Three-dimensional silicon, molybdenum selenide and carbon nanosphere structure material and preparation method thereof, lithium ion battery negative electrode, liquid battery and all-solid-state battery

Abstract

According to the three-dimensional silicon, molybdenum selenide and carbon nanosphere structure material and the preparation method thereof, the lithium ion battery negative electrode, the liquid battery and the all-solid-state battery provided by the invention, SiO2 spheres are subjected to magnesiothermic reduction to obtain porous silicon, the porous silicon nanoparticles are coated with MoSe2, the specific surface area is further increased by the spherical structure, and finally, a layer of thin carbon shell is coated. A conductive network formed by an internal porous structure and a spherical structure provides a rapid electron / ion transfer channel, so that electrode reaction kinetics is promoted. Meanwhile, the external carbon shell provides protection for the silicon nanoparticles, buffers the internal gaps of the material, relieves the huge volume change of the material in the Li < + > embedding / releasing process, ensures the integrity of the electrode structure, and can greatly prolong the cycle life of the battery. The method not only can be used for preparing liquid batteries, but also can be used for preparing all-solid-state batteries. And meanwhile, the all-solid-state battery effectively reduces the safety risk of a liquid battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon anode materials for lithium-ion batteries, and particularly relates to a three-dimensional silicon@molybdenum selenide@carbon nanosphere structure material and a preparation method thereof, a lithium-ion battery anode, a liquid battery, and a all-solid-state battery. Background Art

[0002] With the rapid development of electric vehicles and portable electronic devices, the demand for high-performance lithium-ion battery anodes is becoming increasingly urgent. Commercial graphite anodes can no longer meet the requirements of high-energy-density lithium-ion batteries. Silicon has received great attention due to its high theoretical specific capacity and low working potential. However, during the lithiation / delithiation process, silicon undergoes significant volume expansion (>300%), which leads to the repeated formation of the SEI film. At the same time, the electrode material quickly cracks and peels off. In addition, silicon itself exhibits poor electrical conductivity, resulting in slow ion / electron transfer rates, which seriously affects the rate performance and cycle stability of the battery. These reasons limit its practical application.

[0003] Traditional lithium-ion batteries are widely used in many fields today, but there are some obvious deficiencies. The ionic conduction efficiency of liquid electrolytes is limited to a certain extent, which is not conducive to further improving the overall charge and discharge performance of the battery and affects key indicators such as the battery life of the device.

[0004] In addition, with the continuous improvement of the requirements for battery performance and safety, all-solid-state batteries have gradually become a research hotspot. Researchers use solid electrolytes to replace liquid electrolytes to overcome the many problems brought by the above-mentioned liquid electrolytes. In terms of the anode, there is also an urgent need for high-performance anode materials to fully utilize the high safety and other characteristics of all-solid-state batteries. Among them, silicon-based anodes have great development potential, but they also need to solve problems such as silicon volume expansion and insufficient conductivity. Summary of the Invention

[0005] The purpose of the present invention is to provide a three-dimensional silicon@molybdenum selenide@carbon nanosphere structure material and a preparation method thereof, and use SiO2 spheres to obtain porous Si, and then through the hydrothermal method, and finally calcined to obtain Si@MoSe2@C composite materials through magnesiothermic reduction. The present invention provides a nanomaterial with low cost, high yield, and novel structure for the technical difficulties of silicon-based materials as electrode materials, such as easy volume expansion, poor cycle stability, and poor electrical conductivity.

[0006] Another purpose of the present invention is to provide a lithium-ion battery anode, a liquid battery, and an all-solid-state battery. Use the above three-dimensional silicon@molybdenum selenide@carbon nanosphere structure material as an active substance to prepare a lithium-ion battery anode, and then prepare a liquid battery or an all-solid-state battery.

[0007] The specific technical solution of the present invention is as follows:

[0008] A preparation method of a three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material, comprising the following steps:

[0009] 1) After mixing a selenium source hydrazine hydrate solution and a molybdenum source aqueous solution, porous silicon is added and heated for reaction;

[0010] 2) The product of step 1) and tris(hydroxymethyl)aminomethane are dispersed in water; then the pH is adjusted, and dopamine hydrochloride is continuously added for reaction;

[0011] 3) The product of step 2) is calcined in a protective atmosphere to finally obtain a Si@MoSe2@C nanocomposite.

