °C / min.

[0076] S4. After ultrasonication and calcination, the Mo element in the precursor dispersion is selenized in situ to MoSe2, the organosilicon is oxidized to silicon oxide, and the organic components are converted in situ into carbon materials, ultimately generating C@SiO. x / MoSe2@NMWCNT nanocomposite heterojunction material.

[0077] In S1, the temperature during the addition process is room temperature;

[0078] In S4, the product is C@SiO x / MoSe2@NMWCNT nanotrilayer composite heterojunction material, namely SiO x The carbon nanosheets were uniformly dispersed on MoSe2 nanosheets and then adsorbed onto NMWCNTs. Simultaneously, a carbon coating layer was formed on the MoSe2 surface, resulting in a three-layer composite heterojunction material C@SiO. x / MoSe2@NMWCNT;

[0079] The obtained C@SiO x / MoSe2@NMWCNT nano-trilayer composite heterojunction material is mixed and ground with acetylene black and carboxymethyl cellulose (CMC) in a mass ratio of 4:1:1. Water and ethanol are used as solvents to stir and form a slurry, which is then uniformly coated on copper foil to serve as an electrode material.

[0080] The following uses Examples 1-4 as representatives for characterization:

[0081] Using SEM and TEM techniques to study C@MoSe2 and C@SiO x @NMWCNT、C@SiO x / MoSe2@C、C@SiO x The structure of / MoSe2@NMWCNT was characterized. Figure 2 a indicates that C@MoSe2 has a sheet-like structure, which interweaves to form a 3D flower-like structure. Furthermore, Figure 2 TEM and HRTEM images b and c confirmed the presence of a carbon coating layer on the MoSe2 structure. It was also observed that the large nanosheets were composed of interwoven individual small MoSe2 nanosheets. Furthermore, while the MoSe2 nanosheets were surrounded by carbon layers, the number of MoSe2 layers was relatively small (around 10 layers). Figure 2 d HAADF-STEM images and Figure 2 The corresponding elemental diagram in e–g shows the uniform distribution of Mo, Se, and C elements in the nanosheet structure, further confirming that a carbon layer covers the MoSe2 nanosheets. The formation of few-layer MoSe2 nanosheets is mainly due to the dispersing effect of EG on the Mo-based organometallic complex, and the organic components in the Mo-based organometallic complex can act as a carbon source for the formation of the carbon layer. Figure 3 and 4 All indicate that carbon-coated SiO x A three-layer heterojunction composite material C@SiO is formed on NMWCNT. x @NMWCNT, and C@SiO x The adsorption has almost no effect on the morphology of NMWCNTs. Figure 4 The EDS elemental analysis of dg showed the presence of four elements: C, Si, O, and N. The clusters of Si and O elements also confirmed the presence of SiO. x The formation of this also prepares the site for the subsequent addition of MoSe2, which acts as a disperser for SiO2. x The framework provided ideas. Figure 5 and 6 C@SiO x / MoSe2@C formed a large number of MoSe2 nanosheets, according to Figure 6 TEM electron images and EDS elemental analysis of ci show that SiO x The formation of MoSe2 and the uniform distribution of Mo, Se, C, O, and Si elements also indicate that SiO2... x The carbon components are uniformly dispersed on MoSe2 nanosheets, and the organic components act as a carbon source to form a carbon coating layer. Figure 7 It is C@SiO x SEM image of / MoSe2@NMWCNT, where SiO x / MoSe2=2:1(ac),SiO x / MoSe2=3:1(df), SiO x / MoSe2=4:1(gi),SiO x With a SiO2 ratio of 5:1 (jl), comparing the four sets of figures above, it can be observed that the morphology of NMWCNTs changes slightly with the increase of the SiO2 ratio. Figures (gi) and (jl) show that the NMWCNT surface is somewhat deformed and coated with a thick layer. This morphology is unfavorable for sodium ion transport, reducing sodium ion mobility. Compared to figures (gi) and (jl), the carbon nanotube framework in figures (ac) and (df) is almost unaffected. Especially in figure (df), the MoSe2 nanosheets on the NMWCNTs are clearly visible; some grow on the NMWCNTs like fish scales, while others emerge like leaves. These MoSe2 nanosheets increase the contact area with the electrolyte and provide better channels for sodium ion entry, improving sodium ion mobility and the utilization rate of the active material. C@SiO2 x The HAADF-STEM images of / MoSe2@NMWCNT also show that leaf-like MoSe2 nanosheets grow at an angle on NMWCNTs. Figure 8 b, Figure 8 EDS elemental analysis of (el) showed that the six elements C, N, O, Mo, Se, and Si were evenly distributed, which also indicates that SiO x The uniform dispersion on MoSe2 nanosheets provides the composite material with high capacity during charge and discharge. Figure 8 (cd) HRTEM images also show that MoSe2 nanosheets were successfully grown on NMWCNTs, and the surface was successfully coated with a carbon layer. This is beneficial for improving the stability of the composite material during charge and discharge processes.

