阅读说明：本技术 氧化钛包覆多孔中空硅球、其制备方法及其应用 (Titanium oxide coated porous hollow silicon ball, preparation method and application thereof ) 是由 白岩 关玉明 赵晓磊 游志江 于 2020-12-01 设计创作，主要内容包括：本发明提供了一种氧化钛包覆多孔中空硅球、其制备方法及其应用。上述制备方法包括以下步骤：S1,采用溶胶-凝胶法制备含有模板剂的空心二氧化硅球；S2,将空心SiO-2球进行镁热还原,得到含有模板剂的空心硅球；S3,在空心硅球的表面包覆TiO-(2-x),其中x为0～0.6,得到TiO-(2-x)包覆的空心硅球；S4,煅烧TiO-(2-x)包覆的空心硅球,得到氧化钛包覆多孔中空硅球。通过本发明方法制备得到的氧化钛包覆多孔中空硅球很好地改善了空心硅球导电性差、循环过程中体积变化大的问题,具有良好的点循环性能,非常适合作为锂离子电池负极材料使用。(The invention provides a titanium oxide coated porous hollow silicon ball, a preparation method and application thereof. The preparation method comprises the following steps: s1, preparing hollow silica spheres containing the template agent by adopting a sol-gel method; s2, mixing the hollow SiO 2 Carrying out magnesiothermic reduction on the spheres to obtain hollow silicon spheres containing the template agent; s3, wrapping the surface of the hollow silicon ballCoated with TiO 2‑x Wherein x is 0-0.6, to obtain TiO 2‑x A coated hollow silicon sphere; s4, calcining TiO 2‑x And coating the hollow silicon spheres to obtain the titanium oxide coated porous hollow silicon spheres. The titanium oxide coated porous hollow silicon spheres prepared by the method well solve the problems of poor conductivity and large volume change in the circulating process of the hollow silicon spheres, have good point circulation performance, and are very suitable for being used as the negative electrode material of a lithium ion battery.)

1. The preparation method of the titanium oxide coated porous hollow silicon spheres is characterized by comprising the following steps:

s1, preparing hollow silica spheres containing the template agent by adopting a sol-gel method;

s2, mixing the hollow SiO₂Carrying out magnesiothermic reduction on the spheres to obtain hollow silicon spheres containing the template;

s3, coating TiO on the surface of the hollow silicon ball_2-xWherein x is 0-0.6, to obtain TiO_2-xA coated hollow silicon sphere;

s4, calcining TiO_2-xAnd coating the hollow silicon spheres to obtain the titanium oxide coated porous hollow silicon spheres.

2. The method for preparing a composite material according to claim 1, wherein the step S1 includes:

dissolving ammonia water and the template agent in a first reaction solvent to form a pre-reaction system;

adding tetraethoxysilane into the pre-reaction system to carry out a first precipitation reaction to obtain a first product system;

and aging and centrifugally separating the first product system to obtain the hollow silica spheres containing the template agent.

3. The method of claim 2, wherein the template agent is cetyltrimethylammonium bromide; preferably, the volume ratio of ammonia water to the tetraethoxysilane is 1: 1-1: 2, 0.15-0.2 g of the template agent is used for each milliliter of ammonia water, and the mass concentration of the ammonia water is 28-35%.

4. The preparation method according to claim 2 or 3, wherein the temperature of the first precipitation reaction is 30-50 ℃, and the time of the first precipitation reaction is 24-36 h; preferably, the first reaction solvent is a mixed solvent of ethanol and deionized water; preferably, the aging temperature in the aging step is 90-95 ℃.

5. The production method according to any one of claims 1 to 4, wherein the step S2 includes:

mixing the hollow silica spheres, magnesium powder and sodium chloride to obtain mixed powder;

placing the mixed powder in an inert environment for reduction reaction to obtain reduced powder;

soaking the reduced powder in a hydrochloric acid solution, and then carrying out solid-liquid separation to obtain solid powder;

and etching to remove the residual magnesium powder in the solid powder to obtain the hollow silicon ball containing the template agent.

6. The method according to claim 5, wherein in step S2, the weight ratio of the hollow silica spheres to the magnesium powder to the sodium chloride is 1: 0.8-0.9: 10-12.

