CN108358206B - Three-dimensional cross-linked structure silicon nano material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a three-dimensional cross-linked structure silicon nanomaterial and a preparation method and application thereof. Three-dimensional cross-linked structure silicon nanomaterials are extracted from silicate minerals by molten salt reduction method, specifically, magnesium powder or aluminum powder, aluminum chloride and silica derived from natural silicate minerals by hydrothermal acidification The precursors are mixed evenly, and a sealed molten salt reduction reaction is carried out in a reaction kettle to prepare a silicon nanomaterial with a three-dimensional cross-linked structure. The method is simple, efficient, and easy to operate, and the prepared silicon particles have the advantages of high purity, small size, and high specific capacity, and have broad application prospects in the field of energy storage such as ion battery electrode materials.

Description

A three-dimensional cross-linked structure silicon nanomaterial and its preparation method and application

technical field

The invention relates to a three-dimensional cross-linked structure silicon nanomaterial extracted and prepared from natural silicate minerals, a preparation method and application thereof, and belongs to the field of inorganic non-metallic nanomaterials.

Background technique

方法衍生而来，具有很高的合成成本和时间成本。因而，开发出一种原料丰富廉价、反应条件易得的方法来制备高性能硅负极材料具有很重要的意义。The global increase in energy demand, the massive use of non-renewable fossil fuels, and the increasingly serious environmental pollution problems have prompted researchers to explore and utilize more technologies and materials for efficient, low-cost, and environmentally friendly energy storage and conversion. In the past few years, lithium-ion batteries with better charge-discharge cycle stability have been gradually applied to practical production and life. However, the specific theoretical capacity of carbon materials, which are commercial lithium battery anode materials so far, is low (0.372Ah g ^-1 ), which is increasingly unable to meet the needs of human life. There is still a lot of room for improvement in anode materials for ion batteries. The silicon material has a very high theoretical specific capacity (about 4.20Ah g ^-1 ), but there is a serious volume expansion problem during the charge-discharge cycle, which will lead to a sharp decrease in the lithium insertion/delithiation capacity, which seriously hinders the silicon anode material. promotion and application. At the same time, the traditional magnesium thermal reaction used in the synthesis of silicon materials today requires very high temperature conditions, resulting in the formation of by-products such as magnesium-silicon alloy compounds. At the same time, high temperature conditions place high demands on the equipment required for the reduction reaction. In addition, the silica raw material used in the magnesium thermal reaction is from ethyl orthosilicate through traditional

The method is derived and has high synthetic cost and time cost. Therefore, it is of great significance to develop a method to prepare high-performance silicon anode materials with abundant and cheap raw materials and easily available reaction conditions.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simple and efficient method for extracting and preparing silicon negative electrode material from natural silicate minerals and its synthetic product and application. The silicon nanomaterial synthesized by the method has a three-dimensional cross-linked structure and excellent Lithium intercalation/delithiation performance.

A preparation method of a three-dimensional cross-linked structure silicon nanomaterial: uniformly dispersing natural silicate minerals into an acid solution for hydrothermal acidification to obtain a silica precursor; then combining the obtained silica precursor with a strong reducing agent The stable metal powder and the low melting point salt powder are mixed evenly and then transferred to the reaction kettle for the sealed molten salt reduction reaction.

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the natural silicate minerals include one or more of halloysite, silicalite, kaolinite and montmorillonite; preferably halloysite.

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the dilute acid solution used in the hydrothermal acidification treatment is hydrochloric acid or sulfuric acid.

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the natural silicate minerals are uniformly dispersed in an acid solution with a molar concentration of 0.5-10 mol/L; the preferred molar concentration of the acid solution is 2-6 mol/L; natural silicon The acid salt minerals are uniformly dispersed in the acid solution according to the solid-liquid mass/volume ratio of 1:50～100 (g/mL).

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the natural minerals are uniformly dispersed in the acid solution, and then transferred to the reaction kettle for sealing, and the temperature is raised to 80 to 150° C. The reaction is carried out for 0.5 to 10 hours; the preferred temperature range is 100 to 100 130℃, the time range is 2～5h.

In the present invention, the natural silicate minerals are uniformly dispersed in an acid solution for hydrothermal acidification to obtain a silica precursor, and the reaction product is centrifuged, washed and dried at 60° C. for 6-8 hours before being used for the subsequent molten salt reduction reaction .

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the metal powder with strong reducibility includes one or both of magnesium powder and aluminum powder; the low melting point salt powder includes aluminum chloride powder, magnesium chloride One or both of the powders.

The role of the strong reducing metal powder is to use its strong reducibility to reduce the silica in the mineral and act as a reducing agent. On the one hand, the low melting point salt acts as a reactant to participate in the reduction reaction, and on the other hand provides a reaction system for the reaction.

