A core-shell silicon@tin selenide sulfide@carbon nanosphere structure material and preparation method thereof, lithium-ion battery silicon-based negative electrode and battery

Abstract

The present invention provides a core-shell silicon@tin selenide sulfide@carbon nanosphere structure material and its preparation method, a lithium-ion battery silicon-based negative electrode and a battery. Tin salt is used as raw material, 1,3,5-trimethylbenzene carboxylic acid is used as an organic ligand, and a solvent thermal reaction is carried out with silicon particles in an organic mixed solvent to synthesize Si@Sn-Mof; sulfur powder is used as a vulcanizing agent, argon is used as a protective gas, and high-temperature calcination is performed to generate Si@SnS2 nanocomposite materials; finally, selenium powder is used as a selenizing agent. Calcination and selenization generate a special three-dimensional core-shell Si@SnS 0.5 Se 0.5 @C nano-spherical structure material. Its special structure provides more active sites during the charge and discharge process, solving the volume expansion problem and making the battery more stable. This nano material is also safe, environmentally friendly, and inexpensive.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon negative electrode materials for lithium-ion batteries, and specifically relates to a core-shell silicon@tin selenide sulfide@carbon nanosphere structure material and a preparation method thereof, a lithium-ion battery silicon-based negative electrode and a battery. Background Art

[0002] In the rapidly developing contemporary society, due to the depletion of fossil fuels such as coal, oil, and natural gas, and their combustion also brings a series of environmental problems, clean energy such as solar energy, wind energy, hydropower, nuclear energy, and new electric energy has achieved unprecedented development.

[0003] Lithium-ion batteries (Li-ion batteries) have garnered widespread attention due to their long cycle life, high operating voltage, high energy density, and environmentally friendly properties. However, the low theoretical capacity of conventional Li-ion battery anode materials, such as graphite, has limited their development. Silicon, due to its extremely high capacity, has become one of the most promising anode materials for Li-ion batteries. However, its commercial application is limited by its large volume change during lithiation, prone to pulverization, poor cycling stability, volume expansion during charge and discharge, poor conductivity, and short cycle life.

[0004] A porous silicon-based composite negative electrode material for lithium-ion batteries, its preparation method, and its use, disclosed on November 18, 2015, discloses a capsule structure with a core made of amorphous porous silicon and a wall made of a conductive carbon material. The amorphous porous silicon has a particle size of 10 to 300 nm, a pore size of 0.5 to 100 nm, and a wall thickness of 0.5 to 10 μm. However, the preparation method for the porous silicon-based composite negative electrode material for lithium-ion batteries is complex and unsuitable for industrial scale-up. Summary of the Invention

[0005] The purpose of the present invention is to provide a core-shell silicon @ tin selenide sulfide @ carbon nanosphere structure material and its preparation method, using low-cost raw materials to prepare Si @ Sn-MOFs, and calcining with sulfur powder to obtain core-shell nanospheres Si @ SnS2, and calcining with selenium powder to obtain SnS grown on the silicon surface. 0.5 Se 0.5 Composite material Si@SnS 0.5 Se 0.5 @C. The product has a novel structure, high yield, and low cost. The preparation method is simple and suitable for industrial promotion.

[0006] Another object of the present invention is to provide a silicon-based negative electrode for lithium-ion batteries, which is prepared using the above-mentioned core-shell silicon@tin selenide sulfide@carbon nanosphere structure material, thereby improving the technical difficulties of silicon-based materials as electrode materials, such as poor cycle stability and easy volume expansion.

[0007] Another object of the present invention is to provide a lithium-ion battery prepared using the above-mentioned lithium-ion battery silicon-based negative electrode.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A method for preparing a core-shell silicon@tin selenide sulfide@carbon nanosphere structure material comprises the following steps:

[0010] 1) dispersing the silicon material in a solvent to form a uniform solution, referred to as solution A; mixing the tin salt and the organic ligand in an organic solvent and stirring them uniformly, referred to as solution B; after mixing solution A and solution B uniformly, performing a solvothermal reaction, centrifuging, washing, and drying after the reaction to obtain Si@Sn-MOFs pellets;

[0011] 2) placing the Si@Sn-MOFs pellets and sulfur powder obtained in step 1) in two magnetic boats respectively and calcining them to obtain core-shell nanospheres Si@SnS2;

[0012] 3) Mix the core-shell nanospheres Si@SnS2 obtained in step 2) with selenium powder and calcine to obtain three-dimensional core-shell Si@SnS 0.5 Se 0.5 @CNano-spherical structure material.

