Method for synthesizing C (at) SiOx / MoSe2 (at) OMWCNT material based on silicon-molybdenum-based metal complex and application

Abstract

The invention discloses a method for synthesizing a C (at) SiOx / MoSe2 (at) OMWCNT material based on a silicon-molybdenum-based metal complex and application of the C (at) SiOx / MoSe2 (at) OMWCNT material. Triphenylchlorosilane and molybdenum pentachloride are dissolved in ethylene glycol, then selenium and OMWCNT are added, dispersion is conducted, and precursor dispersion liquid is obtained; and calcining the precursor dispersion liquid in an Ar atmosphere to obtain the C (at) SiOx / MoSe2 (at) OMWCNT material. The MoSe2 in the structure provides a channel for sodium ions to diffuse to SiOx, the coated carbon layer improves the conductivity of the material and relieves the problem of volume expansion in the energy storage process of the active material, meanwhile, a multi-selenium compound formed in the charging and discharging process can be prevented from being dissolved in an electrolyte, in addition, the OMWCNT also plays a supporting role and forms a conductive network, and the performance of the material is improved. When the C (at) SiOx / MoSe2 (at) OMWCNT is used as the sodium-ion battery negative electrode material, good rate capability is shown, and large-scale production can be realized.

Description

Technical Field

[0001] The present invention relates to a method for preparing a negative electrode material for a lithium-ion battery, and particularly to a method for synthesizing C@SiO x / MoSe2@OMWCNT (OMWCNT: oxidized multi-walled carbon nanotubes) materials, belonging to the field of synthesizing negative electrode materials for sodium-ion batteries. Background Art

[0002] Sodium-ion batteries (SIBs) have been widely used in solutions for the intermittent characteristics of renewable energy and energy storage applications such as electric vehicles. To further improve the energy output of SIBs, efforts have been made to study new non-insertion electrode materials with larger capacities, namely selenide negative electrodes. Molybdenum diselenide (MoSe2), as a typical transition metal sulfide, is considered an ideal negative electrode material for SIBs due to its two-dimensional layered Se-Mo-Se sandwich structure and a large number of active selenium sites. At the same time, the interlayer structure of the two-dimensional material MoSe2 can provide a channel for sodium ion diffusion. However, MoSe2 has poor semiconductor conductivity, and the volume expansion during the full discharge process leads to a rapid decay of the material capacity. Introducing carbonaceous materials is the most effective method to improve the conductivity of the entire electrode material. Currently, various MoSe2 / carbon composites have been developed and utilized, such as mesoporous carbon, biomass carbon, and carbon nanotubes. In addition, the coated carbon layer can improve the conductivity of the material while alleviating the volume expansion problem of MoSe2 during energy storage. The optimized structure generally enables MoSe2 to have good sodium storage performance. However, compared with silicon-based materials with high theoretical capacities (960 mAh g -1 ~4200 mAh g -1 ), MoSe2 theoretically provides a sodium storage specific capacity slightly higher than that of graphite (about 422 mAh g -1 ). Therefore, combining molybdenum diselenide with silicon-based materials with high specific capacities can make full use of the advantages of MoSe2 and further improve the sodium storage capacity of the composite material.

[0003] Silicon stands out due to its high theoretical capacity and becomes an ideal choice for negative electrode materials of sodium-ion batteries, and is expected to be a powerful alternative to commercially available graphite. In addition, compared with pure silicon, silicon oxide (SiO x, (0 ≤ x ≤ 2) exhibits relatively small volume changes and is easy to synthesize, etc., so it has attracted much attention and is expected to become a potential anode material for sodium-ion batteries. As an anode material for sodium-ion batteries, silicon-based materials still face some challenges, mainly due to their large volume changes and low conductivity. Current solutions mainly include alleviating the volume expansion problem by reducing the silicon particle size or compounding it with other materials, and solving the low conductivity problem by compounding it with conductive materials. Therefore, compounding silicon-based materials with MoSe2 and simultaneously coating the composite system with carbon materials to improve the performance of silicon-based materials is a good solution. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings existing in the prior art, and to propose a method for synthesizing C@SiO x / MoSe2@OMWCNT materials from a silicon-molybdenum metal complex.

[0005] To achieve the above purpose, the present invention adopts the following technical scheme:

[0006] A method for synthesizing C@SiO x / MoSe2@OMWCNT materials from a silicon-molybdenum metal complex, comprising the following steps:

[0007] S1. Dissolve triphenylchlorosilane and molybdenum pentachloride in ethylene glycol according to a molar ratio of X:1, and then add selenium and OMWCNT;

[0008] S2. Make each material evenly dispersed to obtain a precursor dispersion;

[0009] S3. Calcinate the precursor dispersion in an Ar atmosphere;

[0010] S4. Obtain C@SiO x / MoSe2@OMWCNT materials.

[0011] Further improvement, the value range of X is 1 - 4.

[0012] Further improvement, X = 3.

[0013] Further improvement, in step S1, the temperature is 20 - 30 °C.

[0014] Further improvement, in step S2, ultrasonic treatment for 2 hours is carried out to make each material evenly dispersed to obtain a precursor dispersion.

[0015] Further improvement, in step S3, the calcination temperature is 800 °C, and the calcination time is 4 - 6 h.

[0016] Further improvement: In S3, before calcination, first maintain at 60 - 100 °C for 3 - 5 h, then raise the temperature to 180 °C and still maintain for 3 - 5 h, and finally raise the temperature to the calcination temperature of 800 °C, with the calcination time being 4 - 6 h.

[0017] Further improvement: The heating rate is 4 - 6 °C / Min.

[0018] Further improvement: The masses of molybdenum pentachloride, selenium, and OMWCNT are: 27.2 : 24 : 16.

[0019] Use of a C@SiO x / MoSe2@OMWCNT material synthesized from a silicon - molybdenum - based metal complex, where the C@SiO x / MoSe2@OMWCNT material is as described above; the

[0020] C@SiO x / MoSe2@OMWCNT material is used as the anode material for sodium - ion batteries.