7. The method of claim 5, wherein the reduction step comprises: heating the mixed powder to 680-720 ℃ in inert gas, preserving heat for 4-5 h, and then cooling to room temperature; and then soaking the cooled powder in a hydrochloric acid solution, and performing centrifugal separation to obtain the reduced powder.

8. The method according to claim 7, wherein an etchant used in the step of removing the residual magnesium powder by etching is hydrofluoric acid.

9. The production method according to any one of claims 1 to 8, wherein the step S3 includes:

adding ammonia water and the hollow silicon spheres containing the template agent into a second reaction solvent to form a suspension;

adding tetrabutyl titanate into the suspension for a second precipitation reaction to obtain a second product system;

carrying out centrifugal separation on the second product system to obtain TiO_2-xAnd (3) coating the hollow silicon spheres.

10. The preparation method according to claim 9, wherein the weight ratio of ammonia water to tetrabutyl titanate is 1: 1.5-1: 2, 0.333-0.5 g of the hollow silica spheres containing the template agent is used per ml of ammonia water, and the mass concentration of the ammonia water is 28-35%.

11. The method according to any one of claims 1 to 10, wherein the TiO is calcined in step S4_2-xThe step of coating the hollow silicon spheres comprises: subjecting the TiO to a reaction_2-xAnd heating the coated hollow silicon spheres to 500-900 ℃ in an inert atmosphere, and preserving the heat for 4-5 hours to obtain the titanium oxide coated porous hollow silicon spheres.

12. The titanium oxide-coated porous hollow silicon spheres prepared by the preparation method of any one of claims 1 to 11.

13. Use of the titanium oxide-coated porous hollow silicon spheres of claim 12 as a negative electrode material for lithium ion batteries.

Technical Field

The invention relates to the field of lithium ion battery materials, in particular to a titanium oxide coated porous hollow silicon ball, and a preparation method and application thereof.

Background

Silicon has a specific capacity 10 times higher than that of graphite and is rich in storage, and most possibly replaces graphite to become a next-generation lithium ion negative electrode material. However, the large volume change of silicon during cycling can cause particle pulverization and repeated formation of a solid electrolyte interfacial film, seriously affecting its cycle life. In addition, silicon has poor conductivity, which affects its rate capability. Therefore, structural modifications of silicon, such as surface coating of silicon, are often required.

Coating the silicon surface with carbon can improve the conductivity of the composite, and the carbon layer can act as a barrier to prevent direct contact of the silicon with the electrolyte. However, since the volume of silicon varies greatly during the cycle and the strength of amorphous carbon is low, the carbon layer tightly coated on the silicon surface is easily broken during the cycle, and thus a good coating effect cannot be achieved. In addition, high-temperature calcination is needed in the process of forming the carbon layer, and products such as SiC which are not favorable for electrochemical performance are easily generated.

The stress caused by volume expansion can be relieved by carrying out nano treatment on the silicon, so that pulverization of the material is avoided. The design of structures such as silicon nanoparticles, silicon nano-films, silicon nanotubes, silicon nanowires and the like is beneficial to reducing volume expansion. The hollow nanospheres have larger cavities and thin shells, and can relieve the stress caused by volume expansion and shorten the diffusion path of electrolyte and lithium ions. However large surface of hollow nanospheresThe area and the surface are in contact with an electrolyte solution to consume lithium ions and the SEI film is repeatedly generated. The common method for preparing hollow nano silicon spheres is chemical vapor deposition and solid SiO₂As template, SiO at high temperature₂Depositing the surface, and then depositing SiO₂And etching off to obtain the hollow nanospheres. However, this method uses toxic and flammable silane as a raw material and is not environmentally friendly.

For the above reasons, there is a need to provide a new process for modifying silicon material, so as to better overcome the defects of poor conductivity and large volume change in the cycle process, and make it better serve as the negative electrode material of lithium ion battery. Meanwhile, toxic and flammable silane is required to be avoided as a raw material, so that the preparation process is more environment-friendly.