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the silica precursor derived from the natural silicate mineral is mixed with the metal powder with strong reducibility and the low-melting salt powder, and then transferred to the reaction kettle. Sealed, heated to 210-300°C and reacted for 2-48h; the preferred temperature range was 240-260°C, and the time range was 8-12h.

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: the mass ratio of the silica precursor obtained by the hydrothermal acidification of the natural silicate mineral to the metal powder with strong reducibility is 1:0.6-0.9, The mass ratio of the silica precursor obtained by the hydrothermal acidification of the natural silicate mineral to the low-melting point salt powder is 1:5 to 10; The mass ratio of silicon precursor to metal powder with strong reducibility is 1:0.8, and the mass ratio of silica precursor obtained by hydrothermal acidification of natural silicate minerals to low melting point salt powder is 1:8.

In the present invention, too much silica precursor derived from natural silicate minerals will lead to incomplete reaction, and high-purity nanoparticles cannot be obtained; too much metal powder will cause the reaction system to overheat and expand, and even in serious cases, there is a danger of explosion .

The preparation method of the three-dimensional cross-linked structure silicon nanomaterial: molten salt reduction reaction pickling and purification select 2-4 mol/L hydrochloric acid and 10wt% hydrofluoric acid to mix pickling with a volume ratio of 2-3:1; pickling temperature The temperature is 70-90°C, the preferred temperature is 80°C, and the pickling time is 2-6h; then it is dried at 60°C for 6-8h.

The three-dimensional cross-linked structure silicon nanomaterial is prepared by the above method. The three-dimensional cross-linked structure silicon nanomaterial is used as a negative electrode material of an ion battery.

The present invention can synthesize silicon nanomaterials with a three-dimensional cross-linked structure. Compared with the prior art, the technical solution of the present invention has the following advantages:

1. The present invention uses cheap and abundant silicate clay minerals as raw materials, and realizes the sealing reaction of acid treatment and molten salt reduction in the reaction kettle. The experimental process is simple, the equipment requirements are not high, the operation is safe, and it can be The abundant reserves of raw materials are conducive to the commercialization and application of silicon materials.

2. Using halloysite clay minerals as raw materials, magnesium powder as a reducing agent, and aluminum chloride as a molten salt system, under the conditions far lower than the traditional magnesium thermal reduction temperature (>650 ° C), such as 250 ° C, a three-dimensional Silicon nanomaterials with a cross-linked structure.

3. The present invention studies the effect of the reduction temperature on the phase of the three-dimensional cross-linked structure silicon nanomaterials, and finds that the silicon product obtained at a lower reduction temperature (such as 200° C.) has low purity and contains many impurities that are difficult to remove. See the embodiments of the present invention, comparative examples and accompanying drawings.

4. The prepared three-dimensional cross-linked silicon nanomaterials have excellent lithium battery performance when used as negative electrode active materials for lithium batteries, and can be charged and discharged for 50 cycles at constant current densities of 0.1A g ^-1 , 0.5A g ^-1 and 2A g ^-1 . The specific capacities after , 200 and 500 cycles are 2.54Ah g ^-1 , 1.87Ah g ^-1 and 0.97Ah g ^-1 , respectively, which have broad prospects in the commercial application of silicon electrode materials.

Description of drawings

Fig. 1 is the X-ray powder diffraction (XRD) pattern of the halloysite clay mineral adopted in Example 1;

Fig. ₂ is the XRD pattern of SiO obtained by hydrothermal acid treatment in Example 1;

Fig. ₃ is the energy spectrogram of the amorphous prepared SiO obtained by the hydrothermal acid treatment of Example 1;

Fig. 4 is the XRD pattern of the three-dimensional cross-linked structure silicon nanomaterial prepared in Example 1;

Fig. 5 is the SEM electron microscope inspection diagram of the three-dimensional cross-linked structure silicon nanomaterial prepared in Example 1;

Fig. 6 is the TEM electron microscope detection picture of the three-dimensional cross-linked structure silicon nanomaterial prepared in Example 1;

Figure 7 is a lithium battery performance diagram of the three-dimensional cross-linked structure silicon nanomaterial prepared in Example 1 assembled into a half-cell: (a) the capacity-voltage curve diagram of the silicon nanoelectrode material during charging and discharging; (b) the silicon nanoelectrode material Cyclic charge-discharge results at a constant current density of 0.1 A/g; (c) rate performance diagram of silicon nano-electrode materials; (d) capacity-voltage curves of silicon nano-electrode materials under different current densities during the charge-discharge process; ( e) Cyclic charge-discharge results of silicon nano-electrode materials at a constant current density of 0.5 A/g; (f) Cyclic charge-discharge results of silicon nano-electrode materials at a constant current density of 2 A/g.