[0021] Beneficial technical effects brought by the technical solution of the present invention compared with the prior art:

[0022] The present invention uses triphenylchlorosilane, molybdenum pentachloride (27.3 mg (0.1 mol)), ethylene glycol, selenium, and OMWCNT as raw materials, and synthesizes

[0023] C@SiO x / MoSe2(3 - 1)@OMWCNT nanocomposites through ultrasonic dispersion and subsequent calcination. The product obtained by this method has a simpler method, lower energy consumption, higher repeatability compared with similar products. The morphology after the combination of SiO x and MoSe2 is more uniform and has more active sites. When C@SiO x / MoSe2(3 - 1)@OMWCNT is used as the anode material for sodium - ion batteries, it shows good rate performance. Specifically, at current densities of 0.1, 1.0, 5.0, and 10.0 Ag -1 , its specific capacities are 820, 574, 451, and 408 mAh g -1 . And long - cycle stability performance at a large current density of 5 Ag -1 (after 10 cycles at 0.1 Ag -1 , its discharge capacity is 836 mAh g -1 , and thereafter after 100, 1000, 5000, and 10000 cycles, its discharge capacities are maintained at 363, 307, 251, and 221 mAh g -1 ). This is conducive to realizing its large - scale production. Description of the Drawings

[0024] Figure 1 . is C@SiO x / MoSe2@OMWCNT molecular structure diagram.

[0025] Figure 2 is the reaction schematic diagram of the present invention, where (a) silicon-molybdenum metal complex, OMWCNT, (b) C@SiO x / MoSe2@OMWCNT.

[0026] Figure 3 is the mass spectrum of triphenylchlorosilane (C6H5)3SiCl) and molybdenum pentachloride (MoCl5) mixed with ethylene glycol (EG) Figure 1 .

[0027] Figure 4 is the mass spectrum of triphenylchlorosilane (C6H5)3SiCl) and molybdenum pentachloride (MoCl5) mixed with ethylene glycol (EG) Figure 2 .

[0028] Figure 5 is the mass spectrum of triphenylchlorosilane (C6H5)3SiCl) and molybdenum pentachloride (MoCl5) mixed with ethylene glycol (EG) Figure 3 .

[0029] Figure 6 is the mass spectrum of triphenylchlorosilane (C6H5)3SiCl) and molybdenum pentachloride (MoCl5) mixed with ethylene glycol (EG) Figure 4 .

[0030] Figure 7 is the mass spectrum of triphenylchlorosilane (C6H5)3SiCl) and molybdenum pentachloride (MoCl5) mixed with ethylene glycol (EG) Figure 5 .

[0031] Figure 8 is the STEM (a) image and the corresponding (b–g) EDS elemental mapping images, showing the elemental distribution of C@SiO x / MoSe2(2-1) Figure 1 .

[0032] Figure 9 is the STEM (a) image and its corresponding (b–f) EDS elemental mapping images, showing the elemental distribution of C@SiO / MoSe2(3-1)@OMWCNT Figure 2 .

[0033] Figure 10SEM (a) and TEM (b, c) images of C@MoSe2, elemental distribution electron images (d) of C@MoSe2@NMWCNT, and corresponding EDS-mapping elemental distribution diagrams (e), (f), and (g).

[0034] Figure 11 SEM images: C@SiO x / MoSe2(2-1)@OMWCNT (a, b),

[0035] C@SiO x / MoSe2(3-1)@OMWCNT (c, d), C@SiO x / MoSe2(4-1)@OMWCNT (e, f), and C@SiO x / MoSe2(5-1)@OMWCNT (g, h).

[0036] Figure 12 Images of C@SiO x / MoSe2(3-1), where (a–c) TEM images of C@SiO x / MoSe2(3-1)@OMWCNT, (d, e) HTEM images of C@SiO x / MoSe2(3-1)@OMWCNT, (f) STEM images of C@SiO x / MoSe2(3-1)@OMWCNT. (g–l)

[0037] C@SiO x Elemental distribution and elemental distribution diagrams of C@SiO

[0038] Figure 13 SEM images of C@MoSe2@OMWCNT (a), (b).

[0039] Figure 14 SEM images of C@SiO-1@OMWCNT (a)(b), C@SiO-2@OMWCNT (c)(d), and C@SiO-3@OMWCNT (e)(f).

[0040] Figure 15 Images of C@SiO x / MoSe2(1-1) (a, b), C@SiO x / MoSe2(2-1) (c, d), and C@SiO x / MoSe2(3-1) (e, f).

[0041] Figure 16TEM (a), (b) and HRTEM (c) images, STEM image and corresponding (d–i) EDS elemental distribution maps of C@MoSe2@OMWCNT.

[0042] Figure 17 HRTEM (a), TEM (b), STEM (c) images and corresponding (d-g) elemental distribution maps of C@SiO-1@OMWCNT.

[0043] Figure 18 TEM (a) and STEM (b) images and corresponding (c-f) elemental distribution maps of C@SiO-2@OMWCNT.

[0044] Figure 19 For C@SiO x / MoSe2(1-1), HRTEM (a), TEM (b) and STEM (c) images and corresponding (d-i) elemental distribution.

[0045] Figure 20 For Raman shift and XPS Figure 1 , where (a) is the XRD patterns of C@MoSe2, C@SiO x / MoSe2(1-1) and C@SiO x / MoSe2(3-1)@OMWCNT, (b–c) are the Raman shifts of C@MoSe2, OMWCNT, C@SiO x / MoSe2(1-1) and C@SiO x / MoSe2(3-1)@OMWCNT. XPS analysis of C@SiO x / MoSe2(3-1)@OMWCNT (d) and high-resolution XPS spectra (e) Si 2p, (f) O 2p, (g) Mo 2p, (h) Se 3d and (i) C 1s.

[0046] Figure 21 For Raman shift and FTIR spectra, where (a) are the Raman shifts of C@MoSe2, OMWCNTs, C@SiO / MoSe2(1-1) and C@SiO / MoSe2(3-1)@OMWCNT, (b) are the FTIR spectra of OMWCNTs, C@SiO-2@OMWCNT and C@SiO / MoSe2(3-1)@OMWCNT.

