Synthesis method and application of c@mos2 / snse2 / cnt(o) three-layer nanocomposite heterojunction material

Abstract

The application discloses a synthesis method of a lithium ion battery negative electrode material, and particularly relates to a synthesis method of C@MoSe2 / SnSe2@CNT(O) material based on oxygen-doped carbon nanotube CNT(O). The nanosheet loaded with MoSe2 and SnSe2 doped with each other on the surface of CNT(O) can relieve material volume expansion, provide more active sites, and thus obtain higher capacity and better long cycle stability. The application takes molybdenum pentachloride, dihydroxy butyl tin chloride, Se, CNT(O) and ethylene glycol as raw materials, and synthesizes C@MoSe2 / SnSe2@CNT(O) nanocomposite heterojunction material through ultrasonic dispersion and subsequent calcination method. Compared with similar products, the method has the advantages of simple steps, high safety, low cost, obvious nanosheet morphology characteristics of the prepared product, more active sites provided by the CNT(O) coated inside, high capacity, good cycle stability and obvious advantages under large current (30 Ag ‑1 of current density, capacity is kept at 667 mA h g ‑1 after 10000 times of long cycle), and is beneficial to realize the large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite material preparation, and relates to the synthesis of a MoSe2 / SnSe2@CNT(O) composite material formed by co-growing MoSe2 nanosheets and SnSe2 nanosheets on CNT(O), which is applied to the negative electrode of lithium-ion batteries. Background Technology

[0002] In recent years, environmental pollution and the scarcity of non-renewable resources such as petroleum and coal have become increasingly serious, leading people to focus on electrochemical energy storage devices, including lead-acid batteries, lithium-sulfur batteries, lithium-ion batteries, sodium-ion batteries, and supercapacitors. Among these, lithium-ion batteries, with their high energy density, high voltage platform, and long cycle life, are one of the most mature and widely used electrochemical energy storage technologies.

[0003] Negative electrode materials for lithium-ion batteries include carbon materials, such as graphene (with a theoretical capacity of 372 mAh / g), and non-carbon materials, such as silicon-based, molybdenum-based, tin-based, and nitride-based materials. With the development of science and technology, the relatively low theoretical capacity of graphene has become insufficient for practical applications. Although silicon-based, germanium-based, and tin-based alloy anodes have advantages such as abundance, relatively low lithiation voltage, and high lithium reserves, the significant destructive impact of volume expansion during cycling and their low intrinsic electronic conductivity hinder the further application of these alloy anodes. To address the issues of low energy capacity and cycle stability, the development of new high-capacity and low-cost electrode materials is crucial.

[0004] Both MoSe2 and SnSe2 belong to the transition metal chalcogenides and have been extensively studied due to their high specific capacity, excellent rate performance, and similar two-dimensional layered structure. MoSe2 is a compound with a sandwich structure, where the layers are connected by Se-Mo-Se covalent bonds within the plane and weak van der Waals forces couple the layers together, providing channels for atoms to freely insert and extract between the layers. MoSe2 has a special layered structure similar to graphite, with an interlayer spacing of approximately 0.647 nm. The strong metallic properties of MoSe2 can effectively reduce the Gibbs free energy during structural transformation, which is beneficial for the insertion and extraction of lithium ions between the layers, resulting in stronger electrochemical activity and showing great potential in the field of lithium-ion batteries. The theoretical capacity of pure MoSe2 is 422 mAh / g; however, in applications, various factors such as material conductivity, volume expansion, and electrolyte stability can reduce the actual capacity. Researchers often improve the lithium storage performance of MoSe2 by constructing heterojunctions, element doping, and material compositing to bring it closer to the theoretical capacity.

[0005] Tin-based materials are considered promising new materials that could potentially replace traditional graphite anodes due to their high theoretical capacity (Sn / SnO / SnO2, 994 / 875 / 1494 mAh / g) and natural abundance. However, pure Sn-based materials also suffer from high volume expansion and poor cycle stability. Combining the transition metal element Mo with Sn to form a binary alloy system is an effective material modification strategy. This Sn / Mo binary alloy system has Li provided by the transition metal. + The channel and stable framework, along with the good ductility of the transition metal, can reduce the structural collapse caused by volume expansion during lithiation, thus enabling it to exhibit good electrochemical behavior in high-current, long-cycle systems.

[0006] Studies have shown that the nanoscale diameter of carbon nanotubes and the interlacing gaps between them endow carbon nanotubes with excellent chemical and physical properties and lithium encapsulation performance. Therefore, the short path and shallow depth during lithiation / delithiation, and the low polarization during high-current charge and discharge, have a significant impact on the improvement of current density and charge and discharge capacity. Specifically, the excellent electrochemical performance of CNTs is mainly due to several reasons: (1) The high porosity of CNTs makes Li + (2) Li + It can be embedded in multiple locations such as tube diameter, tube core, and inter-tube gap; (3) The nanoscale tube wall can accelerate Li + Migration and diffusion from the inside and outside of CNTs; (4) The excess energy from the hydrogen-to-carbon ratio limits the bonding energy between lithium and adjacent hydrogen atoms; (5) In carbon nanotubes, a lithium layer may form on the graphite outer surface of the microcrystals; (6) Li on the chair grid points and branch surfaces + They occupy a large market share. Furthermore, the excellent conductivity of CNTs can improve the fast charge and discharge capabilities of lithium-ion batteries, making them suitable as anode materials.