Fig. 8 is the XRD pattern of the product obtained by acid treatment in Comparative Example 1;

Fig. 9 is the XRD pattern of the product prepared by Comparative Example 2;

FIG. 10 is an XRD pattern of the product prepared in Comparative Example 3. FIG.

Detailed ways

The following examples are intended to further illustrate the content of the present invention, rather than limit the protection scope of the claims of the present invention.

Example 1

Weigh 0.5 g of halloysite clay mineral and disperse it into a 2 mol/L hydrochloric acid solution (40 mL), stir evenly, transfer it to a reaction kettle, seal, and place it at 120 °C for 4 h. After the reaction product was centrifuged, washed and dried at 60°C for 6-8h, 0.2g of the product, 0.8g of magnesium powder and 8g of aluminum chloride powder were weighed and uniformly mixed, then transferred to the reaction kettle and placed at 250°C for reaction for 10h. The reaction product was purified by acid washing with a mixture of hydrochloric acid (2mol/L) and hydrofluoric acid (10wt%) at 80°C (volume ratio 2:1) for 3h, dried and dried at 60°C for 6-8h to obtain a powder sample, The prepared samples were tested for lithium battery performance. As shown in Figure 1, the halloysite clay mineral was identified as a high-purity halloysite phase by XRD; as shown in Figure 2, the powder product obtained by hydrothermal acid treatment was amorphous silica; The element type and content are analyzed and analyzed. From Figure 3, it can be seen that the elements contained in the product are silicon and oxygen, and the atomic ratio of silicon to oxygen is 1:2; as shown in Figure 4, it is reduced by magnesium powder, purified and dried. The product after that was identified as a high-purity silicon element by XRD; its morphology was analyzed by SEM and TEM, and it can be seen from Figures 5 and 6 that its morphology was a three-dimensional cross-linked nanostructure. The size of the nano-branch is about 15 nm; the lithium battery performance test is shown in Figure 7.

Example 2

Weigh 0.7 g of halloysite clay mineral and disperse it into a 5 mol/L hydrochloric acid solution (40 mL), stir evenly, transfer it to a reaction kettle, seal it, and place it at 130 °C for 2 h of reaction. After the reaction product was centrifuged, washed and dried at 60°C for 6-8h, 0.2g of the product, 0.8g of magnesium powder and 8g of aluminum chloride powder were weighed and uniformly mixed, then transferred to the reaction kettle and placed at 250°C for reaction for 10h. The reaction product was purified by acid washing with a mixture of hydrochloric acid (2mol/L) and hydrofluoric acid (10wt%) at 80°C (volume ratio 2:1) for 3h, dried and dried at 60°C for 6-8h to obtain a powder sample, The prepared sample was tested for lithium battery performance, and it was found that the performance was equivalent to that of the material prepared in Example 1.

Example 3

Weigh 0.7 g of montmorillonite and disperse it into a 2 mol/L sulfuric acid solution (40 mL), stir evenly, transfer it to a reaction kettle, seal it, and place it at 90° C. to react for 2 h. After centrifuging, washing and drying the reaction product at 60°C for 6-8 hours, weigh 0.2g of the product, 0.8g of magnesium powder, and 8g of aluminum chloride powder, mix them uniformly, and transfer them to the reaction kettle, and place them at 210°C for reaction for 4 hours. The reaction product was purified by acid washing with a mixture of hydrochloric acid (2mol/L) and hydrofluoric acid (10wt%) at 80°C (volume ratio 2:1) for 3h, dried and dried at 60°C for 6-8h to obtain a powder sample, The prepared samples were tested for lithium battery performance. It is found that the material prepared in this example is slightly inferior to the material prepared in Example 1 in terms of purity, size and performance, but can also be significantly better than the general lithium battery negative electrode active material, thus achieving the purpose of the present invention.

Comparative Example 1

Weigh 0.5 g of halloysite clay mineral and disperse it into a 2 mol/L hydrochloric acid solution (40 mL), stir evenly, transfer it to a reaction kettle, seal it, and place it at 80 °C for 4 h. After the reaction product was centrifuged, washed and dried at 60°C for 6-8 hours, a powder sample was obtained. As shown in Figure 8, the _SiO2 precursor could not be obtained at 80 °C.