[0047] Figure 22 For TG analysis, where (a) are C@MoSe2, C@MoSe2@OMWCNT, C@SiO x / MoSe2(2-1)@OMWCNT, C@SiOx / MoSe2(3-1)@OMWCNT and C@SiO x TG analysis of / MoSe2(4-1)@OMWCNT.

[0048] Figure 23 are scanning electron microscope images, where (a)(b) C@MoSe2-Air, (c) C@MoSe2@OMWCNT-Air, and (d-i) C@SiO / MoSe2-3-1@OMWCNT-Air. C@MoSe2-Air (C@MoSe2@OMWCNT-Air, C@SiO / MoSe2-3-1@OMWCNT-Air) indicates C@MoSe2 (C@MoSe2@OMWCNT, C@SiO / MoSe2-3-1@OMWCNT) obtained by treating in an air environment at 900 °C for 4 hours.

[0049] Figure 24 are microscopic elemental distribution images, where (a-b) are transmission electron microscope images of C@MoSe2-Air, (c) is a scanning transmission electron microscope image of C@MoSe2-Air. (d, f-h) Elemental distribution and elemental mapping of the sample C@MoSe2-Air after heat treatment at 900 °C for 4 hours in an air atmosphere. The main component is molybdenum trioxide (MoO3) with 99.47%, and molybdenum trioxide wrapped by molybdenum oxycarbide (MoOC) also exists.

[0050] Figure 25 is the detection diagram of C@SiO / MoSe2(3-1)@OMWCNT-Air, where (a) is a scanning transmission electron microscope image of C@SiO / MoSe2(3-1)@OMWCNT-Air. (b, d-g) Elemental distribution and elemental distribution of each element of the sample C@SiO / MoSe2(3-1)@OMWCNT-Air after heat treatment at 900 °C for 4 hours in an air atmosphere.

[0051] Figure 26 is C@SiO x Performance diagram of / MoSe2(3-1)@OMWCNT, where (a) is C@SiO x CV curve of / MoSe2(3-1)@OMWCNT (0.1 mV s -1 ) x Galvanostatic discharge / charge voltage curve of / MoSe2(3-1)@OMWCNT (0.1 Ag -1), (c) Discharge / charge curves of C@SiOx / MoSe2@OMWCNT (0.5 Ag -1 ), (d) C@SiO x / MoSe2(3 - 1)@OMWCNT rate performance, (e)

[0052] C@SiO x / MoSe2(3 - 1)@OMWCNT long cycle (5 Ag -1 ).

[0053] Figure 27 For C@SiO x @OMWCNT, C@SiO / MoSe2 and

[0054] Charge - discharge curves of C@SiO / MoSe2(2 - 0.5)@OMWCNT (current density is 0.5 Ag -1 ). Detailed implementation manners

[0055] To make the above - mentioned features, advantages and purposes of the present invention more clearly understood, the content of the present invention will be further described in detail below in combination with specific implementation manners. Many specific details have been set forth in the above description in order to fully understand 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 improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0056] For the reaction raw materials and catalysts involved in the following examples, if not otherwise specified, they are all conventional commercially available reagents on the market.

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0058] Example 1

[0059] Construct a C@MoSe2 material. The preparation method of this composite material includes the following steps:

[0060] S1. Put Se selenium (24 mg) and MoCl5 molybdenum pentachloride (27.2 mg), and ethylene glycol (15 mL);

[0061] S2. Then perform ultrasonic treatment for 2 hours to promote the uniform dispersion of various input materials;

[0062] S3. Take out the above solution and put it into a ceramic ark, then transfer it to a tube furnace with an Ar atmosphere for calcination, and the heating rate is 4-6 °C / Min;

[0063] S4. After ultrasonic and calcination reactions, the Mo element in the precursor dispersion is in-situ selenized to MoSe2, while the organic components are in-situ converted into carbon materials, and finally a C@MoSe2 nanocomposite heterojunction material is formed.

[0064] Example 2

[0065] Construct C@SiO x / MoSe2 composite material and its lithium storage performance research. The preparation method of the composite material includes the following steps:

[0066] S1. Dissolve triphenylchlorosilane (29.4*X mg (0.1×X = 0.X mol)) and molybdenum pentachloride (27.3 mg (0.1 mol)) in ethylene glycol at a molar ratio of X:1. The other proportions mainly change the input amount of triphenylchlorosilane. The naming of the specific product is based on the 0.1 molar multiple ratio of the input amounts of triphenylchlorosilane and molybdenum pentachloride. For example: the total amount of ethylene glycol is 15 ml. Triphenylchlorosilane (29.4 mg (0.1×1 = 0.1 mol)) and molybdenum pentachloride (27.3 mg (0.1 mol)) are dissolved in ethylene glycol at a molar ratio of 1:1, and then selenium (24 mg) is added; the product is named C@SiO x / MoSe2(1-1). The other proportions change the proportion of silicon input, that is, the molar multiple ratio X-1 of the input amount of triphenylchlorosilane (X mg, (0.1×X = 0.X mol)) to molybdenum pentachloride (27.3 mg, (0.1×1 = 0.1 mol)).

[0067] S2. Then perform ultrasonic treatment for 2 hours to promote the uniform dispersion of various input materials;

[0068] S3. Take out the above solution and put it into a ceramic ark, then transfer it to a tube furnace with an Ar atmosphere for calcination, and the heating rate is 4-6 °C / Min;

[0069] S4. After ultrasonic and calcination reactions, the Si and Mo elements in the precursor dispersion are in-situ oxidized and selenized to SiO x and MoSe2, while the organic components are in-situ converted into carbon materials, and finally a C@SiO x / MoSe2(1-1) nanocomposite heterojunction material is formed.

[0070] In S1, the temperature during the addition process is room temperature, that is, 20-30 °C.

[0071] The obtained C@SiO x / MoSe2(1-1) nanocomposite heterojunction material is mixed and ground with acetylene black and sodium alginate in a mass ratio of (8:1:1), and then dispersed in a mixed solvent of water and ethanol, and then evenly coated on a copper foil to make a working electrode.