[0013] In step 1), the silicon material is dispersed in a solvent, and the amount ratio of the silicon material to the solvent is 0.2 to 0.8 mol / L, preferably 0.3 mol / L;

[0014] In step 1), the silicon material is silicon particles; the size of the silicon particles is 20 to 120 nm, preferably 40 to 100 nm;

[0015] In step 1), the solvent is anhydrous ethanol. Silicon is very difficult to disperse, so the present invention can be evenly dispersed in ethanol alone, and Sn-MOFs can be evenly formed on the surface of each silicon sphere. Direct addition of silicon will cause uneven silicon dispersion, so the present invention requires first dispersing the silicon material in a solvent to prepare solution A.

[0016] In step 1), the mass ratio of the tin salt to the organic ligand is 1.35:1;

[0017] In step 1), the concentration of the tin salt in the organic solvent is 0.02 to 0.2 mol·L -1 , preferably 0.04 mol·L -1 ;

[0018] In step 1), the tin salt is stannous chloride dihydrate;

[0019] In step 1), the organic ligand is 1,3,5-trichemic acid;

[0020] In step 1), the organic solvent is a mixed solvent of N,N-dimethylformamide and anhydrous ethanol, and the volume ratio of N,N-dimethylformamide to anhydrous ethanol is 4:1;

[0021] In step 1), the volume ratio of the solvent to the organic solvent is 1:5;

[0022] In step 1), the solvent thermal reaction is carried out at 120-200° C. for 10-15 hours, preferably at 150° C. for 12 hours.

[0023] In step 2), the mass ratio of Si@Sn-MOFs pellets to sulfur powder is 1:2 to 1:6, preferably 1:3;

[0024] In step 2), the calcination is carried out by mixing and calcining in a tube furnace; the calcination conditions are 450-550° C. for 3-5 hours, preferably 500° C. for 4 hours; the calcination atmosphere is Ar, which serves as a protective gas, and the purity of the Ar gas is greater than 99.99%;

[0025] In step 3), the mass ratio of the core-shell nanospheres Si@SnS2 to selenium powder is 1:1 to 1:5; preferably, the mass ratio is 1:1;

[0026] In step 3), the calcination is performed by mixing and calcining in a tube furnace at 450-550°C for 3-5 hours, preferably at 500°C for 4 hours. The atmosphere is a hydrogen-argon reducing gas, which is a 5% hydrogen and 95% argon gas by volume.

[0027] The three-dimensional core-shell Si@SnS prepared by the present invention 0.5 Se 0.5 @C nano-spherical structure material, which is grown on the surface of silicon particles, and then calcined and sulfurized in a tube furnace to sulfurize the Sn-MOFs into SnS2, and then continued to be placed in a tube furnace and converted into core-shell Si@SnS using selenium powder. 0.5 Se 0.5 @C nanocomposite material. The core-shell 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.

[0028] The present invention provides a core-shell silicon@tin selenide sulfide@carbon nanosphere structure material, which is prepared by the above method. Si is the core, SnS 0.5 Se 0.5 and C is the shell, SnS 0.5 Se 0.5In the middle layer, C is in the outermost layer, and the core-shell silicon@tin selenide sulfide@carbon nanosphere structure material size is between 50-110nm. Because the previously synthesized Sn-MOFs are a thin layer of film, like egg white, wrapped around the surface of the Si particles, the core-shell structure is finally formed. The core-shell structure helps to alleviate the volume expansion of silicon, and the small size of the silicon negative electrode material can have a larger specific surface area, thereby providing more reactive sites, which can enable the battery to achieve extremely high specific capacity. However, a very large specific surface area is also not good because it will form more SEI film.

[0029] The present invention uses SnS 0.5 Se 0.5 The reason for compounding with silicon particles is that tin has low cost, high capacity and environmental friendliness. Although the introduction of Sn can improve the conductivity and electrochemical properties of Si, the volume change of Sn may cause pulverization, side reactions and solid electrolyte interface SEI propagation, further deteriorating the contact, thereby leading to the problems of crushing and aggregation of tin-based materials and poor cycle life. In order to solve this problem, the inventors have found through a large number of experimental investigations that nano-sizing the material can greatly reduce the collapse of its structure; or combining tin with other conductive frameworks (such as carbon materials) at the nanoscale can not only buffer the volume expansion during the cycle, but also prevent nanoparticle aggregation and improve electronic conductivity. Since selenium and sulfur both have high specific capacities, and selenium-doped materials can better suppress the expansion and crushing of tin-based materials, ternary selenium sulfide has become the preferred material. And its assembly and compounding with silicon can make the composite material have good electrical conductivity. It can not only buffer the volume expansion of silicon, but also improve the dispersibility of silicon due to its high ductility, which can greatly improve the cycle life of silicon.