Comparative Example 2

Weigh 0.5 g of halloysite clay mineral and disperse it into a 2 mol/L hydrochloric acid solution (40 mL), stir evenly, transfer it to a reaction kettle, seal it, and place it at 120 °C for reaction for 4 h. After centrifuging, washing and drying the reaction product at 60°C for 6-8 hours, 0.2g of the product, 0.8g of magnesium powder and 8g of aluminum chloride powder were weighed and uniformly mixed, then transferred to the reaction kettle and placed at 200°C for reaction for 10 hours. The reaction product was purified by acid washing with a mixture of 80°C hydrochloric acid (2mol/L) and hydrofluoric acid (10wt%) (volume ratio 2:1) for 3h, dried and dried at 60°C for 6-8h to obtain a powder sample. It can be seen from Figure 9 that the obtained silicon product is of low purity and contains many impurity phases.

Comparative Example 3

Weigh 0.5 g of halloysite clay mineral and disperse it into a 2 mol/L hydrochloric acid solution (40 mL), stir evenly, transfer it to a reaction kettle, seal, and place it at 120 °C for 4 h of reaction. After the reaction product was centrifuged, washed and dried at 60°C for 6-8h, 0.2g of the product, 0.8g of magnesium powder and 8g of aluminum chloride powder were weighed and uniformly mixed, then transferred to the reaction kettle and placed at 250°C for reaction for 10h. The reaction product was purified by acid washing with a mixture of hydrochloric acid (2mol/L) and hydrofluoric acid (10wt%) (volume ratio 2:1) at room temperature (25°C) for 3h, dried and dried at 60°C for 6-8h to obtain Powder samples. It can be seen from FIG. 10 that because the acid washing purification step is performed at a lower temperature (25° C.), the obtained silicon product has a lower purity and contains a lot of impurity phase Al ₉ Si.

Claims (12)

1. A preparation method of a three-dimensional cross-linked structure silicon nano material is characterized by comprising the following steps: uniformly dispersing halloysite into an acid solution for hydrothermal acidification treatment to obtain a silicon dioxide precursor; uniformly mixing the obtained silicon dioxide precursor, metal powder with strong reducibility and low-melting-point salt powder, transferring the mixture into a reaction kettle for sealed molten salt reduction reaction, and heating to 210-250 ℃ for reaction for 2-48 hours; acid washing, purifying and drying the reaction product to obtain the silicon nano material with the three-dimensional cross-linked structure; the metal powder with strong reducibility comprises one or two of magnesium powder and aluminum powder; the low-melting-point salt powder comprises one or two of aluminum chloride powder and magnesium chloride powder.

2. The preparation method according to claim 1, wherein the acid solution used in the hydrothermal acidification treatment is hydrochloric acid or sulfuric acid; the halloysite is uniformly dispersed into an acid solution with the molar concentration of 0.5-10 mol/L; the halloysite is uniformly dispersed in an acid solution according to the solid-liquid mass/volume ratio of 1g to 50-100 mL.

3. The method according to claim 2, wherein the molar concentration of the acid solution is 2 to 6 mol/L.

4. The preparation method according to claim 1, wherein the halloysite is uniformly dispersed in the acid solution, is transferred to a reaction kettle after being uniformly stirred, is sealed, and is heated to 80-150 ℃ for reaction for 0.5-10 h.

5. The method according to claim 4, wherein the temperature is in the range of 100 to 130 ℃ and the time is in the range of 2 to 5 hours.

6. The method according to claim 1, wherein the halloysite-derived silica precursor, the metal powder with strong reducibility and the low-melting-point salt powder are mixed uniformly, transferred to a reaction kettle, sealed, heated to 240-250 ℃ and reacted for 8-12 hours.

7. The method according to claim 1, wherein the mass ratio of the silica precursor obtained by the halloysite hydrothermal acidification treatment to the metal powder having strong reducibility is 1:0.6 to 0.9, and the mass ratio of the silica precursor obtained by the halloysite hydrothermal acidification treatment to the low-melting-point salt powder is 1:5 to 10.

8. The method according to claim 7, wherein the mass ratio of the silica precursor obtained by the hydrothermal acidification of the halloysite to the metal powder having strong reducibility is 1:0.8, and the mass ratio of the silica precursor obtained by the hydrothermal acidification of the halloysite to the powder of the low-melting-point salt is 1: 8.

9. The preparation method of claim 1, wherein the molten salt reduction reaction is performed with acid cleaning and purification by mixing 2-4 mol/L hydrochloric acid and 10 wt% hydrofluoric acid at a volume ratio of 2-3: 1; the pickling temperature is 70-90 ℃, and the pickling time is 2-6 h; and then drying for 6-8 h at 60 ℃.

10. The method according to claim 9, wherein the pickling temperature is 80 ℃.

11. A three-dimensional cross-linked silicon nanomaterial characterized by being produced by the method of any one of claims 1 to 10.

12. Use of the three-dimensionally crosslinked silicon nanomaterial of claim 11 as an ion battery negative electrode material.

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