[0082] HR-TEM Figure 2 c. Figure 8 c and Figure 8 The interlayer spacing of d is approximately 0.65 nm, corresponding to the (002) plane of MoSe2, which also proves that a large number of molybdenum selenide nanosheets are formed. The formation of molybdenum selenide nanosheets provides a good channel for sodium ion insertion, increases the sodium ion storage capacity, and also plays a role in dispersing and storing silicon, thereby improving the performance of the battery.

[0083] The materials were then subjected to XRD, Raman, and XPS analyses to further verify the properties of the synthesized materials. Figure 9 a demonstrates C@MoSe2, C@SiO x / MoSe2@C and C@SiOx XRD images of / MoSe2@NMWCNT from 10-80 (2θ). C@SiO x / MoSe2@C and C@SiO x The peak at 26.2° of / MoSe2@NMWCNT corresponds to the (011) plane of SiO2 (JCPDS PDF#47-1144), and the peaks at 47° and 56° correspond to SiO (JCPDS PDF#30-1127). Apart from these peaks, all other peaks correspond to the MoSe2 (JCPDS PDF#29-0914) peak group, indicating that MoSe2 was mainly formed. Figure 9 b and 9c demonstrate C@MoSe2, NMWCNT, and C@SiO2. x / MoSe2@C and C@SiO x Raman images of / MoSe2@NMWCNT, such as Figure 9 As shown in b, 238.0cm -1 and 283.1cm -1 They are Mo-Se out-of-plane (A) 1g and in the plane The atomic vibration modes. It can be seen from A... 1g arrive The strength ratio of C@MoSe2 (12.29) and C@SiO is higher. x / MoSe2@C(1.08) and C@SiO x The significant difference between / MoSe2@NMWCNT(1.19) indicates that SiO2... x It has a certain influence on the layered structure of MoSe2, and also confirms that SiO2... x Inserted and attached to the layered structure of MoSe2, forming SiO x / MoSe2 composite material, and also explains the relationship between NMWCNT and SiO x There is a strong interaction between / MoSe2. Figure 9 c of C@MoSe2,NMWCNT,C@SiO x / MoSe2@C and C@SiO x Raman images of / MoSe2@NMWCNT show that 1352cm - 1 and 1586cm -1 The two peaks at that point represent the D and G segments of NMWCNT, with D / G intensity ratios corresponding to C@MoSe2 (0.91), NMWCNT (1.0), and C@SiO2, respectively. x / MoSe2@C(0.96), C@SiO xThe results of / MoSe2@NMWCNT(0.92) show that the strength ratios are almost identical, proving that their defect levels are similar.

[0084] Analysis of C@SiO using XPS technology x Surface chemical composition and oxidation state of elements in the / MoSe2@NMWCNT composite material. (Full spectrum) Figure 10 Signals of Mo, Se, Si, C, N, and O elements can be observed in b), with the Mo 3d spectrum showing the most significant signal. Figure 9 d), 228.8 eV and 225.7 eV are respectively Mo 3d 3 / 2 Signal and Mo 3d 5 / 2 The signal indicates that Mo 4+ The state. In the Se 3d spectrum ( Figure 9 e), 55.8 eV and 54.6 eV are Se 3d 3 / 2 and Se 3d 5 / 2 Signal, i.e., Se 2+ State. In the Si 2p spectrum ( Figure 9 f), the signals at 103.9 eV and 103 eV correspond to tetravalent silicon and divalent silicon, respectively, confirming the formation of SiO2 and SiO. In the N1s spectrum ( Figure 10 d) can be mainly divided into three peaks: 401.1 eV (Graphitic-N), 399.3 eV (Pyrrolic-N), and 395.1 eV (Pyridinic-N), representing three different types of nitrogen. In the C1s spectrum, there are four main peaks at 284.8 eV, 285.6 eV, 286.8 eV, and 288.8 eV, corresponding to C / C, CN, CO, and C=O bonds, respectively.