[0012] In step 1), the molar ratio of the selenium source to the molybdenum source is 2:1; the selenium source is Se powder, and the molybdenum source is Na2MoO4·2H2O; in the selenium source hydrazine hydrate solution, the dosage ratio of the selenium source to hydrazine hydrate is 0.2 - 0.4 mol / L, preferably 0.2 mol / L; the concentration of the molybdenum source in the molybdenum source aqueous solution is 0.05 - 0.1 mol / L, preferably 0.05 mol / L; hydrazine hydrate is used as a reducing agent and a solvent, and its concentration controls the nucleation rate of molybdenum diselenide. A low concentration slows down the reaction and is conducive to the formation of small-sized particles.

[0013] In step 1), the molar ratio of the porous silicon to the selenium source is 0.5 - 3:1; preferably 0.5 - 2:1;

[0014] In step 1), the size of the porous silicon is 30 - 60 nm.

[0015] In step 1), the preparation method of the porous silicon is the magnesiothermic reduction method, specifically: SiO2 and Mg powder are mixed and ground, and then calcined in a hydrogen-argon mixed gas atmosphere; after the calcination is completed, it is soaked in an HCl solution; finally, it is alternately washed with an HCl solution and deionized water and dried to obtain porous Si spheres with a size of 30 - 60 nm. Among them, the mass ratio of SiO2 to Mg powder is 1.0 - 2.5:1; for the calcination, the heating rate is 5 °C / min, and it is calcined at 650 °C for 6 h; for the HCl solution soaking, the concentration of the HCl solution used is 1 - 5 M, and the soaking time is 3 - 10 h;

[0016] In step 1), the heating reaction is carried out in a reaction kettle, and the hydrothermal reaction is carried out at 160 - 200 °C for 10 - 20 h; preferably, the hydrothermal reaction is carried out at 200 °C for 24 h;

[0017] In step 2), the dosage ratio of tris(hydroxymethyl)aminomethane to water is 0.1 - 0.5 mol / L; water is preferably deionized water; the pH is adjusted to 8 - 9, and the pH is adjusted using a hydrochloric acid solution; the dosage ratio of dopamine hydrochloride to water is 0.006 - 0.010 mol / L;

[0018] In step 2), the dosage ratio of the product Si@MoSe2 in step 1) to water is 0.001 - 0.004 g / mL;

[0019] For the reaction described in step 2), the reaction is carried out at room temperature for 24 h;

[0020] After the reaction in step 2), collect the composite material, wash it with deionized water and ethanol, and dry it in an oven at 60 °C to obtain the product.

[0021] In step 3), the calcination means: heating up to 500 - 550 °C at a rate of 2 °C / min and calcining for 2 - 3 h; controlling the heating rate affects the pore structure of the carbon layer and improves the conductivity.

[0022] In step 3), the protective atmosphere is nitrogen.

[0023] The three-dimensional porous Si@MoSe2@C nanospherical structure material prepared by the present invention has the following process: obtaining porous Si by the thermal reduction method of SiO2 with magnesium powder, dissolving Se powder in hydrazine hydrate, then preparing a Na2MoO4·2H2O solution, mixing the two, and finally dispersing the porous silicon in the mixed solution for reaction; subsequently coating a carbon layer to convert it into a three-dimensional structured Si@MoSe2@C composite material. The porous structure can not only increase the specific surface area but also effectively alleviate the volume expansion of silicon particles, thereby improving the battery cycle stability.

[0024] In the present invention, the high specific surface area and nanopores of the porous silicon provide a confined growth space for molybdenum diselenide (MoSe2). The Si-OH groups on the silicon surface adsorb the molybdenum source through hydrogen bonding or electrostatic interaction, and then the selenium source undergoes a reduction reaction with hydrazine hydrate under heating conditions to generate MoSe2. Hydrazine hydrate serves both as a reducing agent and as a solvent to promote the release of Se 2- , control the reaction kinetics, and achieve the uniform nucleation and growth of MoSe2. In Tris buffer solution (pH 8 - 9), dopamine hydrochloride forms a highly adhesive polydopamine (PDA) coating through oxidative self-polymerization. The amino and phenolic hydroxyl groups of PDA form strong interactions with the surfaces of silicon and MoSe2 to achieve tight coating. The micropores of the porous silicon and the carbon layer form hierarchical pores, providing rich ion transport channels; and the porous silicon and the carbon layer cooperate to provide a large number of active sites to promote the rapid adsorption / desorption of lithium ions. The carbon layer coats MoSe2 and silicon to form a continuous conductive network, reducing the overall impedance and increasing the conductivity. The dopamine-derived nitrogen-doped carbon (N-C) introduces defects and active sites, further enhancing the electron transport rate. In addition, the porous structure of the porous silicon reserves expansion space to alleviate the volume expansion during lithium insertion into silicon; the carbon layer serves as a mechanical buffer layer to prevent MoSe2 and silicon from pulverizing during charge and discharge. The carbon layer can isolate silicon and MoSe2 from direct contact with the electrolyte, reduce side reactions, and improve the performance of the battery.