[0007] Against this background, growing MoSe2 and SnSe2 nanosheets on O-doped CNTs improves the material's tendency to expand and break, creates more active sites, and improves conductivity, thereby enhancing the material's electrochemical performance.

[0008] In this invention, we first synthesized a Mo-based metal complex solution, then added organotin to it for further reaction with the metal complex, obtaining a Mo-based / Sn-based metal complex mixed solution. After ultrasonic treatment and calcination under an inert gas atmosphere, we successfully prepared a C@MoSe2 / SnSe2@CNT(O) composite material. The product composition was confirmed by X-ray diffraction. The prepared C@MoSe2 / SnSe2@CNT(O) product powder was then used for slurry preparation, coating, and drying to obtain electrode sheets. These sheets were then used as negative electrode materials to assemble lithium-ion batteries, and their electrochemical performance was tested. (0.1 A g) -1 At a current density of 1765.55 mA hg, the initial discharge specific capacity reached 1765.55 mA hg. -1 After 100 cycles, the capacity reached 1125.67 mAh g. -1 Increase the test current density to 0.5 A g. -1 2 A g -1 5 A g -1 10 A g -1 20 A g -1 With 30 A g -1 Its initial discharge capacities were 2089.28 mA h g⁻¹ and 1994.45 mA h g⁻¹, respectively. -1 1492.75 mA hg -1 2314.49 mAh g -1 1909.99 mA hg -1 1839.89 mA hg -1 This indicates that the material possesses a generally high initial specific capacity. Notably, this material exhibits significant advantages in high current and long cycling performance. At 20 A g... -1 At a current density of 600 mA hg, the discharge specific capacity at the 6th cycle is 600 mA hg. -1 After 2000 cycles, the capacity gradually increased to 1205 mA hg. -1 After 10,000 long cycles, the capacity remained at 689 mA hg. -1 At 30A g -1 At a current density of 530 mA hg, the discharge specific capacity at the 6th cycle is 530 mA hg. -1 After 2500 cycles, the capacity gradually increased to 920 mA hg. -1 After 10,000 long cycles, the capacity remained at 667 mA hg. -1The high discharge specific capacity and long cycle life of this material as a negative electrode for lithium-ion batteries can be attributed to the following factors: First, the MoSe2 and SnSe2 nanosheets in the system have high theoretical capacity, which can improve the high specific capacity of the composite material. Second, MoSe2 nanosheets and SnSe2 are two-dimensional layered materials, which can increase the specific surface area of ​​the composite material, thus enhancing the specific capacity of Li-ion batteries. + The increased transport capacity of nanochannels enhances their adsorption, storage, and desorption capabilities in composite materials. Third, oxidized carbon nanotubes (CNT(O)) act as a carbon framework in composite materials, improving both the conductivity and stability of the material, thus increasing its cycle life.

[0009] This invention provides a simple preparation method for C@MoSe2 / SnSe2@CNT(O) materials, which have significant advantages as a negative electrode material for lithium-ion batteries, and provide new ideas for the development of negative electrode materials for lithium-ion batteries. Summary of the Invention

[0010] The purpose of this invention is to develop a high-performance lithium-ion battery anode material, and to propose a synthesis method for C@MoSe2 / SnSe2@CNT(O) material based on CNT(O).

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A method for synthesizing C@MoSe2 / SnSe2@CNT(O) based composite materials, the preparation method of which includes the following steps:

[0013] S1. First, add a certain amount of molybdenum pentachloride to an ethylene glycol solution to form a molybdenum-based organometallic complex. The optimal effect is achieved by adding 15-25 ml of ethylene glycol. After the molybdenum-based organometallic complex is completely formed, add another certain amount of ethylene glycol solution, followed by dihydroxybutyltin chloride, to form a tin-based organometallic complex. The optimal effect is achieved by adding 5-15 ml of ethylene glycol.

[0014] S2. Add CNT(O) to the solution and place it in an ultrasonic device for ultrasonication to make the nanotubes uniformly dispersed and the molybdenum-based / tin-based organometallic complex uniformly adsorbed on the CNT(O) surface.

[0015] S3. Take out the above solution and put it into a ceramic boat containing selenium powder, and then transfer it to a tube furnace containing Ar atmosphere for calcination at a heating rate of 4-6℃ / min.

[0016] S4. After ultrasonic and calcination reactions, the Mo and Sn elements in the precursor dispersion are selenized in situ into MoSe2 and SnSe2, while the organic components are converted into carbon materials in situ. CNT(O) is encapsulated inside by these three components, resulting in C@MoSe2 / SnSe2@CNT(O) nanocomposite material.

[0017] In S1, ethylene glycol is added in portions, while dihydroxybutyltin chloride is added while stirring.

[0018] In S1, the concentration of molybdenum pentachloride is 0.01~0.03 mmol / mL. -1 .

[0019] In S1, the concentration of dihydroxybutyltin chloride is 0.005~0.02 mmol / mL. -1 .

[0020] In S1, the molar ratio of molybdenum pentachloride to dihydroxybutyltin chloride is 2 to 1.

[0021] In S1, the concentration of selenium is 0.08~0.1 mmol / mL. -1 .

[0022] In S2, the concentration of CNT(O) is 0.4–0.6 mg / mL. -1 .

[0023] In S2, ultrasound for 2–4 hours enhances the dispersion effect of CNT(O).