[0072] Example 3

[0073] Construct a C@MoSe2@OMWCNT composite material. The preparation method of the composite material includes the following steps:

[0074] S1. The total amount of ethylene glycol is 15 ml. Molybdenum pentachloride (27.3 mg (0.1 mol)) is dissolved in ethylene glycol, and then selenium (24 mg) and OMWCNT (16 mg) are added; the product is named C@MoSe2@OMWCNT

[0075] S2. Then, ultrasonic treatment is carried out for 2 hours to promote the uniform dispersion of various input materials;

[0076] S3. Take out the above solution and put it into a ceramic boat, and then transfer it to a tube furnace containing an Ar atmosphere for calcination, and the heating rate is 4-6 °C / Min;

[0077] S4. After ultrasonic and calcination reactions, the Mo element in the precursor dispersion is in-situ oxidized and selenized to MoSe2, while the organic components are in-situ converted into carbon materials, and finally a C@MoSe2@OMWCNT nanocomposite heterojunction material is formed.

[0078] Example 4

[0079] Construct C@SiO x @OMWCNT composite material and its lithium storage performance research. The preparation method of the composite material includes the following steps:

[0080] S1. Triphenylchlorosilane (X mg (0.1×X = 0.X mol)) is dissolved in ethylene glycol, and the other is to change the input amount of triphenylchlorosilane. The naming of specific products is based on the 0.1 molar multiple ratio of the triphenylchlorosilane feeding amount. For example: the total amount of ethylene glycol is 15 ml, and the triphenylchlorosilane (29.4 mg, (0.1×1 = 0.1 mol)) added thereto is dissolved in ethylene glycol, and then selenium (24 mg) and OMWCNT (16 mg) are added; the product is named C@SiO x-1 @OMWCNT. Other ratios are to change the input silicon ratio, that is, the multiple X of the molar amount of triphenylchlorosilane (X mg, (0.1×X = 0.X mol)) added.

[0081] S2. Then, ultrasonic treatment is carried out for 2 hours to promote the uniform dispersion of various input materials;

[0082] S3. Take out the above solution and put it into a ceramic boat, and then transfer it to a tube furnace with an Ar atmosphere for calcination at a heating rate of 4 - 6 °C / Min;

[0083] S4. After ultrasonic and calcination reactions, the Si element in the precursor dispersion is in-situ oxidized to SiO x , while the organic components are in-situ converted into carbon materials, and finally C@SiO x -1)@OMWCNT nanocomposite heterojunction materials are formed.

[0084] In S1, the temperature during the addition process is room temperature, i.e., 20 - 30 °C.

[0085] Mix the obtained C@SiO x -1@OMWCNT nanocomposite heterojunction materials with acetylene black and sodium alginate in a mass ratio of (8:1:1), grind them, disperse them in a mixed solvent of water and ethanol, and then evenly coat them on a copper foil to make a working electrode.

[0086] Example 5

[0087] Construct C@SiO x / MoSe2@OMWCNT composite materials and their lithium storage performance research. The preparation method of the composite materials includes the following steps:

[0088] S1. Dissolve triphenylchlorosilane (X mg (0.1×X = 0.X mol)) and molybdenum pentachloride (27.3 mg (0.1 mol)) in ethylene glycol at a molar ratio of X:1. The other ratios mainly change the input amount of triphenylchlorosilane. The naming of specific products is based on the 0.1 molar multiple ratio of the input amounts of triphenylchlorosilane and molybdenum pentachloride. For example: the total amount of ethylene glycol is 15 ml, and triphenylchlorosilane (88.2 mg, (0.1×3 = 0.3 mol)) and molybdenum pentachloride (27.3 mg, (0.1×1 = 0.1 mol)) are dissolved in ethylene glycol at a molar ratio of 3:1, and then selenium (24 mg) and OMWCNT (16 mg) are added; the product is named C@SiO x / MoSe2(3 - 1)@OMWCNT. Other ratios change the input ratio of silicon, that is, the molar multiple ratio X - 1 of the input amount of triphenylchlorosilane (X mg, (0.1×X = 0.X mol)) to molybdenum pentachloride (27.3 mg, (0.1×1 = 0.1 mol)).

[0089] The only special case to note is C@SiO xSynthesis of / MoSe2(2-0.5)@OMWCNT material: Triphenylchlorosilane (58.8 mg, (0.1×2 = 0.3 mol)) and molybdenum pentachloride (13.6 mg, (0.1×0.5 = 0.05 mol)) were dissolved in ethylene glycol at a molar ratio of 2:0.5, and then selenium (12 mg) and OMWCNT (16 mg) were added.

[0090] S2. Then, ultrasonic treatment was carried out for 2 hours to promote the uniform dispersion of various input materials.

[0091] S3. The above solution was taken out and placed in a ceramic boat, and then transferred to a tubular furnace containing an Ar atmosphere for calcination at a heating rate of 4 - 6 °C / Min.

[0092] S4. After ultrasonic and calcination reactions, Si and Mo elements in the precursor dispersion were in-situ oxidized and selenized to SiO x and MoSe2, respectively, while the organic components were in-situ converted into carbon materials, and finally C@SiO x / MoSe2(3-1)@OMWCNT nanocomposite heterojunction material was formed.

[0093] In S1, the temperature during the addition process was room temperature, i.e., 20 - 30 °C.

[0094] The obtained C@SiO x / MoSe2(3-1)@OMWCNT nanocomposite heterojunction material was mixed with acetylene black and sodium alginate in a mass ratio of (8:1:1), ground, and then dispersed in a mixed solvent of water and ethanol, and then evenly coated on a copper foil to make a working electrode.