[0030] Although the composite material of selenium, sulfur and tin has the above advantages, there are also many difficulties that need to be overcome. For example, the first 10 cycles of the cycle are the process of repeated destruction and reconstruction of the SEI film, which leads to rapid capacity decay and difficulties such as silicon volume expansion. Therefore, the present invention adopts material nano-materialization to increase the specific surface area of ​​the material as much as possible. At the same time, the material is pre-lithiated in advance, which can also relatively reduce the loss of active materials, thereby alleviating the capacity decay. Silicon is a material with extremely stable composition. It will not change its components during high-temperature sulfidation and selenization. At the same time, the size of silicon-based materials has a great influence on battery performance. The SEI layer of large-sized nano-silicon samples is thicker than that of small-sized silicon samples, resulting in different SEI compositions. At the same time, severe side reactions and repeated growth of SEI will cause the capacity decay of nano-silicon during the cycle. Therefore, small-sized silicon negative electrode materials can affect the composition and structure of SEI, thereby inhibiting severe electrolyte decomposition and side reactions. Based on the above, the composite material synthesized by the present invention has the advantage of small size. When designing the experiment, the present invention selects small-sized silicon particles and grows a thin layer of SnS on their surface. 0.5 Se 0.5 and carbon layer, which not only maintains the small size advantage of silicon-based materials, but also alleviates the volume expansion of silicon particles.

[0031] The present invention provides a lithium-ion battery silicon-based negative electrode, which is prepared using the core-shell silicon@tin selenide sulfide@carbon nanosphere structure material.

[0032] The present invention provides a lithium-ion battery prepared using the aforementioned lithium-ion battery silicon-based negative electrode. Specifically, a core-shell silicon@tin selenide sulfide@carbon nanosphere structure material is used as the active material, mixed uniformly with conductive carbon black and PVDF in a ratio of 7.5:1.5:1 or 7:2:1, then NMP is added dropwise and magnetically stirred for 6 to 8 hours to uniformly disperse the mixture. The mixed slurry is coated on copper foil using an applicator, placed in a vacuum drying oven at 60 to 80°C, dried for 12 to 24 hours, and then pressed using a tablet press. The electrode sheets are then cut into small circular electrode sheets using a sheet cutter. The prepared electrode sheets are assembled into button cells in a glove box filled with high-purity argon and with a water and oxygen value of ≤0.01 ppm. The electrolyte comprises ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 2:6:2 as solvents. The purity of the lithium sheet is Li ≥ 99.99%, the thickness is 0.5 mm, and it is cut into the size of the electrode sheet after rolling.

[0033] Add 1 drop of electrolyte to the positive electrode shell of the battery and place the electrode sheet, then add 1 drop of electrolyte and place the diaphragm, add 2 drops of electrolyte on the diaphragm and place the lithium sheet as the counter electrode, then place two pieces of foam nickel, and add 1 drop of electrolyte, cover the negative electrode shell, press and seal the battery with a hydraulic press, and leave it for 6 to 12 hours.

[0034] Battery mechanism of the present invention:

[0035] Si+xLi + +xe - →Li x Si

[0036] SnS 0.5 Se 0.5 +xLi + +xe - →Li x SnS 0.5 Se 0.5

[0037] Li x SnS 0.5 Se 0.5 +xLi + +xe - →Li x SnSe+Li x SnS

[0038] Li x SnSe+Li x SnS+xLi + +xe - →Li x Sn+Li x Se+Li x S.