[0025] A three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material provided by the present invention is prepared by the above method. Porous silicon nanoparticles are coated with MoSe2, and its spherical structure is coated with a thin carbon shell. The size of the three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material is 50-100 nm, and the thickness of the carbon shell layer is 7-10 nm.

[0026] A negative electrode for a lithium-ion battery provided by the present invention is prepared by using the above three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material as an active substance.

[0027] A liquid battery provided by the present invention includes a negative electrode made of a three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material as an active substance.

[0028] The specific method for preparing the liquid battery is as follows:

[0029] After mixing the three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material with a conductive agent and a binder, a slurry is obtained by grinding, and the slurry is cast on a copper foil by film drawing and dried to be used as a negative electrode for a lithium-ion battery. A lithium sheet is used as a counter electrode, the electrolyte includes ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1:1, the electrolyte is LiPF6, and a liquid lithium-ion battery is assembled in a glove box.

[0030] In the method for preparing the liquid battery, the mass ratio of the three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material to the conductive agent and the binder is 7:2:1; the conductive agent is conductive carbon black; the binder is polyvinylidene fluoride; the film drawing is carried out on a copper foil; the drying conditions are 60-80 °C and the time is 20-24 h; finally, it is cut into small round pieces to be used as a negative electrode for a liquid lithium-ion battery.

[0031] A all-solid-state battery provided by the present invention includes a negative electrode made of a three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material as an active substance.

[0032] The preparation method of the all-solid-state lithium-ion battery is as follows: The three-dimensional silicon@molybdenum diselenide@carbon nanosphere structural material is added with a conductive agent and an electrolyte as a negative electrode, and at the same time, LPSCl electrolyte and NCM811@LiNbO3 are added, and it is pressed into a thin sheet under high pressure by a tablet press, and an all-solid-state lithium-ion battery is assembled in a glove box.

[0033] In the present invention, the three-dimensional framework structure of the porous silicon effectively alleviates the volume expansion during the lithiation / delithiation process, and the double heterojunctions between MoSe2 and the silicon and carbon layers accelerate the charge transfer through interface regulation and inhibit the electrode pulverization. Therefore, it can be used to prepare an all-solid-state battery.

[0034] In the present invention, SiO2 microspheres are magnesium thermally reduced to porous silicon, and the porous silicon nanoparticles are coated with MoSe2. Its spherical structure further increases the specific surface area, and finally a thin carbon shell is coated. The conductive network formed by the internal porous structure and spherical structure provides a fast electron / ion transfer channel, thus promoting the electrode reaction kinetics. At the same time, the external carbon shell provides protection for the silicon nanoparticles, buffers the internal voids of the material, and alleviates the large volume change of the material during the Li + insertion / extraction process, ensuring the integrity of the electrode structure and greatly improving the cycle life of the battery. The present invention nanoizes the composite material and rationally designs the spatial structure of the composite material, which can effectively increase its specific surface area and active sites.

[0035] In the present invention, by synthesizing porous silicon particles, growing MoSe2 on its surface, and finally coating a carbon layer, the capacity and cycle life of the battery are effectively improved. The present invention can be used not only for preparing liquid batteries but also for preparing all-solid-state batteries. At the same time, all-solid-state batteries effectively reduce the safety risks of liquid batteries.