[0095] Next, Examples 1 - 5 were taken as representatives for characterization:

[0096] C@MoSe2, C@SiO x / MoSe2, C@MoSe2@OMWCNT, C@SiO x @OMWCNT and C@SiO x / MoSe2@OMWCNT were characterized by SEM and TEM techniques. Figure 10 a - b show that C@MoSe2 has a flaky structure. Figure 10 The HAADF - STEM images and element distribution maps in d - g show the distribution of C, Mo, and Se in C@MoSe2. Figure 11 and Figure 12 indicate that C@SiO x / MoSe2 has a unique coating on the OMWCNT structure, which makes its morphology different from

[0097] C@MoSe2@OMWCNT( Figure 13 )、C@SiO x @OMWCNT( Figure 14 ) and C@SiO x / MoSe2( Figure 15 )。The structures of C@SiO x / MoSe2(2-1)@OMWCNT, C@SiO x / MoSe2(3-1)@OMWCNT, C@SiO x / MoSe2(4-1)@OMWCNT and C@SiO x / MoSe2(5-1)@OMWCNT are shown in Figure 11 respectively. Compared with the reference C@MoSe2@OMWCNT, the addition of silicon significantly increases the thickness of the encapsulation layer ( Figure 11 a-c), and the thickness further increases with the increase of silicon content. This increase promotes the formation of the interconnected layer between nanotubes and improves the stability of the composite. However, these morphological changes may limit the interaction between the active material and the electrolyte, which may lead to a decrease in the effective utilization rate of the active material and weaken the overall energy storage capacity of the battery. Therefore, optimizing the silicon content is crucial for improving the energy storage performance of sodium-ion batteries and maximizing the efficacy of the composite as an electrode material.

[0098] Figure 12 shows the TEM image of C@SiO x / MoSe2(3-1)@OMWCNT, revealing its complex nanostructure. The adsorption of the silicon / Mo-EG complex on OMWCNT initiates nucleation, leading to in-situ selenization and the formation of SiO x / MoSe2. Ethylene glycol (EG), as a key carbon source, helps to establish the outer carbon layer, thus forming the three-layer structure of C@SiO x / MoSe2(3-1)@OMWCNT. Compared with the TEM images of C@SiO x @OMWCNT( Figure 17 and 18 ) and C@SiO x / MoSe2( Figure 19 ), the morphology of MoSe2 on OMWCNT (C@MoSe2@OMWCNT, Figure 16 ) shows obvious characteristics. There are fewer and shorter MoSe2 sheets in the silicon matrix (C@SiO x / MoSe2(3-1)@OMWCNT, Figure 12 ), indicating that silicon restricts the growth of MoSe2 through chemical bonds. The elemental mapping shows SiO xand MoSe2 are evenly distributed. Figure 12 g-l illustrate the presence of C, O, Si, Se, and Mo in C@SiO x / MoSe2(3-1)@OMWCNT, while Figure 19 d-i focus on the element distribution in C@SiO x / MoSe2(1-1). This uniformity enhances the performance of the active material and improves the battery efficiency. In addition, the structure of C@SiO x / MoSe2(3-1)@OMWCNT aligned with the carbon nanotubes is beneficial for the movement of Na + ions.

[0099] Figure 19 a and 12d and e show that the interlayer distance of MoSe2 in the C@SiO x / MoSe2(1-1) and

[0100] C@SiO x / MoSe2(3-1)@OMWCNT structures is approximately 0.65 nm, which is consistent with the (002) plane. In addition, an increase in the interlayer distance of the C@SiO x / MoSe2(3-1)@OMWCNT configuration to approximately 0.68 nm and 0.66 nm was also observed. This increase improves the mobility of Na + ions, thus improving the electrochemical performance of the material.

[0101] XRD, Raman, and XPS analyses were performed on the characteristics of the hybrid materials. The XRD peaks of C@MoSe2, C@SiO x / MoSe2(1-1), and C@SiO x / MoSe2(3-1)@OMWCNT all correspond to MoSe2 (JCPDS 29-0914), indicating that the main component of the synthesis is MoSe2. The peak at 27.3° is the 004 crystal plane of MoSe2 ( Figure 20 a). In the Raman spectra of OMWCNT(1.0), C@MoSe2(1.02), C@SiO x / MoSe2(1-1)(1.06), and C@SiO x / MoSe2(3-1)@OMWCNT(1.05), the intensity ratios of the D peak to the G peak are basically the same, confirming that the degree of carbonization is the same and the defect states are the same after the composite OMWCNT. It can be clearly observed that 1352 cm -1 and 1586 cm -1 are the D band and G band of OMWCNT ( Figure 20 b, Figure 21 a). Among them, 238 cm -1and 283.1 cm -1 are the out-of-plane (A 1g ) and in-plane atomic vibration modes of Figure 20 c). It is worth noting that, for C@MoSe2(12.26), C@SiO x / MoSe2(1-1)(3) and C@SiO x / MoSe2(3-1)@OMWCNT(2.6), there are significant differences in the intensity ratio between (A 1g ) and , indicating that the composite OMWCNT has a significant impact on the layered structure of MoSe2 and indicating a strong interaction between MoSe2 and OMWCNT.

[0102] The surface chemical composition of

[0103] C@SiO x / MoSe2(3-1)@OMWCNT was analyzed using X-ray photoelectron spectroscopy (XPS) technology. Figure 20 Figure d shows the XPS spectrum of C@SiO x / MoSe2(3-1)@OMWCNT (including C, O, Si, Se, and Mo). For the Si 2p peak, it has been confirmed that the Si 2p spectrum of the SiO-based material can be interpreted as five oxidation states: Si 0 , Si 1+ , Si 2+ , Si 3+ , and Si 4+ , where 0, 1, 2, 3, or all 4 Si-Si bonds have been replaced by Si-O bonds. The binding energy range from Si 0 to Si 4+ is ~99.7 to ~103.8 eV ( Figure 20 Figure e). Figure 20 Figure f shows that 531.2, 533.1 eV, and 535.1 eV correspond to C=O, C-O, and O-C=O bonds, respectively. For Mo 3d, 229.1 eV and 232.2 eV are the Mo 3d 5 / 2 and 3d 3 / 2 signals (Mo +4 valence state). For Se 3d, 54.6 eV and 55.8 eV are the Se 3d 5 / 2 and Se 3d 3 / 2 signals (Se +2 valence state). For the C1s peak ( Figure 20 Figure i), 284.8 eV, 286.2 eV, and 287.8 eV correspond to C=C, C-O, and C=O bonds, respectively.