[0024] In S3, the protective atmosphere used is argon. The temperature is maintained at 60–100℃ for 3–5 hours, then raised to 130–300℃ and maintained for 3–5 hours. Finally, the temperature is raised to 800℃ and calcined for 4 hours, followed by natural cooling to room temperature.

[0025] In S4: The composite material is a C@MoSe2 / SnSe2@CNT(O) nano-trilayer composite heterojunction material. MoSe2 and SnSe2 nanosheets are doped and grown around CNT(O). At the same time, the carbon layer formed after the organic matter is carbonized coats the surface of MoSe2 and SnSe2, thereby forming a three-layer heterojunction structure of carbon layer-transition metal dichalcogenide nanosheet layer-carbon nanotube layer. The carbon nanotube layer can increase conductivity and stabilize the structure.

[0026] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0027] This invention utilizes molybdenum pentachloride, dihydroxybutyltin chloride, Se, CNT(O), and ethylene glycol as raw materials to prepare C@MoSe2 / SnSe2@CNT(O) nanocomposite three-layer heterojunction materials through stirring, ultrasonic dispersion, and high-temperature annealing under an inert gas atmosphere. Compared to similar products, this method has a simple preparation process, and the product exhibits excellent performance in electrochemical tests, demonstrating high discharge specific capacity and long-term cycle stability (at 30 A g). -1 At current density, it reaches 920 mA hg after 2500 cycles. -1 High discharge specific capacity; after 10,000 cycles, it still has 667 mA hg. -1 (With a specific capacity close to that of the initial discharge), this provides a feasible approach for the large-scale production of advanced anode materials for lithium-ion batteries. Detailed Implementation

[0028] 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.

[0029] Unless otherwise specified, the reaction raw materials and catalysts involved in the following examples are all commercially available reagents.

[0030] 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.

[0031] In Example 1, the construction of C@MoSe2 heterojunction composite material and its lithium storage performance were studied. The preparation method of this composite material includes the following steps:

[0032] S1. Dissolve 150-170 mg of molybdenum pentachloride in 15-25 mL of ethylene glycol to generate a molybdenum-based organometallic complex.

[0033] S2. Sonicate the molybdenum-based organometallic complex solution for four hours until the solution is homogeneous;

[0034] S3. Take out the above solution and put it into a ceramic boat containing 130~150 mg Se powder. Then transfer it to a tube furnace containing Ar atmosphere and heat it in stages at 80 ℃, 180 ℃ and 800 ℃, respectively, and hold for 4 h. The heating rate is 5 ℃ / min.

[0035] S4. After ultrasonic and calcination reactions, 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.

[0036] 2. Further research on the construction of C@MoSe2 heterojunction composite materials and their lithium storage performance as required above, characterized in that, in S1, the temperature during the addition process is room temperature.

[0037] 3. Further research on the construction of C@MoSe2 heterojunction composite materials and their lithium storage performance as required above, characterized in that the composite material is C@MoSe2, which is a heterojunction structure with carbon coated on the surface of MoSe2, and MoSe2 is a few-layer nanosheet structure.

[0038] 4. Further, C@MoSe2 nanocomposite heterojunction material, acetylene black, and carboxymethyl cellulose (CMC) are mixed and ground in a mass ratio of (4:1:1) and then transferred to a volumetric flask. Water and ethanol are added to the mixture, and after thorough stirring and mixing, it is coated onto copper foil, dried, and cut to obtain the working electrode.

[0039] In Example 2, the construction of C@SnSe2 heterojunction composite material and its lithium storage performance were studied. The preparation method of this composite material includes the following steps:

[0040] S1. Take 60-80 mg of dihydroxybutyltin chloride, stir and add 10 mL of ethylene glycol to generate a tin-based organometallic complex;

[0041] S2. Stir the solution for 4 hours to completely dissolve the dihydroxybutyltin chloride in ethylene glycol, and then transfer the solution to an ultrasonic device for ultrasonication.

[0042] S3. Take out the above solution and put it into a ceramic boat containing 60~80 mg of Se powder. Then transfer it to a tube furnace containing Ar atmosphere and heat it in stages at 80 ℃, 180 ℃ and 800 ℃, respectively, and hold for 4 h. The heating rate is 5 ℃ / min.

[0043] S4. After ultrasonication and calcination, the Sn element in the precursor dispersion is selenized in situ to SnSe2, and the organic components are converted into carbon materials in situ, ultimately generating C@SnSe2 nanocomposite heterojunction materials.

[0044] 2. A further method for synthesizing a C@SnSe2 heterojunction composite material according to the above requirements, characterized in that the temperature during the addition process in S1 is room temperature, i.e., 20-30°C.

[0045] 3. Further research on the construction of C@SnSe2 heterojunction composite materials and their lithium storage performance as required above, characterized in that the composite material is C@SnSe2, which is a heterojunction structure with carbon coated on the surface of SnSe2, and SnSe2 is a few-layer nanosheet structure.

[0046] 4. Further, the obtained C@SnSe2 heterocomposite material was mixed and ground with acetylene black and carboxymethyl cellulose (CMC) at a mass ratio of 4:1:1, and then transferred to a volumetric flask. Water and ethanol were added to the mixture, and after thorough stirring and mixing, it was coated onto copper foil, dried, and cut to obtain the working electrode.