[0036] Compared with the prior art, in the present invention, by the magnesium thermal reduction method, the prepared Si@MoSe2@C nanomaterial, the carbon layer can better maintain the three-dimensional porous spherical structure. At the same time, the spherical structure of MoSe2 can provide a large specific surface area and more active sites, and the porous structure can inhibit the volume expansion of silicon; making the battery have better stability. Improving the significant difference in the volume of silicon before and after Li + insertion / extraction leads to a rapid decline in capacity. In the present invention, the carbon matrix is used to shorten the electron / ion path and relieve the strain of volume change. The prepared Si@MoSe2@C nanocomposite has stable chemical properties, is not easily oxidized in air, and is easy to store; the materials prepared by the present invention can be used not only for preparing liquid batteries but also for preparing all-solid-state batteries. All-solid-state batteries have higher safety and commercial value compared with liquid batteries. Description of the Drawings

[0037] Figure 1 SEM image of the porous Si microspheres prepared in Example 1;

[0038] Figure 2 SEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 1;

[0039] Figure 3 TEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 1;

[0040] Figure 4 XRD pattern of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 1;

[0041] Figure 5 SEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 2;

[0042] Figure 6 SEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 3;

[0043] Figure 7 SEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 4;

[0044] Figure 8 SEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 5;

[0045] Figure 9 SEM image of MoSe2 prepared in Example 7;

[0046] Figure 10 SEM image of the three-dimensional porous structure Si@MoSe2@C nanospheres prepared in Example 8;

[0047] Figure 11 Charge-discharge curve of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 1 as the anode of a lithium-ion battery at a current density of 0.1 A / g; -1 ;

[0048] Figure 12 Cycling performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 1 as the anode of a lithium-ion battery at a current density of 0.1 A / g; -1 ;

[0049] Figure 13 Charge-discharge curve of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 1 as the anode of a lithium-ion battery at a current density of 0.5 A / g; -1 ;

[0050] Figure 14 Cycling performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 1 as the anode of a lithium-ion battery at a current density of 0.5 A / g; -1 ;

[0051] Figure 15 Rate performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 1 as the anode of a lithium-ion battery at a current density of 0.1 - 0.5 A / g; -1 ;

[0052] Figure 16Cycling performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 2 as the anode of a lithium-ion battery at a current density of 0.1 A g -1 ;

[0053] Figure 17 Cycling performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 3 as the anode of a lithium-ion battery at a current density of 0.1 A g -1 ;

[0054] Figure 18 Cycling performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 4 as the anode of a lithium-ion battery at a current density of 0.1 A g -1 ;

[0055] Figure 19 Cycling performance graph of the three-dimensional porous structure Si@MoSe2@C nanomaterial prepared in Example 5 as the anode of a lithium-ion battery at a current density of 0.1 A g -1 ;

[0056] Figure 20 Cycling performance graph of the Si particles purchased from Aladdin in Example 6 as the anode of a lithium-ion battery at a current density of 0.1 A g -1 ;

[0057] Figure 21 Cycling performance graph of the MoSe2 prepared in Example 7 as the anode of a lithium-ion battery at a current density of 0.1 A g -1 ;

[0058] Figure 22 Cycling performance graph of the anode of a lithium-ion battery prepared with ammonium molybdate in Example 8 at a current density of 0.1 A g -1 ;

[0059] Figure 23 Cycling performance graph of the porous Si prepared in Example 9 as the anode of a all-solid-state lithium-ion battery at a current density of 0.1 A g -1 ;

[0060] Figure 24 Cycling performance graph of the MoSe2 prepared in Example 10 as the anode of a all-solid-state lithium-ion battery at a current density of 0.1 A g -1 ;

[0061] Figure 25 Charge-discharge curve of the Si@MoSe2@C prepared in Example 11 as the anode of a all-solid-state lithium-ion battery at a current density of 0.1 A g-1;

[0062] Figure 26The rate performance graph of the Si@MoSe2@C prepared in Example 11 as the anode of a all-solid-state lithium-ion battery at a current density of 0.1-0.5 A g -1 ;

[0063] Figure 27 The cycle performance graph of the Si@MoSe2@C prepared in Example 11 as the anode of a all-solid-state lithium-ion battery at a current density of 0.1 A g -1 ; Detailed implementation manners

[0064] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0065] The test materials and reagents used in the following embodiments, unless otherwise specified, can all be obtained from commercial channels.