[0039] The present invention provides a three-dimensional core-shell Si@SnS 0.5 Se 0.5 In the preparation method of @C nano-spherical structure materials, tin salt is used as raw material, 1,3,5-benzenetricarboxylic acid is used as organic ligand, and a solvent thermal reaction is carried out with silicon particles in an organic mixed solvent to synthesize Si@Sn-MOFs; ethanol is selected as solvent for silicon, and the role of ethanol is to better disperse and dissolve the silicon particles. DMF+ethanol is selected as solvent for tin and organic ligands, wherein ethanol also plays a role of dissolution and dispersion, and the addition of DMF is to promote specific reactions and achieve a change in the reaction type, thereby generating MOFs. The present invention uses sulfur powder as a sulfurizing agent and argon as a protective gas, and calcines at high temperature to generate Si@SnS2 nanocomposite materials; finally, selenium powder is used as a selenizing agent, and calcined and selenized to generate a special three-dimensional core-shell Si@SnS 0.5 Se 0.5 @C nano-spherical structure material. Its special structure provides more active sites during the charge and discharge process, solving the volume expansion problem and making the battery more stable. This nano material is also safe, environmentally friendly, and inexpensive.

[0040] Compared with the prior art, the present invention has the following advantages: (1) the prepared Si@SnS 0.5 Se 0.5 @CThe application of this combination of nanocomposites in lithium-ion batteries is very novel and is the first combined application; (2) the prepared nanomaterial can well maintain the three-dimensional core-shell spherical structure and maintain the advantage of small size, can provide a large specific surface area, and can well inhibit the volume expansion of silicon; (3) the prepared nanocomposite material has stable performance, is not easy to denature in the air, and is easy to store; (4) the prepared nanocomposite material is used as a negative electrode material for lithium-ion batteries, has a large specific capacity and good cycle performance; (5) the carbon matrix shortens the path of electrons / ions and reduces the strain of volume change. Si@SnS prepared by the present invention 0.5 Se 0.5 @C composite material at 1A g -1 After 330 cycles at the same current density, the battery showed a capacity of 498 mAh g -1 The high reversible capacity, high specific capacity, stable cycle performance and robust rate performance of Si@SnS 0.5 Se 0.5 @C is an excellent and promising lithium-ion anode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the SEM image of the precursor Si@Sn-MOFs nanospheres prepared in Example 1;

[0042] Figure 2 This is the SEM image of the Si@SnS2 nanospheres prepared in Example 1;

[0043] Figure 3 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @CSEM image of nanospheres.

[0044] Figure 4 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @CTEM image of nanospheres;

[0045] Figure 5 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @C XRD pattern of nanosphere material;

[0046] Figure 6 This is the XRD pattern of the precursor Si@Sn-MOFs nanospheres prepared in Example 1;

[0047] Figure 7This is the SEM image of the Si@Sn-MOFs nanospheres prepared in Example 2;

[0048] Figure 8 This is the SEM image of the Si@SnS2 nanospheres prepared in Example 2;

[0049] Figure 9 The three-dimensional core-shell structure Si@SnS prepared in Example 2 0.5 Se 0.5 @C SEM image of nanosphere material;

[0050] Figure 10 The three-dimensional core-shell structure Si@SnS prepared in Example 2 0.5 Se 0.5 @CTEM image of nanosphere material;

[0051] Figure 11 This is the SEM image of the Si@SnS2 nanomaterial prepared in Example 3;

[0052] Figure 12 The three-dimensional core-shell structure Si@SnS prepared in Example 3 0.5 Se 0.5 @C SEM images of nanomaterials;

[0053] Figure 13 The three-dimensional core-shell structure Si@SnS prepared in Example 3 0.5 Se 0.5 @CTEM of nanomaterials;

[0054] Figure 14 The three-dimensional core-shell structure Si@SnS prepared in Example 4 0.5 Se 0.5 @C SEM images of nanomaterials;

[0055] Figure 15 The three-dimensional core-shell structure Si@SnS prepared in Example 4 0.5 Se 0.5 @CTEM image of nanomaterials;

[0056] Figure 16 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @C Rate performance test diagram of nanosphere material as negative electrode material for lithium-ion batteries;

[0057] Figure 17 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @C nanosphere materials as negative electrode materials for lithium-ion batteries at 1A g -1Charge and discharge curve test diagram under current density;

[0058] Figure 18 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @C nanosphere materials as negative electrode materials for lithium-ion batteries at 1A g -1 Cycling performance test diagram under current density;

[0059] Figure 19 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @C nanosphere material as negative electrode material for lithium-ion batteries at 0.1A g -1 Charge and discharge curve test diagram under current density;

[0060] Figure 20 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5 @C nanosphere material as negative electrode material for lithium-ion batteries at 0.1A g -1 Cycling performance test diagram under current density;