[0047] In Example 3, the construction of C@MoSe2 / SnSe2 heterojunction composite material and its lithium storage performance were studied. The preparation method of this composite material includes the following steps:

[0048] S1. Dissolve 150-170 mg of molybdenum pentachloride in 15-25 mL of ethylene glycol to form a molybdenum metal organic complex. Then stir and add 90-110 mg of dihydroxybutyltin chloride. Add 5-15 mL of ethylene glycol solvent to the above solution and wait for the reaction to be complete to form a tin-based metal organic complex.

[0049] S2. Stir the solution for 4 hours to completely dissolve the dihydroxybutyltin chloride in ethylene glycol, and then transfer the solution to an ultrasonic device for ultrasonication.

[0050] S3. Take out the above solution and put it into a ceramic boat containing 210~230 mg Se powder. Then transfer it to a tube furnace containing Ar atmosphere and heat it in stages at 80 ℃, 180 ℃ and 800 ℃, respectively, and hold for 4 h. The heating rate is 5 ℃ / min.

[0051] S4. After ultrasonication and calcination, the Mo element in the precursor dispersion is selenized in situ to MoSe2, the Sn element is selenized in situ to SnSe2, and the organic components are converted into carbon materials in situ, ultimately generating C@MoSe2 / SnSe2 nanocomposite heterojunction materials.

[0052] 2. A further method for synthesizing a C@MoSe2 / SnSe2 heterojunction composite material according to the above requirements, characterized in that the temperature during the addition process in S1 is room temperature, i.e., 20-30°C.

[0053] 3. Further, a method for synthesizing a C@MoSe2 / SnSe2 heterocomposite material according to the above requirements, characterized in that: the composite material is a C@MoSe2 / SnSe2 carbon-coated composite nanosheet material, that is, MoSe2 and SnSe2 nanosheets are co-grown, and carbon is coated on the surface of MoSe2 and SnSe2 nanosheets during calcination to form a carbon composite material.

[0054] 4. Further, the obtained C@MoSe2 / SnSe2 heterocomposite material was mixed and ground with acetylene black and carboxymethyl cellulose (CMC) at a mass ratio of 4:1:1, and then transferred to a volumetric flask. Water and ethanol were added to the mixture, and after thorough stirring and mixing, it was coated onto copper foil, dried, and cut to obtain the working electrode.

[0055] Example 4 describes a method for synthesizing C@MoSe2 / SnSe2@CNT(O) based materials and its related lithium storage performance. The preparation method of this composite material includes the following steps:

[0056] S1. Dissolve 150-170 mg of molybdenum pentachloride in 15-25 mL of ethylene glycol. After the reaction is complete by sonication for 20-40 minutes, add 60-80 mg of dihydroxybutyltin chloride while stirring and add 5-15 mL of ethylene glycol. Stir until the reaction is complete to form a mixed solution of molybdenum-based metal complex and tin-based metal complex.

[0057] S2. Add 10-30 mg of CNT(O) to the solution and sonicate for four hours until evenly dispersed;

[0058] S3. Take out the above solution and put it into a ceramic boat containing 210~230 mg Se powder. Then transfer it to a tube furnace containing Ar atmosphere and heat it in stages at 80 ℃, 180 ℃ and 800 ℃, respectively, and hold for 4 h. The heating rate is 5 ℃ / min.

[0059] S4. After ultrasonication and calcination, the Mo and Sn elements in the precursor dispersion are selenized in situ into MoSe2 and SnSe2, and then grown on CNT(O). Meanwhile, the organic components are converted in situ into carbon materials that coat the outer layer of the MoSe2 and SnSe2 nanosheets, ultimately generating a C@MoSe2 / SnSe2@CNT(O) three-layer nanocomposite heterojunction material.

[0060] 2. A method for synthesizing C@MoSe2 / SnSe2@CNT(O) materials based on CNT(O) according to the above requirements, wherein in S1, the optimal molar ratio of molybdenum pentachloride to dihydroxybutyltin chloride in this example is 2:1;

[0061] 3. A method for synthesizing C@MoSe2 / SnSe2@CNT(O) materials based on CNT(O) according to the above requirements, characterized in that, in step S1, the temperature during the addition process is room temperature, i.e., 20-30°C;

[0062] 4. A method for synthesizing C@MoSe2 / SnSe2@CNT(O) materials based on CNT(O) according to the above requirements, characterized in that: the composite material is a C@MoSe2 / SnSe2@CNT(O) nanotrilayer composite heterojunction material (a trilayer heterojunction structure formed by growing MoSe2 / SnSe2 nanosheets around CNT(O) and simultaneously coating the surface of MoSe2 / SnSe2 nanosheets with carbon).

[0063] 5. Further, the obtained C@MoSe2 / SnSe2@CNT(O) heterocomposite material was mixed and ground with acetylene black and carboxymethyl cellulose (CMC) at a mass ratio of 4:1:1, and then transferred to a volumetric flask. Water and ethanol were added to the mixture, and after thorough stirring and mixing, it was coated onto copper foil, dried, and cut to obtain the working electrode.

[0064] The following uses Examples 1-4 as representatives for characterization:

[0065] The structures of C@MoSe2, C@SnSe2, C@MoSe2 / SnSe2 and C@MoSe2 / SnSe2@CNT(O) were characterized using SEM and TEM techniques. 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 a carbon layer, the number of MoSe2 layers was relatively small (around 10 layers). HAADF-STEM images and corresponding elemental maps showed a uniform distribution of Mo, Se, and C elements in the nanosheet structure, further confirming the carbon coating on the MoSe2 nanosheets. The formation of few-layered 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.