[0066] For those embodiments where specific technologies or conditions are not indicated, they can all be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0067] Example 1

[0068] A preparation method of a three-dimensional Si@MoSe2@C nanosphere structure material, comprising the following steps:

[0069] 1) Preparation of porous Si microspheres:

[0070] The SiO2 microspheres are reduced by the thermal reduction method of magnesium powder, specifically: 0.1 g of SiO2 and 0.1 g of Mg powder are mixed and ground for 10 min, and then placed in a hydrogen-argon mixed gas atmosphere (the volume ratio of hydrogen is 5%), and the temperature is raised at a rate of 5 °C / min to 650 °C and calcined for 6 h. After the calcination is completed, the sample is soaked in 1 M HCl solution for 5 h, and finally washed alternately with HCl solution and deionized water 3 times, and the sample is dried in an oven at 60 °C to obtain porous Si microspheres. Its SEM image is as Figure 1 shown. It can be seen from the figure that it has a porous structure with a size of 30-60 nm.

[0071] 2) Preparation of porous Si@MoSe2@C:

[0072] Under magnetic stirring, 0.158 g of Se powder was dissolved in 10 mL of hydrazine hydrate. Then, 0.242 g of Na2MoO4·2H2O was dissolved in 20 mL of deionized water, and the solution was obtained by ultrasonic treatment for 15 min. The selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution. Finally, 0.1 g of porous silicon was dispersed in the mixed solution, and hydrothermal reaction was carried out at 200 °C for 24 h. 0.1 g of the prepared product was taken and dispersed in 50 mL of deionized water, and ultrasonic treatment was carried out for 10 min. Under magnetic stirring, 1.21 g of tris(hydroxymethyl)aminomethane was added to the solution. Then, the pH was adjusted to 8.5 with hydrochloric acid solution, and 60 mg of dopamine hydrochloride was further added, and the reaction was carried out at room temperature for 24 h. The composite material was collected and washed repeatedly with deionized water and ethanol, and the sample was dried in an oven at 60 °C. The dried nanomaterial was heated to 500 °C at a heating rate of 2 °C / min and calcined in a nitrogen atmosphere for 3 h, and finally a three-dimensional Si@MoSe2@C nanosphere structure material was obtained. Its SEM image is as shown in Figure 2 shown. It can be seen from the figure that it is a spherical structure aggregated together. The TEM image is as shown in Figure 3 shown.

[0073] The XRD pattern of the Si@MoSe2@C composite material obtained in this example is as shown in Figure 4 shown. The standard cards from top to bottom in the figure are Si, C, and MoSe2 in turn, proving that the obtained product is Si@MoSe2@C.

[0074] Example 2

[0075] A preparation method of a three-dimensional Si@MoSe2@C nanosphere structure material, comprising the following steps:

[0076] 1) The preparation of porous Si is the same as that in Example 1;

[0077] 2) The preparation of porous Si@MoSe2@C:

[0078] Under magnetic stirring, 0.316 g of Se powder was dissolved in 10 mL of hydrazine hydrate, and then 0.484 g of Na2MoO4·2H2O was dissolved in 20 mL of deionized water. The solution was obtained by ultrasonic treatment for 15 min. The selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution. Finally, 0.1 g of porous silicon was dispersed in the mixed solution, and hydrothermal reaction was carried out at 200 °C for 24 h. 0.1 g of the prepared product was taken and dispersed in 50 mL of deionized water, and ultrasonic treatment was carried out for 10 min. Under magnetic stirring, 1.21 g of tris(hydroxymethyl)aminomethane was added to the solution. Then, the pH was adjusted to 8.5 with hydrochloric acid solution, and 60 mg of dopamine hydrochloride was continuously added, and the reaction was carried out at room temperature for 24 h. The composite material was collected and washed repeatedly with deionized water and ethanol, and the sample was dried in an oven at 60 °C. The dried nanomaterial was heated to 500 °C at a heating rate of 2 °C / min and calcined in a nitrogen atmosphere for 3 h, and finally porous Si@MoSe2@C was obtained. Its SEM image is as shown in Figure 5 shown. It can be seen from the figure that it is a spherical structure aggregated together.

[0079] Example 3 (for comparison)

[0080] A preparation method of a three-dimensional Si@MoSe2@C nanosphere structure material, comprising the following steps:

[0081] 1) The preparation of porous Si is the same as that in Example 1;

[0082] 2) The preparation of porous Si@MoSe2@C:

[0083] Under magnetic stirring, 0.158 g of Se powder was dissolved in 10 mL of hydrazine hydrate, and then 0.242 g of Na2MoO4·2H2O was dissolved in 20 mL of deionized water. The solution was obtained by ultrasonic treatment for 15 min. The selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution. Finally, 0.1 g of porous silicon was dispersed in the mixed solution, and hydrothermal reaction was carried out at 150 °C for 18 h. 0.1 g of the prepared product was taken and dispersed in 50 mL of deionized water, and ultrasonic treatment was carried out for 10 min. Under magnetic stirring, 1.21 g of tris(hydroxymethyl)aminomethane was added to the solution. Then, the pH was adjusted to 8.5 with hydrochloric acid solution, and 60 mg of dopamine hydrochloride was continuously added, and the reaction was carried out at room temperature for 24 h. The composite material was collected and washed repeatedly with deionized water and ethanol, and the sample was dried in an oven at 60 °C. The dried nanomaterial was heated to 500 °C at a heating rate of 2 °C / min and calcined in a nitrogen atmosphere for 3 h, and finally porous Si@MoSe2@C was obtained. Its SEM image is as shown in Figure 6 shown. It can be seen from the figure that it is a spherical structure aggregated together.

[0084] Example 4 (for comparison)

[0085] A method for preparing a three-dimensional Si@MoSe2@C nanosphere structure material comprises the following steps:

[0086] 1) Preparation of porous Si is the same as in Example 1;

[0087] 2) Preparation of porous Si@MoSe2@C:

[0088] Under magnetic stirring, 0.079g Se powder was dissolved in 10mL hydrazine hydrate, and then 0.121g Na2MoO4·2H2O was prepared and dissolved in 20mL deionized water. The solution was obtained by ultrasonication for 15min, and the selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution. Finally, 0.1g porous silicon was dispersed in the mixed solution and hydrothermally reacted at 200℃ for 24h; 0.1g of the prepared product was taken and dispersed in 50mL deionized water and ultrasonicated for 10min; under magnetic stirring, 1.21g tris(hydroxymethyl)aminomethane) was added to the solution; then the pH was adjusted to 8.5 with hydrochloric acid solution, and 60mg dopamine hydrochloride was added, and the reaction was carried out at room temperature for 24h. The composite material was collected and washed with deionized water and ethanol several times, and the sample was dried in an oven at 60℃. The dried nanomaterial was heated to 500℃ at a heating rate of 2℃ / min, calcined in a nitrogen atmosphere for 3h, and finally porous Si@MoSe2@C was obtained. Its SEM picture is as follows Figure 7 As shown, it can be seen from the figure that it is a spherical structure gathered together.

[0089] Example 5 (for comparison)

[0090] A method for preparing a three-dimensional Si@MoSe2@C nanosphere structure material comprises the following steps:

[0091] Under magnetic stirring, 0.158g Se powder was dissolved in 10mL hydrazine hydrate, and then 0.242g Na2MoO4·2H2O was prepared and dissolved in 20mL deionized water, and ultrasonicated for 15min to obtain a solution, and the selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution, and finally 0.1g Si beads (size 30-60nm) purchased from Aladdin were dispersed in the mixed solution, and hydrothermally reacted at 200℃ for 24h; 0.1g of the prepared product was dispersed in 50mL deionized water, and ultrasonicated for 10min; under magnetic stirring, 1.21g tris(hydroxymethyl)aminomethane was added to the solution; then the pH was adjusted to 8.5 with hydrochloric acid solution, and 60mg dopamine hydrochloride was added, and the reaction was carried out at room temperature for 24h. The composite material was collected, washed with deionized water and ethanol for many times, and the sample was dried in an oven at 60℃. The dried nanomaterials were heated to 500°C at a heating rate of 2°C / min and calcined in a nitrogen atmosphere for 3 hours to obtain porous Si@MoSe2@C. Figure 8 As shown, it can be seen from the figure that it is a spherical structure gathered together.

[0092] Example 6 (for comparison)

[0093] A method for preparing porous Si, comprising the following steps:

[0094] The preparation of porous Si was the same as in Example 1; 0.1 g of porous silicon was taken for comparative experiments, and a liquid battery was assembled to test the electrochemical performance.

[0095] Example 7 (for comparison)

[0096] A method for preparing MoSe2, comprising the following steps:

[0097] Under magnetic stirring, 0.158 g of Se powder was dissolved in 10 mL of hydrazine hydrate, and then 0.242 g of Na2MoO4·2H2O was dissolved in 20 mL of deionized water. The solution was obtained by ultrasonic treatment for 15 min. The selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution, and finally hydrothermal reaction was carried out at 200 °C for 24 h; its SEM image is as Figure 9 shown.