[0085] Thermogravimetric analysis (TGA) can be used to analyze the thermogravimetric analysis (TGA) Figure 11 To determine the MoSe2 and SiO content in C@MoSe2, C@MoSe2@NMWCNT and C@SiO / MoSe2(2 / 3 / 4-1)@NMWCNT. x The content of SiO₂. When heated in air, SiO₂... x It will completely transform into SiO2, and its weight change is negligible. MoSe2 will oxidize to MoO3 and SeO2 before 350℃, so a weight increase will occur. Afterwards, there will be two weight reduction stages. The first stage is due to the sublimation of SeO2, and the second stage is due to the oxidation of carbon. At temperatures reaching 900-1000℃, the residues of C@MoSe2 and C@MoSe2@NMWCNT are only 2.2% and 3.5%, respectively. This was verified by SEM (…). Figure 12 ) and TEM Figure 13 The products of C@MoSe2 and C@MoSe2@NMWCNT calcined at 1000℃ for 4 h were analyzed, and the results showed that the products were mainly MoO3 encapsulated in a CO-Mo framework. Figure 13 As can be seen from e, MoO3 accounts for 99.47% of the product composition, belonging to the main component). Combining the conservation of Mo element, the content of MoSe2 can be calculated by the following formula (1).

[0086]

[0087] In the formula and The molecular weights of MoSe2 and MoO3 are respectively. and These represent the masses of MoSe2 and MoO3 contained in the system (400-600℃), respectively. and C@MoSe2, C@MoSe2@NMWCNT, C@SiO / MoSe2(2-1)@NMWCNT, C@SiO / MoSe2(3-1)@NMWCNT, C@SiO / MoSe2(4-1)@NMWCNT The percentages were 53.1%, 30.4%, 30.9%, 25.2%, and 23.9%, respectively. The calculated MoSe2 contents in C@MoSe2, C@MoSe2@NMWCNT, C@SiO / MoSe2(2-1)@NMWCNT, C@SiO / MoSe2(3-1)@NMWCNT, and C@SiO / MoSe2(4-1)@NMWCNT were 93.6%, 53.6%, 54.5%, 44.4%, and 42.2%, respectively. The SiO2 content in C@SiO / MoSe2(2-1)@NMWCNT, C@SiO / MoSe2(3-1)@NMWCNT, and C@SiO / MoSe2(4-1)@NMWCNT was 53.1%, 30.4%, 30.9%, 25.2%, and 23.9%, respectively. x The contents were 2.5%, 14%, and 19.2%, respectively.

[0088] Next, we tested C@MoSe2 and C@SiO by making button cells. x @NMWCNT、C@SiO x / MoSe2@C、C@SiO x The energy storage performance of sodium-ion batteries using four materials: / MoSe2@NMWCNT. Figure 15 a showcased C@SiO xCyclic voltammetry (CV) curves of the / MoSe2@NMWCNT composite material as a SIB electrode are shown. In the first CV scan, three cathodic peaks (1.03 V, 0.63 V, and 0.36 V) appeared during discharge. The peak at 1.03 V is due to Na… + Insertion of MoSe2 to form Na x The MoSe2 process, with peak values ​​at 0.63V and 0.36V respectively for SiO2. x The irreversible transformation of Na₂Se and the formation of the solid electrolyte interphase (SEI) layer are noteworthy. These two peaks disappear during the second cycle, leading to the initial irreversible high capacity. During charging, there are two anodic peaks (1.73V and 2.0V). The peak at 1.73V corresponds to the reversible conversion of Na₂Se and metallic Mo to MoSe₂, while the peak at 2.0V is attributed to silicon extraction. From the second cycle onwards, the main discharge peak at 1.38V is due to further sodium ion insertion, causing MoSe₂ to decompose into metallic Mo and hexagonal Na₂Se. Two charging peaks remain at 1.74V and 2.1V, close to those of the first cycle. The peak at 1.74V is due to the partial oxidation of metallic Mo to MoSe₂ and the partial conversion of Na₂Se to Se, while the peak at 2.1V is due to further silicon extraction. Furthermore, from the second cycle onwards, the CV curves nearly overlap, indicating the material's stability during charge and discharge. Figure 15 b showcases the material C@SiO x Electrostatic charge-discharge curves of / MoSe2@NMWCNT as SIB electrodes (0.1A g) -1 (Below), the initial discharge capacity and charge capacity are 1178mAh g. -1 and 649mAh g -1 The initial charge / discharge efficiency was 55%. The low initial charge / discharge efficiency may be due to the formation of the SEI film during the initial charge / discharge process.