[0104] Fourier transform infrared (FTIR) spectroscopy was used to analyze OMWCNTs, C@SiO x -2@OMWCNT and C@SiO x / MoSe2(3-1)@OMWCNT samples, as shown Figure 21 below. As shown Figure 21 below, the FTIR spectrum of OMWCNT showed obvious characteristic peaks. OMWCNTs showed a broad peak at 3420 cm -1 , which originated from the stretching vibration of -OH. The peaks observed at 2900 cm -1 corresponded to the symmetric and asymmetric stretching vibrations of -CH. The sharp peak at 1730 cm -1 indicated the presence of C=O bonds. In addition, the OMWCNT spectrum showed characteristic peaks at 1630 cm -1 , representing the C=C bonds in the aromatic rings of the graphite tube walls. The shoulder peaks appearing at 1160 cm -1 and 1107 cm -1 confirmed the surface modification of OMWCNT, corresponding to C-O-C and C-O vibrations respectively. In the C@SiO x -2@OMWCNT and C@SiO x / MoSe2(3-1)@OMWCNT composites, compared with the spectrum peaks of pure OMWCNT, the overall waveform was consistent. The peaks between 900 and 1300 were significantly larger than those of pure OMWCNT, mainly due to the appearance of characteristic peaks of Si-O-Si stretching vibration (1100 cm -1 ) and Se-O (1140 cm -1 ), indicating that SiO x , SiO x / MoSe2 was successfully loaded on the surface of OMWCNT, and interactions occurred between the components, which was beneficial to improving the cycle stability during charge and discharge of the material.

[0105] The content of MoSe2 in C@MoSe2, C@MoSe2@OMWCNT, C@SiO x / MoSe2(2-1)@OMWCNT, C@SiO x / MoSe2(3-1)@OMWCNT and C@SiO x / MoSe2(4-1)@OMWCNT samples was determined by thermogravimetric analysis (TGA), as shown Figure 22As shown. For C@MoSe2 and C@MoSe2@OMWCNT, the mass of the composite material increases slightly before 350 °C, mainly due to the oxidation of MoSe2 to SeO2 and MoO3 in air, and the sublimation of SeO2 at 400 - 600 °C, the oxidation of carbon at 700 - 900 °C, and the sublimation of MoO3 when reaching 1000 °C. Surprisingly, at 1000 °C, the residues of C@MoSe2 and C@MoSe2@OMWCNT are only 3.6% and 5.3%, respectively. To clarify the nature of the remaining substances, we calcined C@MoSe2 and C@MoSe2@OMWCNT at 900 °C for four hours, and then used SEM( Figure 23 ) and TEM / STEM( Figure 24 and Figure 25 ) techniques to characterize the obtained products. The results show that mainly molybdenum oxides are wrapped by molybdenum oxycarbide (MoOC), that is, MoO3 is wrapped by the MoOC matrix, and the main substance is MoO3 (99.47%). It is expected that the formation of MoOC occurs during the carbon oxidation stage, especially in the temperature range of 400 - 600 °C.

[0106] For C@SiO x / MoSe2(2 - 1)@OMWCNT, C@SiO x / MoSe2(3 - 1)@OMWCNT and C@SiO x / MoSe2(4 - 1)@OMWCNT, during the thermogravimetric test, SiO x is completely oxidized to form SiO2, resulting in a very small mass change. The significant mass change in the system is mainly caused by the oxidation of carbon and MoSe2. This process is consistent with the previous cases of C@MoSe2 and C@MoSe2@OMWCNT. In other words, after 900 °C, the main residual substances in the system are SiO2 and MoO3 wrapped by the MoOC matrix.

[0107] According to the conservation of Mo element, the following equation (1) can be obtained:

[0108]

[0109] Wherein, and represent the average molecular weights of MoSe2 and MoO3 (400 - 600 °C), respectively, and represent the percentages of MoSe2 and MoO3 in the system, respectively. and 53.6%, 36.3%, 29.5%, 20.9% and 19.1% for C@MoSe2, C@MoSe2@OMWCNT, C@SiO / MoSe2(2-1)@OMWCNT, C@SiO / MoSe2(3-1)@OMWCNT and C@SiO / MoSe2(4-1)@OMWCNT, respectively. Therefore, the corresponding MoSe2 mass loadings are estimated to be 94.5%, 64.1%, 52%, 36.8% and 33.6%. Meanwhile, the C@SiO x / MoSe2(2-1)@OMWCNT, C@SiO x / MoSe2(3-1)@OMWCNT and C@SiO x / MoSe2(4-1)@OMWCNT contain 3.0%, 13.4% and 34.0% of SiO x , respectively.

[0110] The electrochemical performances of C@MoSe2, C@SiO x / MoSe2(2-1)@OMWCNT, C@SiO x / MoSe2(3-1)@OMWCNT and C@SiO x / MoSe2(4-1)@OMWCNT were investigated by half-cells. Figure 26 Figure a shows the cyclic voltammetry (CV) characteristics of C@SiO x / MoSe2(3-1)@OMWCNT, C@SiO x -2@OMWCNT, and C@MoSe2@OMWCNT as anodes for sodium-ion batteries. Apparently, in C@SiO x / MoSe2(3-1)@OMWCNT, five peaks (2.0, 1.0, 0.76, 0.62, and 0.28 V) appear during the discharge process in the first CV scan. The peak at 2.0 V corresponds to the formation of Na + MoSe2 with MoSe2. The peaks at 0.76 and 0.62, 0.28 V correspond to the formation of the solid electrolyte interface (SEI) layer ( x a). By comparing the curves of C@SiO Figure 26 -2@OMWCNT, the peak at 1.0 V also corresponds to the formation of the bulk electrolyte interface (SEI) layer, possibly due to the participation of SiO x in the reaction. x

[0111] In the C@SiO x / MoSe2 system, similarly, the peak at 0.5 V corresponds to the formation of the solid electrolyte interface (SEI) layer. Figure 26b shows C@SiO x / MoSe2(3-1)@OMWCNT at a constant current charge-discharge curve under 0.1Ag -1 The first discharge and charge capacities of C@SiO x / MoSe2(3-1)@OMWCNT are 1468 mAh g -1 and 685 mAh g -1 . The first energy storage efficiency is 47%, much lower than 90% - 94% of the industrial graphite anode. This is mainly attributed to C@SiO x / MoSe2(3-1)@OMWCNT. During the first charge-discharge process, when the anode potential reaches 1.0, 0.7, and 0.41 V( Figure 26 a), the electrolyte decomposes at the anode interface to form a SEI film, resulting in a lower first energy storage efficiency.