[0061] Figure 21 The pure silicon particle material of Example 5 is used as the negative electrode material of lithium ion battery at 0.1A g -1 Cycling performance test diagram under current density;

[0062] Figure 22 SnS synthesized in Example 6 0.5 Se 0.5 The material is used as anode material for lithium-ion batteries at 1A g -1 Cycling performance test diagram under current density;

[0063] Figure 23 This is the XRD pattern of the comparative material prepared in Example 7;

[0064] Figure 24 This is a diagram of the specific surface area of ​​the composite material synthesized in Example 1. DETAILED DESCRIPTION

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, 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 only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0066] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0067] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0068] Example 1

[0069] A core-shell Si@SnS 0.5 Se 0.5 The preparation method of the nanosphere structure material comprises the following steps:

[0070] 1) Preparation of precursor Si@Sn-MOFs:

[0071] Take 0.1g of 40-100nm silicon particle powder and ultrasonically disperse it in a 50mL beaker containing 12mL of anhydrous ethanol to form a uniform solution, which is recorded as solution A; weigh 0.5815g SnCl2·2H2O and 0.4280g of 1,3,5-trimethylbenzenecarboxylic acid and add them to a 100mL beaker containing a mixed solution of 12mL of anhydrous ethanol and 48mL of DMF, stir vigorously to form a uniform solution, and record it as solution B. Pour solution A into solution B and stir magnetically for 10 minutes to mix it thoroughly. Then transfer it to a polytetrafluoroethylene reactor and place it in an oven at 150℃ for 12h. Cool it naturally to room temperature, wash it with deionized water by centrifugation 4 times, wash it with ethanol twice, and vacuum dry it at 60℃ for 12h to collect the precursor Si@Sn-MOFs precipitate. Its SEM image is as shown below. Figure 1 As shown in the figure, it can be seen that it is a micro-nanosphere.

[0072] 2) Preparation of Si@SnS2:

[0073] Weigh 0.1g Si@Sn-MOFs precursor and sulfur powder in a mass ratio of 1:3 and place them in two porcelain boats respectively. The porcelain boat containing sulfur powder is placed upwind and calcined in an argon flow atmosphere at a temperature of 500°C for 4 hours. The calcination atmosphere is Ar as a protective gas with a purity of greater than 99.99%. The heating rate is 3°C / min. The precursor Si@SnS2 is collected, and its SEM image is shown below. Figure 2 As shown in the figure, it can be seen that it is a micro-nanosphere.

[0074] 3) The intermediate product Si@SnS2 was mixed with selenium powder in a mass ratio of 1:1 in a porcelain boat and calcined in a hydrogen-argon flowing atmosphere at a temperature of 500°C for 4 h. The calcination atmosphere was hydrogen-argon gas with a volume fraction of 5% hydrogen and 95% argon, and the heating rate was 2°C / min to finally obtain the product Si@SnS 0.5 Se 0.5@C, its SEM picture is as follows Figure 3 As shown in the figure, it can be seen that it is a spherical structure gathered together. Figure 4 As shown, the surface SnS 0.5 Se 0.5 And the thin film of carbon layer, Si is the core, forming a core-shell structure.

[0075] The Si@SnS obtained in this example 0.5 Se 0.5 @C composite material XRD pattern Figure 5 As shown, it is proved that the obtained product is Si@SnS 0.5 Se 0.5 @C. The XRD pattern of the Si@Sn-MOFs precursor material obtained in this embodiment is as follows Figure 6 shown.

[0076] The three-dimensional core-shell Si@SnS prepared in Example 1 0.5 Se 0.5 The active material, a nano-spherical structured material @C, was mixed with conductive carbon black and PVDF in a ratio of 7.5:1.5:1. NMP was then added dropwise and magnetically stirred for 8 hours to uniformly disperse the mixture. The resulting slurry was then coated onto copper foil using an applicator and placed in a vacuum drying oven at 60°C. After drying for 24 hours, the foil was pressed using a tablet press and then cut into small circular electrode sheets using a sheet cutter. The resulting electrode sheets were assembled into coin cells in a glove box filled with high-purity argon and containing a water and oxygen concentration of ≤0.01 ppm. The electrolyte consisted of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a 2:6:2 ratio by volume, containing 1 M LiPF6. The lithium sheets had a purity of ≥99.99% and a thickness of 0.5 mm. After rolling, they were cut to the required electrode size.