[0089] Figure 15 c shows the material C@SiO x / MoSe2@NMWCNT in SiO x Charge-discharge specific capacity and cycle stability (at 0.5 Ag) of MoSe2 at ratios of 1:1, 2:1, 3:1, 4:1, and 5:1. -1 Below, the first five cycles are at 0.1Ag -1 (See below), as can be seen from the figure, in SiO x When the ratio of MoSe2 is 1:1, 2:1, 4:1, or 5:1, the charge-discharge capacity is relatively low, especially in SiO2. xWhen the MoSe2 ratio is 3:1, a higher charge-discharge specific capacity and better cycle stability are observed, maintaining a capacity of 620 mAh g after 300 cycles. -1 The specific discharge capacity. For example... Figure 16 As shown, in the absence of SiO x Alternatively, when NMWCNTs are involved, the SIB electrode exhibits significant capacity decay and poor cycling stability at 0.1 Ag. -1 After 300 cycles, the discharge specific capacity of C@MoSe2 decreased to 99 mAhg. -1 At 0.5Ag -1 Below, C@SiO x @NMWCNT Due to the addition of silicon, the initial charge / discharge specific capacity increases, but after five cycles, the charge / discharge specific capacity begins to decrease, and the average discharge specific capacity is 225 mAh g over 300 cycles. -1 Left and right. C@SiO x / MoSe2@C at 0.5Ag -1 After 300 cycles, the discharge specific capacity decreased to 378 mAh g. -1 The cycle stability is poor. This indicates that C@SiO x The three-layer heterojunction structure formed by the / MoSe2@NMWCNT composite material exhibits high charge-discharge specific capacity and good cycle stability, among which SiO2... x and MoSe2 in a 3:1 ratio (C@SiO) x The addition of / MoSe2-3-1@NMWCNT) can improve the specific capacity of this composite material, as can be seen from TEM, SEM, and thermogravimetric analysis. x When MoSe2 is grown on NMWCNT, SiO x / MoSe2 has more exposed edges and a higher content, providing more active sites, thereby improving the specific capacity and cycling stability of the material.

[0090] exist Figure 15 As can be seen in d, C@SiO x The rate performance of / MoSe2-3-1@NMWCNT increases with current density from 0.1 to 10 Ag -1 The specific capacity exhibits a gradual decreasing trend. This is true when the current density is 0.1, 0.2, 0.4, 0.8, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, and 10.0 Ag. -1 At that time, the discharge specific capacities were 720, 644, 588, 536, 516, 464, 434, 410, 395 and 347 mAh g, respectively. -1 When the current density recovers to 0.1Ag -1At that time, its discharge capacity recovers to 660mAh g. -1 This reflects good reversibility. Especially in... Figure 15 C@SiO can be observed in e. x The long-cycle performance of / MoSe2-3-1@NMWCNT at 5Ag -1 It can still maintain 353mAh g after 300 cycles. -1 It exhibits high specific capacity and good capacity retention. It is compatible with C@MoSe2 and C@SiO2. x @NMWCNT、C@SiO x Compared to the three materials MoSe2@C, C@SiO x / MoSe2-3-1@NMWCNT composite material will have high capacity SiO2 x It combines with MoSe2 to form SiO x / MoSe2, grown on NMWCNT, provides more active sites for sodium ion storage, improving the capacity as a SIB electrode. At the same time, the carbon layer coating also alleviates the volume change of the composite material during charge and discharge, improving its cycle stability.