[0112] After the first cycle, the peaks at 1.43 V and 0.75 V are related to the conversion of MoSe2 to Mo and Na2Se (discharge), and the peak at 1.69 V is attributed to the oxidation of part of Na2Se to Se and part of Mo to MoSe2 (charging process)( Figure 26 a). After performing CV tests on C@SiO x @OMWCNT, it is found that the position of its peaks is mainly at 0.1 (during the charging process), which should be the sodiation process of Na x Si. This is consistent with

[0113] C@SiO x / MoSe2(3-1)@OMWCNT showing peaks near 0.1, indicating that SiO x contributes to the sodium storage capacity in the system. The CV test of the composite system C@SiO x / MoSe2(3-1)@OMWCNT mainly reflects the redox process of SiO x / MoSe2. C@SiO x / MoSe2(1-1)@OMWCNT, C@SiO x / MoSe2(2-1)@OMWCNT, C@SiO x / MoSe2(3-1)@OMWCNT, C@SiO x / MoSe2(4-1)@OMWCNT and C@SiO x / MoSe2(5-1)@OMWCNT show stable capacities of 264, 239, 428, 220, and 171 mAh g -1 after 300 cycles( Figure 26 c). Compared with other ratios, the composite system has ax When the input molar ratio of SiO to MoSe2 is 3:1, the battery performance reaches the best, and the battery cycle stability is also very good. In addition, SiO x When the input ratio of SiO to MoSe2 is 2:0.5, which is similar to 4:1, C@SiO / MoSe2(2-0.5)@OMWCNT shows attenuation after 300 cycles (6 mAh g -1 )( Figure 27 c). This is significantly worse than C@SiOx / MoSe2(4-1)@OMWCNT, indicating that MoSe2 plays a role in improving the performance of the stable material in the composite system. Without the participation of MoSe2, Figure 26 c shows that the stable capacities of C@SiO x -1@OMWCNT, C@SiO x -2@OMWCNT and C@SiO x -3@OMWCNT after 300 cycles are 171, 134 and 69 mAh g -1 ( Figure 27 a). The capacity of SiO in the system is significantly in a declining trend, and the material performance is not fully exerted. Without the participation of OMWCNT, C@SiO x / MoSe2(1-1), C@SiO x / MoSe2(2-1), and C@SiO / MoSe2(3-1) have stable capacities of 416, 376 and 86 mAh g x after 300 cycles respectively ( -1 ( Figure 27 b). With the increase of the active material, the battery performance significantly decreases, and the charge-discharge curve also significantly shows severe fluctuations, indicating that OMWCNT plays an important role in improving the cycle stability of the composite system.

[0114] Figure 26 d shows the rate performance of C@SiO x / MoSe2(3-1)@OMWCNT. At current densities of 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 , its specific capacities are 820, 710, 648, 592, 574, 542, 521, 486, 465, 451 and 408 mAh g -1 respectively. When the current density returns to 0.1 Ag -1 , the discharge capacity is 729 mAh g-1, indicating that

[0115] C@SiOx / MoSe2(3-1)@OMWCNT has good reversibility. Figure 26e shows C@SiO x / MoSe2(3-1)@OMWCNT at 5 Ag -1 long cycle performance at current density (the first 10 cycles at 0.1 Ag -1 are carried out). After 100, 500, 1000, 2500, 5000, 7500 and 10000 cycles, its discharge capacities are maintained at 363, 323, 307, 276, 251, 236 and 221 mAh g -1 , respectively, showing a stable capacity retention rate. The above battery performance comparison shows that in C@SiO with OMWCNT as the core and covered with a carbon layer x / MoSe2(3-1)@OMWCNT, under the combined action of each component of the composite system, the best sodium storage performance is shown.

[0116] The improvement of these performances is attributed to the synergistic effect between the coated carbon layer, OMWCNT, and SiO x / MoSe2. The coated carbon layer can isolate the electrolyte and improve the battery cycle performance. OMWCNT provides sites for the growth of the active material SiO x / MoSe2. At the same time, the OMWCNT network can improve the conductivity of the active material SiO x / MoSe2. The two-dimensional interlayer structure of MoSe2 provides a fast sodium ion migration channel for the system. Under the combined action of these favorable conditions, the performance of the active material is fully exerted. Therefore, each component plays an important role in improving the reversible capacity and cycle capacity of C@SiO x / MoSe2(3-1)@OMWCNT as the negative electrode of the sodium ion battery, which is a necessary condition for improving the battery performance.

[0117] In summary, SiO x / MoSe2 was synthesized by in-situ calcination of molybdenum-silicon-based organic complexes, and a three-layer structure of C@SiO x / MoSe2(3-1)@OMWCNT was prepared. Experimentally, the transmission electron microscope images showed the three-layer nano-morphology of C@SiO x / MoSe2(3-1)@OMWCNT. When

[0118] C@SiO x / MoSe2@OMWCNT is used as the negative electrode of the sodium ion battery (SIB), it shows good rate performance and cycle stability (specifically, at the current densities of 0.1, 1.0, 5.0 and 10.0 Ag -1 , its specific capacities are 820, 574, 451 and 408 mAh g -1 . And at 5 Ag -1Long cycle stability at high current density, with a discharge capacity of 836 mAh g after 10 cycles at 0.1 A g -1 After that, after 100, 1000, 5000, and 10000 cycles, the discharge capacities were maintained at 363, 307, 251, and 221 mAh g -1 respectively. Research shows that C@SiO -1 / MoSe2@OMWCNT has the ability to slow down the expansion of the active material, thus improving its structural stability as a negative electrode material for sodium-ion batteries (SIBs). The composite material can exhibit the advantages of both SiO x and MoSe2. Compared with C@SiO x / MoSe2, C@SiO x @OMWCNT, C@SiO x / MoSe2(3 - 1)@OMWCNT exhibits the best battery performance, providing a certain reference for the synthesis of high-performance battery materials. x Combined with our C@MoSe2@OMWCNT (oxidized multi-walled carbon nanotubes) synthesized based on molybdenum-based complexes, which has long cycle stability when used as a sodium storage negative electrode material, while SiO