[0077] The specific method of assembling the battery is: add 1 drop of electrolyte on the positive electrode shell of the battery and place the electrode sheet, then add 1 drop of electrolyte and place the diaphragm, add 2 drops of electrolyte on the diaphragm and place the lithium sheet as the counter electrode, then place two pieces of foam nickel, add 1 drop of electrolyte, cover the negative electrode shell, press and seal the battery with a hydraulic press, and leave it for 12 hours.

[0078] Then at 0.1A g -1 、1A g -1 The cycle performance and charge-discharge performance of the button battery were tested at a current of Figure 16 、 17 , 18, 19, 20 as shown: Figure 16 The three-dimensional core-shell structure Si@SnS prepared in Example 1 0.5 Se 0.5@C Nanosphere material as a negative electrode material for lithium-ion batteries: rate performance test chart, at 0.1, 0.2, 0.5, 1.0, 1.5A g -1 The specific capacities at different current densities are 1387.9, 1309.27, 1212.77, 1084.87, and 965.41 mAh g -1 . Figure 17 Si@SnS 0.5 Se 0.5 @C nanosphere materials as negative electrode materials for lithium-ion batteries at 1A g -1 Charge and discharge curve test diagram under current density; Figure 18 Si@SnS 0.5 Se 0.5 @C nanosphere materials as negative electrode materials for lithium-ion batteries at 1A g -1 Cyclic performance test diagram under current density, which is 1A g -1 After 330 cycles at the same current density, the specific capacity is 499.1 mAh g -1 , and the Coulombic efficiency is 93.18%. Figure 19 As a negative electrode material for lithium-ion batteries at 0.1A g -1 Charge and discharge curve test diagram under current density. Figure 20 Si@SnS 0.5 Se 0.5 @C nanosphere material as negative electrode material for lithium-ion batteries at 0.1A g -1 Cyclic performance test diagram under current density, which is 0.1A g -1 After 28 cycles at a current density of 1000 mAh, the capacity is 1379.2 mAh. -1 , the coulombic efficiency is 98.82%. From the figure, we can see that there is a relatively stable charge and discharge platform and cycle performance.

[0079] Example 2

[0080] A core-shell Si@SnS 0.5 Se 0.5 The preparation method of the nanosphere structure material comprises the following steps:

[0081] 1) Preparation of precursor Si@Sn-MOFs:

[0082] Take 0.1g of silicon particle powder and ultrasonically disperse it in a 50mL beaker containing 12mL of ethanol to form a uniform solution, which is recorded as solution A. Weigh 1.35g of SnCl2·2H2O and 0.4280g of 1,3,5-trimethylbenzenecarboxylic acid and add them to a 100mL beaker containing a mixed solution of 12mL of anhydrous ethanol and 48mL of DMF, stir vigorously to form a uniform solution, and record it as solution B. Pour solution A into solution B and stir magnetically for 10 minutes to mix it thoroughly. Then transfer it to a 50mL polytetrafluoroethylene reactor and place it in an oven at 150℃ for 15h. Cool it naturally to room temperature, wash it with deionized water by centrifugation 4 times, wash it with ethanol 2 times, and vacuum dry it at 60℃ for 12h to collect the precursor Si@Sn-MOFs precipitate product. Its SEM image is as shown below. Figure 7 As shown in the figure, it can be seen that it is a nanosphere.

[0083] 2) Preparation of Si@SnS2:

[0084] Weigh 0.1g Si@Sn-MOFs precursor and sulfur powder in a mass ratio of 1:3 and place them in two porcelain boats. The porcelain boat containing sulfur powder is placed at the upwind side and calcined in an argon flowing atmosphere at a temperature of 500℃ for 4h. The calcination atmosphere is argon and the heating rate is 3℃ / min. The precursor Si@SnS2 is collected, and its SEM image is shown as follows: Figure 8 As shown in the figure, it can be seen that the micro-nanospheres and nanosheets are mixed together.

[0085] 3) The intermediate product Si@SnS2 was mixed with selenium powder in a mass ratio of 1:1 in a porcelain boat and calcined in a hydrogen-argon flowing atmosphere at a temperature of 500°C for 4 h. The calcination atmosphere was hydrogen-argon gas with a volume fraction of 5% hydrogen and 95% argon, and the heating rate was 2°C / min to finally obtain the product Si@SnS 0.5 Se 0.5 @C, its SEM picture is as follows Figure 9 As shown in the figure, it can be seen that the irregular nanospheres and nanosheets are mixed together. Figure 10 shown.