Disclosure of Invention

The invention mainly aims to provide a titanium oxide coated porous hollow silicon ball, a preparation method and application thereof, and aims to solve the problems of poor electrical cycle performance caused by poor conductivity and large volume change in a cycle process when a silicon material is used as a lithium ion battery cathode material in the prior art and the problem of insufficient environmental protection in the preparation process.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing titanium oxide-coated porous hollow silicon spheres, comprising the steps of: s1, preparing hollow silica spheres containing the template agent by adopting a sol-gel method; s2, mixing the hollow SiO₂Carrying out magnesiothermic reduction on the spheres to obtain hollow silicon spheres containing the template agent; s3, coating TiO on the surface of the hollow silicon ball_2-xWherein x is 0-0.6, to obtain TiO_2-xA coated hollow silicon sphere; s4, calcining TiO_2-xAnd coating the hollow silicon spheres to obtain the titanium oxide coated porous hollow silicon spheres.

Further, step S1 includes: dissolving ammonia water and a template agent in a first reaction solvent to form a pre-reaction system; adding tetraethoxysilane into the pre-reaction system to carry out a first precipitation reaction to obtain a first product system; and (3) aging and centrifugally separating the first product system to obtain the hollow silica spheres containing the template agent.

Further, the template agent is cetyl trimethyl ammonium bromide; preferably, the volume ratio of the ammonia water to the ethyl orthosilicate is 1: 1-1: 2, 0.15-0.2 g of the template agent is used for each milliliter of ammonia water, and the mass concentration of the ammonia water is 28-35%.

Further, the temperature of the first precipitation reaction is 30-50 ℃, and the time of the first precipitation reaction is 24-36 hours; preferably, the first reaction solvent is a mixed solvent of ethanol and deionized water; preferably, the aging temperature in the aging step is 90-95 ℃.

Further, step S2 includes: mixing the hollow silica spheres, magnesium powder and sodium chloride to obtain mixed powder; placing the mixed powder in an inert environment for reduction reaction to obtain reduced powder; soaking the reduced powder in a hydrochloric acid solution, and then carrying out solid-liquid separation to obtain solid powder; and etching to remove the residual magnesium powder in the solid powder to obtain the hollow silicon ball containing the template agent.

Further, in step S2, the weight ratio of the hollow silica spheres, the magnesium powder and the sodium chloride is 1: 0.8-0.9: 10-12.

Further, the reduction reaction step comprises: heating the mixed powder in inert gas to 680-720 ℃, preserving heat for 4-5 h, and then cooling to room temperature; and then soaking the cooled powder in a hydrochloric acid solution, and performing centrifugal separation to obtain reduced powder.

Further, in the step of removing the residual magnesium powder by etching, hydrofluoric acid is used as an etchant.

Further, step S3 includes: adding ammonia water and hollow silicon spheres containing a template agent into a second reaction solvent to form a suspension; adding tetrabutyl titanate into the suspension for a second precipitation reaction to obtain a second product system; carrying out centrifugal separation on the second product system to obtain TiO_2-xCoated hollow silicon spheres.

Furthermore, the weight ratio of the ammonia water to the tetrabutyl titanate is 1: 1.5-1: 2, 0.333-0.5 g of hollow silicon spheres containing the template agent is corresponding to each milliliter of ammonia water, and the mass concentration of the ammonia water is 28-35%.

Further, in step S4, the TiO is calcined_2-xCoated hollow siliconThe steps of the ball include: adding TiO into the mixture_2-xAnd heating the coated hollow silicon spheres to 500-900 ℃ in an inert atmosphere, and preserving the heat for 4-5 hours to obtain the titanium oxide coated porous hollow silicon spheres.

According to another aspect of the invention, the titanium oxide coated porous hollow silicon spheres prepared by the preparation method are also provided.

According to another aspect of the invention, the application of the titanium oxide coated porous hollow silicon ball as a lithium ion battery negative electrode material is also provided.

The invention provides a preparation method of a titanium oxide coated porous hollow silicon ball. Secondly, coating TiO on the surface of the hollow silicon ball_2-xForm a surface coating with non-stoichiometric TiO_2-xFinally, the template agent is removed by calcining to form the titanium oxide coated porous hollow silicon spheres. TiO2₂Small volume change (less than 4%) in the circulation process, good stability, and TiO₂The strength is much higher than amorphous carbon. In addition, TiO in non-stoichiometric proportions_2-xThe composite material has good structural stability, small energy gap and high conductivity, so that the electrochemical performance of the silicon-based material can be improved by compounding the composite material with porous hollow silicon spheres. Therefore, the titanium oxide coated porous hollow silicon spheres prepared by the method well solves the problems of poor conductivity and large volume change in the circulation process of the hollow silicon spheres, has good point circulation performance, and is very suitable for being used as a lithium ion battery cathode material. In addition, the silica spheres are prepared by using a sol-gel method, toxic and flammable silane is not used as a raw material, and the method is environment-friendly and more suitable for industrial application.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 shows (a) SEM photographs and (b) HRSEM photographs of the hollow silica spheres containing the template prepared in example 1 according to the present invention;

fig. 2 shows (a) SEM photographs and (b) HRSEM photographs of the hollow silicon spheres prepared in example 1 according to the present invention;