[0066] Figure 3The morphologies of C@MoSe2 (a,d), C@SnSe2 (b,e), and C@MoSe2 / SnSe2 (c,f) are clearly shown. All three are stacked nanosheets. The difference is that the pure MoSe2 and SnSe2 nanosheets are larger in size and more prone to aggregation, presenting a clump-like shape, while the C@MoSe2 / SnSe2 nanosheets are more uniform in size and have better dispersibility. Figure 4 The morphology of C@MoSe2 / SnSe2@CNT(O) is shown. At low magnification, figures a, b, and c show a nanosheet morphology similar to that of C@MoSe2, C@SnSe2, and C@MoSe2 / SnSe2. However, the smaller and more uniform MoSe2 and SnSe2-doped nanosheets are more compactly attached to the carbon nanotubes. This dense nanosheet structure not only shortens the distance between the inner MoSe2 layer and the outer carbon surface but also increases the surface area in contact with the electrolyte. With the shortened lithium-ion migration distance, the utilization rate of the active material is improved, thereby enhancing battery performance. More notably, carbon nanotubes extending from the interior of the material appear at the center of figure c. Magnifying this further, figure d reveals that multiple layers of nanosheets are grown around the CNT(O), confirming that the material structure is a heterojunction of inner carbon nanotubes and outer nanosheets. Subsequently, to verify the elemental distribution and content of C@MoSe2 / SnSe2@CNT(O), HRTEM testing was performed, and the EDS-mapping elemental distribution test results are as follows: Figure 5 As shown in the figure, Mo, Sn, Se, and O are uniformly distributed in the material, and the relative contents of each element are as follows: Figure 5 As shown, the relative content of Mo is 5.08%, the relative content of Sn is 0.13%, and the relative content of Se is 10.44%. It can be seen that the outer nanosheets are mainly MoSe2, with a small amount of SnSe2 doped in them.

[0067] TEM was performed on C@MoSe2 / SnSe2@CNT(O) to determine the lattice structure of the material. Figure 7 As can be seen from images a and b, this material exhibits a very distinct heterojunction structure, with an internal carbon nanotube network and an outer layer of attached nanosheets, displaying obvious molybdenum selenide lattice fringes. This further verifies the composition and structure of the material.

[0068] Based on SEM and TEM characterization of the four materials, all synthesized materials exhibit a stacked nanosheet morphology with an outer carbon layer, successfully synthesizing a heterojunction structure. The difference lies in the fact that the C@MoSe2 / SnSe2@CNT(O) material is internally filled with interwoven carbon nanotube structures, enabling it to provide Li + Provides more internal channels. To further understand the material properties, explain Li +The storage mechanism was investigated, and the materials were analyzed by XRD, thermogravimetric analysis, Raman, and XPS to further verify the properties of the synthesized materials. Figure 8 Image a shows the XRD patterns of C@MoSe2, C@SnSe2, and C@MoSe2 / SnSe2@CNT(O). XRD diffraction clearly reveals the crystal structure of the materials. All peaks in C@MoSe2 (represented by purple) conform to the hexagonal phase of MoSe2 (JCPDS 29-0914) in space group P63 / mmc, indicating that the synthesized material is primarily MoSe2. The yellow C@SnSe2 conforms to JCPDS 23-0602, while the characteristic peaks of 13.6◦, 37.9◦ and 55.9◦ in the C@MoSe2 / SnSe2@CNT(O) composite material can be well hidden on the (002), (103) and (110) planes of the hexagonal MoSe2 (PDF# 29-0914), and the broad diffraction peaks of 11-15◦, the strong diffraction peak of 31◦ and the diffraction peak of 42.1◦ can be assigned to the (001), (101) and (003) planes of the hexagonal SnSe2 (PDF# 23-0602). Figure 8 b and 8c are the Raman characterization results of C@MoSe2, C@SnSe2, C@MoSe2 / SnSe2, and C@MoSe2 / SnSe2@CNT(O). From the spectra, the positions of the D and G peaks are clearly visible at 1343 cm⁻¹. -1 and 1594 cm -1 , Figure 8 c), 1350 and 1580 cm -1 The two characteristic peaks on the left and right reflect the degree of defects in the material, representing the d-bonds of disordered carbon and the g-bonds of graphene carbon, respectively. The d-bond to g-bond strength ratios (ID / IG) of the C@MoSe2, C@SnSe2, C@MoSe2 / SnSe2, and C@MoSe2 / SnSe2@CNT(O) composites are all close to 1. Among them, the ID / IG of C@MoSe2 / SnSe2@CNT(O) is 0.98, indicating that C@MoSe2 / SnSe2...

[0069] In the @CNT(O) composite material, the disordered carbon and graphene carbon components are roughly equal. Additionally, 238 cm... -1 and 283.1 cm -1 These are the out-of-plane (A) of Mo-Se. 1g ) and in-plane (E 1 2g atomic vibration modes ( Figure 8 c). The (A) of C@MoSe2, C@SnSe2, and C@MoSe2 / SnSe2@CNT(O) can be observed. 1g) and (E 1

[0070] 2g The strength ratios of the two are not significantly different, indicating that the carbon outer layer coating does not have a significant impact on the layered structure of MoSe2.