[0086] Figure 7 As can be seen, the reaction time of 15 hours for the synthesis of Si@Sn-MOFs in Example 2 is relatively long, and the high concentration of tin salts leads to thicker Sn-MOFs grown on the Si surface. The individual spheres tend to aggregate into a large mass, resulting in poor morphology. Therefore, the preferred reaction time for the present invention is 12 hours at 150°C.

[0087] Example 3

[0088] A core-shell Si@SnS 0.5 Se 0.5The preparation method of the nanosphere structure material comprises the following steps:

[0089] 1) The preparation of the precursor is the same as in Example 1;

[0090] 2) Preparation of Si@SnS2:

[0091] Weigh 0.1g Si@Sn-MOFs precursor and sulfur powder in a mass ratio of 1:6 and place them in two porcelain boats. The porcelain boat containing sulfur powder is placed at the upwind side and calcined in an argon flowing atmosphere at a temperature of 500℃ for 4h. The calcination atmosphere is argon and the heating rate is 3℃ / min. The precursor Si@SnS2 is collected, and its SEM image is shown as follows: Figure 11 As shown in the figure, it can be seen that it is a cluster of nanosheets with a size of 500nm-1μm.

[0092] 3) The intermediate product Si@SnS2 was mixed with selenium powder in a mass ratio of 1:1 in a porcelain boat and calcined in a hydrogen-argon flowing atmosphere at a temperature of 500°C for 4 h. The calcination atmosphere was hydrogen-argon gas with a volume fraction of 5% hydrogen and 95% argon, and the heating rate was 2°C / min to finally obtain the product Si@SnS 0.5 Se 0.5 @C, its SEM picture is as follows Figure 12 As shown in the figure, it can be seen that it is an irregular nanosheet structure. Figure 13 shown.

[0093] When the proportion of sulfur powder increases, the excess sulfur powder will first sublime and then condense in the tube furnace and adhere to the surface of the product to form hard lumps. The final product Si@SnS 0.5 Se 0.5 @C The surface particles are very large and numerous, which makes the surface of the sphere very rough. Figure 11 ) It can be seen that the morphology changes greatly. Figure 12 It can be seen that there are many flakes piled up on the surface, causing it to become irregular flakes. Figure 13 TEM images further confirm the irregular flakes. Compared with the examples, it can be seen that the mass ratio of Si@Sn-MOFs pellets to sulfur powder is preferably 1:3, which will synthesize the target product. A ratio exceeding 1:3 can also be synthesized, but it will affect the morphology of the composite material.

[0094] Example 4

[0095] A Si@SnS 0.5 Se 0.5 The preparation method of the composite material comprises the following steps:

[0096] 1) The preparation of the precursor is the same as in Example 1;

[0097] 2) Preparation of Si@SnS2 was the same as in Example 1;

[0098] 3) The intermediate product Si@SnS2 was mixed with selenium powder in a mass ratio of 1:5 in a porcelain boat and calcined in a hydrogen-argon flowing atmosphere at a temperature of 500°C for 4 h. The calcination atmosphere was hydrogen-argon gas with a volume fraction of 5% hydrogen and 95% argon, and the heating rate was 2°C / min to finally obtain the product Si@SnS 0.5 Se 0.5 @C, its SEM picture is as follows Figure 14 As shown in the figure, it can be seen that it is a spherical structure of varying sizes. Figure 15 As shown, the composite material can be synthesized with a selenium powder ratio between 1:1 and 1:5. However, a larger amount of selenium powder will damage the morphology. The optimal mass ratio of 1:1 for the core-shell nanospheres Si@SnS2 and selenium powder in Example 1 is 1:1.

[0099] Example 5

[0100] The battery was assembled with pure silicon particles of 40nm-100nm (the silicon particles were the same as those used in Example 1, and the process of assembling the battery was the same as that of assembling the battery with the composite material). The battery was assembled in the same manner as above and tested in the same manner and with the same parameters. Figure 21 It can be seen that pure silicon particles at 0.1A g -1 At current densities of , its cycle performance is poor and decays quickly compared with the composite material.

[0101] Example 6

[0102] The preparation was carried out in the same manner as in Example 1, except that silicon particles were not added during the preparation. SnS was synthesized separately. 0.5 Se 0.5 The nanomaterials were assembled into batteries using the same method as above and tested using the same methods and parameters. Figure 22 It can be found that it is in 1A g -1 Under these conditions, the specific capacity is low and the cycle performance is poor.