FIG. 3 shows XRD patterns of hollow silicon spheres and titania-coated porous hollow silicon spheres prepared in example 1 according to the present invention;

FIG. 4 shows titania-coated porous hollow silica spheres and TiO prepared in example 1 according to the present invention₂XPS Ti2p spectra of (A), wherein FIG. 4(a) is the XPS Ti2p spectra of the titanium oxide coated porous hollow silicon spheres and FIG. 4(a) is the XPS Ti2p spectra of the TiO coated porous hollow silicon spheres₂XPS Ti2p spectrum of;

FIG. 5 shows N of hollow silicon spheres and titanium oxide-coated porous hollow silicon spheres prepared in example 1 according to the present invention₂Adsorption/desorption curves and pore size distribution diagrams, wherein FIG. 5(a) is N of hollow silicon spheres₂An adsorption/desorption curve, in which FIG. 5(b) is a pore size distribution diagram of the hollow silicon spheres and FIG. 5(c) is an N-type pore size distribution diagram of the titanium oxide-coated porous hollow silicon spheres₂An adsorption/desorption curve, and fig. 5(d) is a pore size distribution diagram of the titanium oxide-coated porous hollow silicon spheres;

fig. 6 shows a charge and discharge graph of the titania-coated porous hollow silica spheres prepared in example 1 according to the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As described in the background art, in the prior art, when a silicon material is used as a negative electrode material of a lithium ion battery, the electrical cycle performance is not good due to poor conductivity and large volume change in the cycle process, and the preparation process is not environment-friendly.

In order to solve the problem, the invention provides a preparation method of titanium oxide coated porous hollow silicon spheres, which comprises the following steps: s1, preparing hollow silica spheres containing the template agent by adopting a sol-gel method;s2, mixing the hollow SiO₂Carrying out magnesiothermic reduction on the spheres to obtain hollow silicon spheres containing the template agent; s3, coating TiO on the surface of the hollow silicon ball_2-xWherein x is 0-0.6, to obtain TiO_2-xA coated hollow silicon sphere; s4, calcining TiO_2-xAnd coating the hollow silicon spheres to obtain the titanium oxide coated porous hollow silicon spheres.

The preparation method provided by the invention comprises the steps of preparing the hollow silica spheres containing the template agent by a sol-gel method, and reducing the silica into silicon by a magnesiothermic reduction method to form the hollow silica spheres containing the template agent. Secondly, coating TiO on the surface of the hollow silicon ball_2-xForm a surface coating with non-stoichiometric TiO_2-xFinally, the template agent is removed by calcining to form the titanium oxide coated porous hollow silicon spheres. TiO2₂Small volume change (less than 4%) in the circulation process, good stability, and TiO₂The strength is much higher than amorphous carbon. In addition, TiO in non-stoichiometric proportions_2-xThe composite material has good structural stability, small energy gap and high conductivity, so that the electrochemical performance of the silicon-based material can be improved by compounding the composite material with porous hollow silicon spheres. Therefore, the present invention effectively utilizes TiO_2-XThe prepared titanium oxide coated porous hollow silicon ball has the advantages that the titanium oxide coated porous hollow silicon ball is combined with the porous hollow silicon ball to form an internal buffer structure, the problems of poor conductivity and large volume change in the circulation process of the hollow silicon ball are well solved, the titanium oxide coated porous hollow silicon ball has good point circulation performance, and the titanium oxide coated porous hollow silicon ball is very suitable for being used as a lithium ion battery cathode material. In addition, the silica spheres are prepared by using a sol-gel method, toxic and flammable silane is not used as a raw material, and the method is environment-friendly and more suitable for industrial application.