[0071] The surface chemical composition and valence states of the C@MoSe2 / SnSe2@CNT(O) composite material were investigated using X-ray photoelectron spectroscopy (XPS). The full spectrum was obtained in the range of 0 eV to 1200 eV. Figure 9 a) The presence of carbon, oxygen, molybdenum, tin, and selenium is clearly shown. Figure 9 b shows that the C1s peak mainly exists in three forms: 284.8 eV represents sp2 CC / C=C, 286.7 eV represents CO, and 288.9 eV represents C=O. The peaks for Mo, Sn, and Se elements in the composite material are shown... Figure 8 In d, 8e, and 8f, the 225.7 eV and 228.9 eV peaks in the Mo 3d spectrum are the Mo 3d5 / 2 and 3d3 / 2 signal peaks, respectively, belonging to Mo. 4+ The characteristic peaks are not obvious in the Sn 3d spectrum. The relatively strong peaks at 486.7 eV and 495.6 eV are the Sn 3d5 / 2 and 3d3 / 2 signal peaks, belonging to the Sn 3d5 / 2 and 3d3 / 2 spectrum. 4+ The characteristic peaks and low intensities may be due to the relatively small initial amount of Sn, only half the molar amount of Mo. Additionally, the thicker outer C layer during carbonization may also contribute to the less prominent signal peaks. In the Se 3d spectrum, the Se 3d peaks at 50.8 eV (Se3d5 / 2) and 51.6 eV (Se 3d3 / 2) correspond to Se... 2+ The peak of the state.

[0072] To further estimate the carbon content in the samples, thermogravimetric analysis (TAG) was performed on C@MoSe2, C@SnSe2, C@MoSe2 / SnSe2, and C@MoSe2 / SnSe2@CNT(O). The results are as follows: Figure 10 As shown, after heating in air, MoSe2 and SnSe2 generate MoO3, SnO2, and SeO2 at 400°C, resulting in a slight increase in weight. Weight loss then begins around 400°C, due to the oxidation of the carbon material and the evaporation of SeO2. Among the thermogravimetric curves of the four materials, the thermogravimetric curve of C@MoSe2 / SnSe2@CNT(O) is significantly different from the other three, indicating that it has higher carbon, Mo, and Sn content.

[0073] The electrochemical performance of C@MoSe2, C@SnSe2, C@MoSe2 / SnSe2, and C@MoSe2 / SnSe2@CNT(O) is influenced by their unique nanosheet morphology, bonding methods, and composition. To evaluate the lithium storage performance of these materials, they were assembled into coin cells for electrochemical testing. Figure 11 Figure a shows the cyclic voltammograms (CV) of the MoSe2 / SnSe2@C electrode for the first four cycles in a lithium-ion battery at a scan rate of 0.1 mV s−1, within the range of 0.01 to 3.0 V. As can be seen in the figure, distinct reduction peaks are observed at 0.90, 0.68, and 0.43 V during the first scan discharge. The first peak at 0.90 V is Li... +

[0074] It reacts with MoSe2 to convert to Li x The peak at 0.68 V is caused by MoSe2, while the peak at Li is caused by Li. + Insertion into the SnSe2 layer and an alloying reaction occurs to form Na. 15 The peak at 0.43V was caused by Sn4, but the broad scan peak did not appear during the subsequent discharge process. This may be due to some Li x MoSe2 is further reduced to Mo and Li2Se, and the electrolyte decomposition forms a solid electrolyte interphase (SEI) film. Reduction peaks were observed at 1.9 V and 1.3 V in the subsequent three cycles, due to the reduction of Li. + The peaks at 1.4V and 2.1V during charging are due to the regeneration of MoSe2 and SnSe2. Since the CV curves of the subsequent three cycles almost overlap, it can be determined that the C@MoSe2 / SnSe2@CNT(O) material has good reversibility and stability. Figure 11 b shows the CV curves of the C@MoSe2 / SnSe2@CNT(O) electrode at different scan rates. These curves have very similar redox peaks, but during the reduction process, as the scan rate increases, the electrode is activated, causing the reduction peak to shift slightly. Figure 11 c is the charge-discharge curve of C@MoSe2 / SnSe2@CNT(O). It can be observed from the figure that the discharge capacity gradually decreases with the increase of the number of cycles, which may be due to the formation of the SEI film. Figure 11 Figure d shows the rate performance of C@MoSe2 / SnSe2@CNT(O) as a lithium-ion battery anode material, as the current density increases from 0.1 A g. -1 Increase to 10 A g -1 The specific capacity also decreases accordingly, at 10 A g -1At current density, the specific capacitance is 1454 mA hg -1 Gradually reduced to 1308, 1138, 960, 921, 893, 836, 761, 732, 686, 534 mA hg -1 When the current density returns to 0.1 A g -1 At that time, the capacity returned to 1491 mA hg. -1 This demonstrates that the material exhibits excellent rate performance. C@MoSe2, C@SnSe2, C@MoSe2 / SnSe2, and C@MoSe2 / SnSe2@CNT(O) were tested at 0.5 A g. -1 Cyclic stability and specific capacity at current density, such as Figure 11 As shown in Figure e, the capacity of C@MoSe2 / SnSe2@CNT(O) gradually increases over 150 cycles, eventually reaching 1505 mA hg. -1 It is significantly better than C@MoSe2 (1105 mA hg). -1 ), C@SnSe2 (376.5 mA hg -1 Although C@MoSe2 / SnSe2 (1235 mA hg) -1 Compared to pure C@MoSe2 and C@SnSe2, the capacity is increased, but still lower than that of C@MoSe2 / SnSe2@CNT(O). This is attributed to the heterojunction structure of C@MoSe2 / SnSe2 doped nanosheets on the outer layer and oxygen-doped carbon nanotubes (CNT(O)) inside, which can provide abundant active sites, and the internal carbon can stabilize the structure and provide material stability. To optimize the ratio of MoCl5 to dihydroxybutyltin chloride for best electrochemical performance, a series of C@MoSe2 / SnSe2@CNT(O) materials were prepared using the same procedure. The molar ratios of MoCl5 to dihydroxybutyltin chloride were adjusted to 0.3:0.3, 0.6:0.3, and 0.9:0.3, and named C@MoSe2 / SnSe2@CNT(O)-1-1, C@MoSe2 / SnSe2@CNT(O)-2-1, and C@MoSe2 / SnSe2@CNT(O)-3-1, respectively. Electrochemical performance tests were conducted on all three materials. At a current density of 0.5 A g⁻¹, the specific capacity and cycle stability of the three materials were as follows: Figure 11 As shown in f, after 150 cycles, the discharge specific capacity of C@MoSe2 / SnSe2@CNT(O)-1-1 is 493.8 mA hg. -1 The discharge specific capacity of C@MoSe2 / SnSe2@CNT(O)-2-1 is 1505.1 mA hg. -1The discharge specific capacity of C@MoSe2 / SnSe2@CNT(O)-3-1 is 737.2 mA hg. -1 The optimal molar ratio is 0.6:0.3. The reason for this phenomenon may be that when the molar ratio is 0.3:0.3, the content of MoSe2, the main contributor to capacity, is low, resulting in capacity decay. When the molar ratio is 0.9:0.3, although the content of MoSe2 increases, the thickness of the outer attached nanosheets also increases, causing nanosheet stacking, which hinders the transport of Li+ and thus reduces capacity.