[0103] Si@SnS prepared in Example 1 0.5 Se 0.5 @C, pure silicon particles of Example 5, SnS prepared in Example 6 0.5 Se 0.5 The specific surface area of ​​the nanomaterials was tested. Before the BET test, the samples were degassed in vacuum at 120 °C for 12 h to remove the water adsorbed on the surface. Then, the physical adsorption isotherm (adsorption-desorption branch) was recorded using a specific surface area tester (ASAP Micromeritics Tristar 2460). The results were Figure 24 Si@SnS0.5 Se 0.5 The specific surface area of ​​@C is 52.93m 2 g -1 , higher than Si(39.26m 2 g -1 ), lower than SnS 0.5 Se 0.5 @C specific surface area (92.24m 2 g -1 ). Although the large specific surface area and rich porous structure can reduce the diffusion path and increase the active sites. But for silicon-based materials, too large a specific surface area will cause side reactions between the electrolyte and the silicon electrode, thereby reducing the ICE of the battery. It further proves that the synthesized Si@SnS 0.5 Se 0.5 @C nanocomposite material has excellent performance. It provides a shuttle channel for the transfer of lithium ions, thereby increasing the storage capacity of lithium ions.

[0104] Example 7

[0105] The same preparation method as in Example 1 was used except that the silicon particles were replaced with Fe3O4 balls. The Fe3O4 balls were commercially available and had a particle size of 20 nm. SnS was grown on their surface. 0.5 Se 0.5 ,from Figure 23 It can be found that nano-Fe3O4@SnS 0.5 Se 0.5 The small balls further verify the stability of the silicon particles. Even during sulfidation and selenization, the composition of the silicon particles remains unchanged, which reflects the superiority and particularity of the composite material synthesized by the present invention.

[0106] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell silicon@tin selenide sulfide@carbon nanosphere structure material, characterized in that: The preparation method comprises the following steps: 1) dispersing the silicon material in a solvent to form a uniform solution, referred to as solution A; mixing the tin salt and the organic ligand in an organic solvent and stirring them uniformly, referred to as solution B; after mixing solution A and solution B uniformly, performing a solvothermal reaction, centrifuging, washing, and drying after the reaction to obtain Si@Sn-MOFs pellets; 2) placing the Si@Sn-MOFs pellets and sulfur powder obtained in step 1) in two magnetic boats respectively and calcining them to obtain core-shell nanospheres Si@SnS2; 3) Mix the core-shell nanospheres Si@SnS2 obtained in step 2) with selenium powder and calcine to obtain three-dimensional core-shell Si@SnS 0.5 Se 0.5 @CNano-spherical structure material.

2. The preparation method according to claim 1, characterized in that In step 1), the silicon material is silicon particles; the size of the silicon particles is 40 to 100 nm.

3. The preparation method according to claim 1 or 2, characterized in that In step 1), the solvent is anhydrous ethanol.

4. The preparation method according to claim 1, characterized in that In step 1), the mass ratio of the tin salt to the organic ligand is 1-4:1; the organic ligand is 1,3,5-trimesic acid; and the organic solvent is a mixed solvent of N,N-dimethylformamide and anhydrous ethanol, and the volume ratio of N,N-dimethylformamide to anhydrous ethanol is 4:

1.

5. The preparation method according to claim 1, characterized in that In step 1), the solvent thermal reaction is carried out at 120-200° C. for 10-15 hours.

6. The preparation method according to claim 1, characterized in that In step 2), the mass ratio of Si@Sn-MOFs to sulfur powder is 1:2 to 1:6; and the calcination conditions are 450 to 550° C. for 3 to 5 hours.

7. The preparation method according to claim 1, characterized in that In step 3), the mass ratio of Si@SnS2 to selenium powder is 1:1 to 1:5; and the calcination conditions are 450 to 550° C. for 3 to 5 hours.

8. A core-shell silicon@tin selenide sulfide@carbon nanosphere structure material prepared by the preparation method according to any one of claims 1 to 7.

9. A lithium-ion battery silicon-based negative electrode, characterized in that: It is prepared using the core-shell silicon@tin selenide sulfide@carbon nanosphere structure material described in claim 8.

10. A lithium ion battery, characterized in that: It is prepared using the lithium-ion battery silicon-based negative electrode described in claim 9.

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