[0119] has the characteristic of being easy to synthesize. Combining SiO x , MoSe2, and OMWCNT simultaneously for composite, that is, synthesizing x C@SiO

[0120] / MoSe2@OMWCNT is an ideal strategy ( x ). It can improve the conductivity and rate performance of the sodium-ion battery negative electrode composite while increasing the battery capacity. Specifically, MoSe2 in the structure provides a channel for sodium ions to diffuse to SiO Figure 1 , and the coated carbon layer improves the conductivity of the material and alleviates the problem of volume expansion during the energy storage process of the active material. At the same time, it can prevent the dissolution of polyselenide compounds formed during charge and discharge into the electrolyte. In addition, OMWCNT also plays a supporting role and forms a conductive network. x In this invention, C@SiO

[0121] / MoSe2@OMWCNT composite was successfully synthesized. The specific synthesis process is as x shown. That is, adsorbing molybdenum / silicon-based metal-organic compounds onto OMWCNT, and then synthesizing C@SiO Figure 2 through calcination / selenization x / MoSe2@OMWCNT. Obviously, coupling the silicon-based organic complex with the molybdenum-based metal-organic complex is the key to synthesizing the material. Specifically, we successfully coupled the two by adding triphenylchlorosilane ((C6H5)3SiCl) and molybdenum pentachloride (MoCl5) into ethylene glycol, and further verified this result by mass spectrometry (see the mass spectrum in Figures 3 - 7 ). Through STEM characterization ( Figure 8 and Figure 9 ), Figure 8 shows that in C@SiO x / MoSe2, it can be seen that SiO x grows around and co-grows with MoSe2 ( Figure 8 c–f), which indicates that coupling the silicon-based organic complex with the molybdenum-based metal-organic complex is beneficial to the formation of a co-growing morphology after calcination. This morphology is beneficial to utilizing the two-dimensional sodium ion channels of MoSe2, thereby fully releasing the energy storage performance of SiO x . Figure 9 shows that after adding OMWCNT, MoSe2 grows along the carbon network formed by OMWCNT, and at the same time SiO x grows with MoSe2 ( Figure 9 ). The results show that we successfully synthesized C@SiO x / MoSe2@OMWCNT as expected. Benefiting from the strong interaction between its carbon nanotube network, SiO x , MoSe2 and OMWCNT, as well as the sodium ion channels between the two-dimensional layers of MoSe2. When C@SiO x / MoSe2@OMWCNT is used as the anode material for sodium ion batteries, it exhibits good rate performance. Specifically, at current densities of 0.1, 1.0, 5.0, and 10.0 Ag -1 , its specific capacities are 820, 574, 451, and 408 mAh g -1 , respectively. And the long cycle stability performance at a large current density of 5 Ag -1 (after 10 cycles at 0.1 Ag -1 , its discharge capacity is 836 mAh g -1 ), and then after 100, 1000, 5000, and 10000 cycles, its discharge capacities are maintained at 363, 307, 251, and 221 mAh g -1 ). In-depth research on C@SiO x / MoSe2@OMWCNT as the anode material for sodium ion batteries provides certain reference for promoting the future development of sodium ion battery technology by combining the performance of multiple materials.

Claims

1. Synthesis of C@SiO from a silicon-molybdenum-based metal complex x / MoSe2@OMWCNT material method, characterized in that The following steps are involved: S1, dissolving triphenylsilyl chloride and molybdenum pentachloride in ethylene glycol at a molar ratio of X:1, and then adding selenium and OMWCNT; S2, making each material evenly dispersed to obtain a precursor dispersion; S3, calcining the precursor dispersion in an Ar atmosphere; S4. Obtain C@SiO x / MoSe2@OMWCNT materials.

2. Synthesis of C@SiO by the silicon-molybdenum-based metal complex as claimed in claim 1 x / MoSe2@OMWCNT material method, characterized in that The value range of X is 1-4.

3. Synthesis of C@SiO by the silicon-molybdenum-based metal complex as claimed in claim 2 x / MoSe2@OMWCNT material method, characterized in that X＝3。 4. Synthesis of C@SiO by silicon-molybdenum-based metal complex as claimed in claim 1 x / MoSe2@OMWCNT material method, characterized in that In the step S1, the temperature is 20-30°C.

5. Synthesis of C@SiO by the silicon-molybdenum-based metal complex as claimed in claim 1 x / MoSe2@OMWCNT material method, characterized in that In the step S2, ultrasonic treatment is performed for 2 hours to uniformly disperse the materials to obtain a precursor dispersion.

6. Synthesis of C@SiO by silicon-molybdenum-based metal complex as claimed in claim 1 x / MoSe2@OMWCNT material method, characterized in that In the step S3, the calcination temperature is 800° C. and the calcination time is 4 to 6 hours.

7. Synthesis of C@SiO by the silicon-molybdenum-based metal complex as claimed in claim 6 x / MoSe2@OMWCNT material method, characterized in that In S3, before calcination, the temperature is first maintained at 60-100°C for 3-5 hours, then raised to 180°C and maintained for 3-5 hours, and finally raised to a calcination temperature of 800°C for 4-6 hours.

8. Synthesis of C@SiO by silicon-molybdenum-based metal complex as claimed in claim 7 x / MoSe2@OMWCNT material method, characterized in that The heating rate is 4-6℃ / Min.

9. Synthesis of C@SiO by silicon-molybdenum-based metal complex as claimed in claim 1 x / MoSe2@OMWCNT material method, characterized in that The masses of molybdenum pentachloride, selenium and OMWCNT are: 27.2:24:

16.

10. C@SiO synthesized from a silicon-molybdenum-based metal complex x / The purpose of MoSe2@OMWCNT material is characterized by: The C@SiO x / MoSe2@OMWCNT material as described in any one of claims 1-9; the C@SiO x / MoSe2@OMWCNT material is used as anode material for sodium ion batteries.

Images