[0075] Finally, to investigate the electrochemical performance of C@MoSe2 / SnSe2@CNT(O) under high current density and long cycle time, it was tested as a lithium-ion battery anode material at a current density of 10 A g. -1 20 A g -1 30 A g -1 The results of a charge-discharge test with 10,000 cycles are as follows: Figure 12 As shown in the figure, the electrochemical behavior of this material is stable under high current density, and the capacity reaches its maximum at around 2000 cycles, which is 1308.21 mA hg. -1 1205.78 mA hg -1 920.14 mA hg -1 The capacity then decreased steadily, and ultimately, after 10,000 cycles, the capacity remained at 655.33 mA hg. -1 689.06 mA hg -1 667.52 mA hg -1 The capacity retention rates are ~91.1%, 100%, and 100%. The increased capacity and long cycle life may be attributed to the fact that the high current can break through the stacked nanosheets and the intricate network of nanotubes inside, providing more active sites and defects for Li+, thus increasing the capacity. The carbon nanotubes contained inside can greatly alleviate volume expansion and extend battery life.

[0076] Simultaneously, the thickness of the electrode sheets before and after cyclic discharge was measured to assess the degree of material volume expansion, and the results are as follows: Figure 13 As shown in the figure, the electrode thickness is between 34 μm and 39 μm before discharge, and then increases to 38 μm to 40.64 μm. This shows that the increase in electrode thickness is not significant, indicating that the physical structure is relatively stable and the volume expansion is small, which is very beneficial to the stability of the battery.

[0077] In summary, we have demonstrated a simple method for the in-situ synthesis of molybdenum selenide / tin selenide using molybdenum-based and tin-based organic complexes, followed by their attachment and growth onto carbon oxide nanotubes, thus preparing a three-layered C@MoSe2 / SnSe2@CNT(O) three-dimensional nanostructure. The composite system is a heterostructure of C@MoSe2 / SnSe2.

[0078] @CNT(O) three layers can be Li + It provides more active sites and migration channels, and the internal nanotube structure can effectively buffer the volume change of MoSe2 / SnSe2, maintain the stability of the electrode structure, and improve electron and Li content. + Ion conductivity, promoting Li + Reversible storage within it. When used as a standalone electrode in lithium-ion batteries, the C@MoSe2 / SnSe2@CNT(O) material provides a high specific capacity (0.5 A g). -1 1505 mA hg -1 ) and good cycling stability (10 A g) -1 Current density at 10,000 cycles, 655.33 mA hg -1 20 A g -1 Current density 689.06 mA hg over 10,000 cycles -1 30 A g -1 Current density 667.52 mA hg over 10,000 cycles -1 The newly developed synthesis method and electrode materials provide a feasible solution for developing high-capacity, long-cycle anode materials. Attached Figure Description

[0079] Figure 1 Schematic diagram of the preparation process and structure of .C@MoSe2 / SnSe2@CNT(O).

[0080] Figure 2 SEM (a) and TEM (b, c) images of .C@MoSe2.

[0081] Figure 3 SEM images of C@MoSe2, C@SnSe2, and C@MoSe2 / SnSe2 at different magnifications.

[0082] Figure 4 SEM images of .C@MoSe2 / SnSe2 at different magnifications.

[0083] Figure 5 Elemental distribution of .C@MoSe2 / SnSe2@CNT(O) and corresponding EDS-mapping elemental distribution plots.

[0084] Figure 6 EDS-mapping of elemental composition of .C@MoSe2 / SnSe2@CNT(O).

[0085] Figure 7 TEM image of .C@MoSe2 / SnSe2@CNT(O).