[0098] 0.1 g of the product was taken for comparative experiments, and a liquid battery was assembled to test the electrochemical performance

[0099] Example 8 (for comparison)

[0100] A method for preparing Si@MoSe2@C nanomaterials, comprising the following steps:

[0101] 1) The preparation of porous Si was the same as in Example 1;

[0102] 2) The preparation of porous Si@MoSe2@C:

[0103] Under magnetic stirring, 0.158 g of Se powder was dissolved in 10 mL of hydrazine hydrate, and then 0.242 g of (NH4)2MoO4·2H2O was dissolved in 20 mL of deionized water. The solution was obtained by ultrasonic treatment for 15 min. The selenium source hydrazine hydrate solution was mixed with the molybdenum source aqueous solution, and finally 0.1 g of porous silicon was dispersed in the mixed solution, and hydrothermal reaction was carried out at 200 °C for 24 h; 0.1 g of the prepared product was taken and dispersed in 50 mL of deionized water, and ultrasonic treatment was carried out for 10 min; under magnetic stirring, 1.21 g of tris(hydroxymethyl)aminomethane was added to the solution; then the pH was adjusted to 8.5 with hydrochloric acid solution, and 60 mg of dopamine hydrochloride was further added, and the reaction was carried out for 24 h. The composite material was collected and washed with deionized water and ethanol for many times, and the sample was dried in an oven at 60 °C. The dried nanomaterials were heated to 500 °C at a heating rate of 2 °C / min, and calcined in a nitrogen atmosphere for 3 h, and finally the product was obtained.

[0104] Its SEM image is as Figure 10As shown, it can be seen from the figure that the expected spherical structure fails to be synthesized. This indicates that after changing to ammonium molybdate, due to the by-products of the decomposition of NH 4+ and the lack of structure-directing ability, it is difficult to achieve a synergistic effect. The template effect of sodium ions promotes the formation of porous silicon; the absence of nitrogen residues avoids impurity interference with the crystallization of MoSe2; the controllable thermal decomposition path optimizes the pore structure and the component interface. NH 4+ decomposition will produce NH3, resulting in uneven pore structure, and the remaining N may block the pores, reducing the specific surface area and ion transport efficiency; while Na + will not. In the present invention, Na2MoO4·2H2O is used.

[0105] Example 9 (for comparison)

[0106] A full-solid-state lithium-ion battery made of porous Si includes the following steps:

[0107] The porous Si synthesis step is the same as that in Example 6, and a full-solid-state lithium-ion battery is assembled in a glove box.

[0108] Example 10 (for comparison)

[0109] A full-solid-state lithium-ion battery made of MoSe2 includes the following steps:

[0110] The MoSe2 synthesis step is the same as that in Example 7, and a full-solid-state lithium-ion battery is assembled in a glove box.

[0111] Example 11

[0112] A full-solid-state lithium-ion battery made of a three-dimensional Si@MoSe2@C nanosphere structure material includes the following steps:

[0113] A full-solid-state lithium-ion battery is assembled in a glove box: The three-dimensional porous Si@MoSe2@C composite material obtained in Example 1 is added with a conductive agent and an electrolyte and mixed as the negative electrode. At the same time, LPSCl electrolyte and NCM811@LiNbO3 are added and pressed into a thin sheet under high pressure by a tablet press, and a full-solid-state lithium-ion battery is assembled in a glove box. Among them, the material dosage: 10 mg of Si@MoSe2@C composite material + 5 mg of conductive carbon black + 20 mg of LPSCl electrolyte; 70 mg of LPSCl electrolyte; 10 mg of NCM811@LiNbO3.

[0114] The preparation methods of the solid batteries in Example 9 and Example 10 are carried out according to the above method in Example 11.

[0115] In addition, the three-dimensional Si@MoSe2@C nanosphere structure material obtained in Example 1 is used to prepare a liquid battery:

[0116] The mass ratio of the three-dimensional Si@MoSe2@C nanosphere structural material obtained in Example 1, conductive carbon black, and polyvinylidene fluoride is 7:2:1; the film is cast on a copper foil; the drying conditions are 80 °C for 20 h; finally, it is cut into small round pieces. As the negative electrode of a liquid lithium-ion battery, a lithium sheet is used as the counter electrode, the electrolyte is ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1:1, and the electrolyte is LiPF6 (1 mol L -1 ), and a liquid lithium-ion battery is assembled in a glove box.