[0091] Figure 17 ab SEM images reflect C@SiO x The thickness change of the / MoSe2-3-1@NMWCNT composite material used as the SIB electrode before and after charge and discharge. The results show that the C@SiO2 composite material... x The morphology of / MoSe2-3-1@NMWCNT remained stable, with the average electrode thickness increasing from 17.8 μm to 20.9 μm, and no significant structural collapse occurred. This demonstrates that C@SiO x The unique three-layer heterojunction structure of the / MoSe2-3-1@NMWCNT composite material buffers the volume changes caused by charging and discharging, thereby improving the performance of C@SiO2. x Stability of / MoSe2-3-1@NMWCNT composite material and its long-cycle performance as a SIB electrode material.

[0092] In summary, we have demonstrated a simple method for constructing C@SiO based on NMWCNT. x A method for synthesizing / MoSe2@NMWCNT three-layer heterojunction materials. The three-layer heterojunction structure of this composite system can effectively buffer SiO2. x The volume change of / MoSe2 maintains the stability of the electrode structure, thereby improving the electron and Na content. + Ionic conductivity, and SiO xUniformly dispersed within the MoSe2 nanosheet framework, it provides a high specific capacity. When used as a stand-alone electrode, the optimized C@SiO... x The / MoSe2-3-1@NMWCNT material offers a high specific capacity (500 mAg). -1 620mAh g -1 ) and good cycling stability (5000mA g) -1 373mAh g after 2000 cycles -1 353mAh g after 3000 cycles -1 The newly developed synthesis method can be used to design and construct electrode materials for SIBs.

Claims

1. A method for synthesizing C@SiO x / MoSe2@NMWCNT material based on NMWCNT, characterized in that, Comprise the following steps: S1: dissolve molybdenum pentachloride in the first ethylene glycol solution to form a molybdenum-based metal organic complex, and then add triphenylchlorosilane and the second ethylene glycol solution to the molybdenum-based metal organic complex to form a molybdenum-based silicon metal organic complex; S2: add NMWCNT to the molybdenum-based silicon metal organic complex and perform ultrasonic treatment to uniformly disperse the NMWCNT and uniformly adsorb the molybdenum-based silicon metal organic complex on the surface of the NMWCNT, thereby obtaining a dispersed solution; S3: Calcination of the dispersed solution under inert gas atmosphere to produce C@SiO x / MoSe2@NMWCNT material, wherein 1≤X≤2.

2. The NMWCNT based construction C@SiO x The synthesis method of the MoSe2@NMWCNT material is characterized in that, In step S1, the mass-volume ratio of molybdenum pentachloride to the first ethylene glycol solution is 27.2:5.6 mg / ml, and the mass ratio of molybdenum pentachloride to triphenylchlorosilane is 27.2:29.4-147.

3. The NMWCNT based construct C@SiO x The synthesis method of the MoSe2@NMWCNT material is characterized in that, In step S1, the volume ratio of the first ethylene glycol solution to the second ethylene glycol solution is 5.6:

17.

4. The NMWCNT based construct C@SiO x The synthesis method of the MoSe2@NMWCNT material is characterized in that, In step S2, the mass ratio of NMWCNT to triphenylchlorosilane is 8:29.4-147.

5. The NMWCNT based construct C@SiO x The synthesis method of the MoSe2@NMWCNT material is characterized in that, In step S3, the heating rate during calcination is 5℃ / min.

6. The NMWCNT based construct C@SiO x The synthesis method of the MoSe2@NMWCNT material is characterized in that, In step S3, the calcination method is: heating at 80℃ for 4h, heating at 180℃ for 3h, and heating at 800℃ for 4h.

7. The NMWCNT based construct C@SiO x The synthesis method of the MoSe2@NMWCNT material is characterized in that, In step S2, the ultrasonic treatment is performed for 4h, and in step S3, the inert gas is argon.

8. Use of NMWCNTs for the construction of C@SiO x / MoSe2@NMWCNT materials, characterized by, The C@SiO x The synthesis method of the / MoSe2@NMWCNT material is as described in any one of claims 1-7, and the C@SiO x The / MoSe2@NMWCNT material is used as a raw material for preparing an electrode material.

9. The NMWCNT based construct C@SiO x Use of the C@SiO The electrode material preparation method is as follows: C@SiO x / MoSe2@NMWCNT material is mixed with acetylene black and carboxymethyl cellulose at a mass ratio of 4:1:1, ground, stirred with water and ethanol as solvents to form a slurry, and then uniformly coated on a copper foil to obtain the electrode material.

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