[0086] Figure 8 (a) XRD and (b, c) Raman characterization of C@MoSe2 / SnSe2@CNT(O), and XPS fine spectral analysis of C@MoSe2 / SnSe2@CNT(O) (d) Mo 3d; (e) Sn 3d; (f) Se 3d.

[0087] Figure 9 XPS full spectrum (a) and fine spectral analysis of C@MoSe2 / SnSe2@CNT(O) C 1s(b).

[0088] Figure 10 Thermogravimetric analysis (TGA) of C@MoSe2 and C@SnSe 2， Thermal decomposition processes in C@MoSe2 / SnSe2 and C@MoSe2 / SnSe2@CNT(O) composite systems.

[0089] Figure 11 Composite materials C@MoSe2 and C@SnSe 2， Lithium storage performance of C@MoSe2 / SnSe2 and C@MoSe2 / SnSe2@CNT(O). (a) Lithium storage performance of the composite material C@MoSe2 / SnSe2@CNT(O) at 0.1 mV s. -1 (a) CV curves of the composite material C@MoSe2 / SnSe2@CNT(O) at different scan rates (0.2-1.2 mV / s). -1 (c) Charge-discharge curves of composite material C@MoSe2 / SnSe2@CNT(O); (d) Charge-discharge curves of composite material C@MoSe2 / SnSe2@CNT(O) in the range of 0.1-10 A g. -1 Rate performance; (e)C@MoSe2, C@SnSe 2， C@MoSe2 / SnSe2 and C@MoSe2 / SnSe2@CNT(O) composite materials under a current of 0.5 A g−1.

[0090] Figure 12 The composite material C@MoSe2 / SnSe2@CNT(O) at 10, 20, and 30 A g −1 Performance diagram under high current and long cycle conditions.

[0091] Figure 13 In-situ SEM analysis of C@MoSe2 / SnSe2@CNT(O), (a) charging process from open circuit voltage (OCV) 0.001 V to 3.0 V, (b) changes after discharge from OCV 3.0 to 0.001 V.

Claims

1. A synthesis method for constructing a C@MoSe2 / SnSe2@oxygen-doped CNT lithium ion battery anode material based on oxygen-doped CNTs, characterized by, The preparation method of the negative electrode material comprises the following steps: S1, first add molybdenum pentachloride to 15-25 ml of ethylene glycol solution to form a molybdenum-based metal organic complex, and then add 5-15 ml of ethylene glycol solution to the molybdenum-based metal organic complex after the molybdenum-based metal organic complex is completely formed, and then add dihydroxybutyl tin chloride to form a tin-based metal organic complex; the molar ratio of molybdenum pentachloride to dihydroxybutyl tin chloride is 2:1; dihydroxybutyl tin chloride is added while stirring; S2, add oxygen-doped CNT to the solution, and place it in an ultrasonic device for ultrasonic treatment, so that the nanotubes are uniformly dispersed and the molybdenum-based / tin-based organic metal complex is uniformly adsorbed on the surface of the oxygen-doped CNT; S3, take out the solution and place it in a ceramic capsule containing selenium powder, and then transfer it to a tube furnace containing an Ar atmosphere for calcination, with a heating rate of 4-6℃ / min; keep the temperature at 60-100℃ for 3-5h, then raise the temperature to 130-300℃ and keep it for 3-5h, finally raise the temperature to 800℃ for calcination, and keep the calcination time for 4h, and then naturally cool to room temperature; S4, after ultrasonic treatment and calcination reaction, the Mo and Sn elements in the precursor dispersion liquid are in-situ selenized into MoSe2 and SnSe2, and the organic components are in-situ converted into carbon materials, and the oxygen-doped CNT is coated inside by the three components, to obtain a C@MoSe2 / SnSe2@oxygen-doped CNT nanocomposite material; The nanocomposite material is a C@MoSe2 / SnSe2@oxygen-doped CNT nanometer three-layer composite heterojunction material, MoSe2 and SnSe2 nanosheets are doped around the oxygen-doped CNT, and the carbon layer formed after carbonization of the organic matter is coated on the surface of MoSe2 and SnSe2 to form a carbon layer-transition metal dichalcogenide nanosheet layer-carbon nanotube layer three-layer heterojunction structure. 2.The method for synthesizing C@MoSe2 / SnSe2@oxygen-doped CNT lithium ion battery negative electrode material based on oxygen-doped CNT according to claim 1, characterized in that, In the S1, the concentration of the molybdenum pentachloride is 0.01-0.03 mmol mL -1 . 3.The method for synthesizing C@MoSe2 / SnSe2@oxygen-doped CNT lithium-ion battery anode material based on oxygen-doped CNT according to claim 1, characterized in that In the S1, the concentration of the dihydroxybutyl tin chloride is 0.0005-0.02 mmol mL -1 . 4.The method for synthesizing C@MoSe2 / SnSe2@oxygen-doped CNT lithium-ion battery anode material based on oxygen-doped CNT according to claim 1, characterized in that, In S2, the concentration of oxygen-doped CNTs is 0.4-0.6 mg mL -1 .

5. The synthesis method of C@MoSe2 / SnSe2@oxygen-doped CNT lithium ion battery negative electrode material based on oxygen-doped CNT according to claim 1, characterized in that, In S2, ultrasonic treatment for 2-4h enhances the dispersion effect of the oxygen-doped CNT.

Images