[0117] The charge-discharge performance of the assembled lithium-ion battery was tested using a Neware battery tester. The cyclic stability test results at different current densities are as Figures 11 to 15 shown ( Figures 11 - 15 is the performance test of the liquid lithium-ion battery prepared in Example 1). After 100 cycles at a current density of 0.1 Ag -1 , the discharge specific capacity of the battery is 759 mAh g -1 , and the average charge-discharge efficiency remains above 99%; after 100 cycles at a current density of 0.5 Ag -1 , the discharge specific capacity of the battery is 429 mAh g -1 , and the Coulomb efficiency remains at about 100%. When the current density changes from 0.1 to 0.5 Ag -1 , and then returns to 0.1 Ag -1 , the discharge specific capacity of the battery is still 510 mAh g -1 , indicating its good reversibility.

[0118] Figures 16 to 22 are the cyclic performance diagrams of the lithium-ion batteries corresponding to the composite materials prepared in Examples 2-8 as the negative electrode. At a current density of 0.1 Ag -1 , after 50 cycles of the lithium-ion batteries assembled with the composite materials synthesized in different examples, the discharge specific capacities are 624, 513, 531, 581, 400, 211, and 71 mAh g -1 .

[0119] In Examples 3 and 4 (as comparative data), due to the too low reaction concentration of the selenium source and molybdenum source, the crystallinity of the product is poor, and the MoSe2 intermediate layer cannot be formed. And too low temperature will lead to poor crystallinity and decreased performance.

[0120] Figures 23 to 27 is the performance diagram of the all-solid-state battery. The performances of Examples 9-11 are 36.3, 37.8, and 61.9 mAh g -1 respectively. Example 11 also shows good rate performance in Figure 26 .

[0121] In the present invention, porous Si is first obtained by the thermal reduction method of magnesium powder using SiO2, and finally a carbon layer is coated to obtain a Si@MoSe2@C composite material with a three-dimensional structure. The porous silicon nanoparticles are combined with MoSe2, and the layered structure of MoSe2 effectively provides a fast diffusion electron transfer channel, thereby promoting the electrode reaction kinetics. The outermost layer is coated with a thin carbon shell, which alleviates the volume expansion of silicon and at the same time plays a supporting role to ensure the stability of the composite material, thus significantly improving the cycle stability of the battery. This material is applied to the negative electrode of liquid and all-solid-state lithium-ion batteries. Compared with pure Si and MoSe2 lithium-ion batteries, it has good cycle performance and rate performance.

[0122] The description of the above embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of a three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material, characterized in that, The preparation method includes the following steps: 1) After mixing the selenium source hydrazine hydrate solution with the molybdenum source aqueous solution, porous silicon is added and heated for reaction; 2) The product of step 1) and tris(hydroxymethyl)aminomethane are dispersed in water; then the pH is adjusted, and dopamine hydrochloride is continuously added for reaction; 3) The product of step 2) is calcined in a protective atmosphere to finally obtain the Si@MoSe2@C nanocomposite.

2. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of the porous silicon to the selenium source is 0.5 - 3:

1.

3. The preparation method according to claim 1, wherein In step 1), the molybdenum source is Na2MoO4·2H2O.

4. The preparation method according to claim 1 or 2, characterized in that, In step 1), the molar ratio of the porous silicon to the selenium source is 0.5 - 3:

1.

5. The preparation method according to claim 1 or 2, characterized in that, In step 1), the heating reaction is carried out in a reaction kettle, and hydrothermal reaction is carried out at 160 - 200 °C for 10 - 20 h.

6. The preparation method according to claim 1 or 2, characterized in that, In step 3), the calcination means: heating to 500 - 550 °C at a rate of 2 °C / min and calcining for 2 - 3 h.

7. A three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material is prepared by using the preparation method described in any one of claims 1 - 6. In the three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material, porous silicon nanoparticles wrap MoSe2, and its spherical structure is coated with a thin carbon shell; the size of the three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material is 50 - 100 nm, and the thickness of the carbon shell layer is 7 - 10 nm.

8. A negative electrode of a lithium-ion battery is prepared by using the three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material described in claim 7 as an active substance.

9. A liquid battery includes a negative electrode made of the three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material described in claim 7 as an active substance.

10. A all-solid-state battery includes a negative electrode made of the three-dimensional silicon@molybdenum selenide@carbon nanosphere structural material described in claim 7 as an active substance.

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