In particular, the invention is to reduce the hollow silicon dioxide spheres into hollow silicon spheres by magnesium thermal reduction after the step of preparing the hollow silicon dioxide spheres. Compared with the coating of TiO_2-xAnd then, the magnesium thermal reduction is carried out, so that the reduction effect on the silicon dioxide is better. And after magnesiothermic reduction, TiO₂The coating effect of the coating layer is better.

The step of preparing the silica spheres by the sol-gel method may be a conventional process of sol-gel method, and in a preferred embodiment, the step S1 includes: dissolving ammonia water and a template agent in a first reaction solvent to form a pre-reaction system; adding tetraethoxysilane into the pre-reaction system to carry out a first precipitation reaction to obtain a first product system; and (3) aging and centrifugally separating the first product system to obtain the hollow silica spheres containing the template agent. The sol-gel precipitation reaction is more stable in the step, and the prepared silicon dioxide spheres have more uniform particle size, so that the electrical cycle performance of the final cathode material is further improved.

In a preferred embodiment, the templating agent is cetyltrimethylammonium bromide. Preferably, the volume ratio of the ammonia water to the ethyl orthosilicate is 1: 1-1: 2, 0.15-0.2 g of the template agent is used for each milliliter of ammonia water, and the mass concentration of the ammonia water is 28-35%. The relation of the use amount of the raw materials is controlled within the range, so that the conversion rate and the yield of the sol-gel precipitation reaction are improved, and the reaction efficiency is improved. More preferably, the temperature of the first precipitation reaction is 30-36 ℃, and the time of the first precipitation reaction is 24-36 hours; preferably, the first reaction solvent is a mixed solvent of ethanol and deionized water; preferably, the aging temperature in the aging step is 90-95 ℃.

In a preferred embodiment, step S2 includes: mixing the hollow silica spheres, magnesium powder and sodium chloride to obtain mixed powder; placing the mixed powder in an inert environment for reduction reaction to obtain reduced powder; soaking the reduced powder in a hydrochloric acid solution, and then carrying out solid-liquid separation to obtain solid powder; and etching to remove the residual magnesium powder in the solid powder to obtain the hollow silicon ball containing the template agent. Under the process, the silicon dioxide can be fully reduced into silicon, and hollow silicon spheres with stable structures are formed.

In order to further improve the reduction effect, in a preferred embodiment, in step S2, the weight ratio of the hollow silica spheres, the magnesium powder and the sodium chloride is 1: 0.8-0.9: 10-12. More preferably, the reduction step comprises: heating the mixed powder in inert gas to 680-720 ℃, preserving heat for 4-5 h, and then cooling to room temperature; and then soaking the cooled powder in a hydrochloric acid solution, and performing centrifugal separation to obtain reduced powder. The magnesium thermal reduction is carried out under the temperature and the conditions, and the reduction is more sufficient. And soaking the cooled powder in a hydrochloric acid solution to dissolve and remove the residual sodium chloride in the reaction.

In a preferred embodiment, in the step of removing the residual magnesium powder by etching, the etchant used is hydrofluoric acid. And residual magnesium carried in the hollow silicon spheres can be more fully etched and removed by adopting hydrofluoric acid.

In a preferred embodiment, step S3 includes: adding ammonia water and hollow silicon spheres containing a template agent into a second reaction solvent to form a suspension; adding tetrabutyl titanate into the suspension for a second precipitation reaction to obtain a second product system; carrying out centrifugal separation on the second product system to obtain TiO_2-xCoated hollow silicon spheres. By adopting the step to coat the titanium oxide, the coating process is more stable, and a more uniform titanium oxide coating layer can be formed on the surface of the hollow silicon ball. More preferably, the weight ratio of the ammonia water to the tetrabutyl titanate is 1: 1.5-1: 2, 0.333-0.5 g of hollow silicon spheres containing the template agent is corresponding to each milliliter of ammonia water, and the mass concentration of the ammonia water is 28-35%.

In a preferred embodiment, in step S4, the TiO is calcined_2-xThe steps of coating the hollow silicon spheres include: adding TiO into the mixture_2-xAnd heating the coated hollow silicon spheres to 500-900 ℃ in an inert atmosphere, and preserving the heat for 4-5 hours to obtain the titanium oxide coated porous hollow silicon spheres. Under the calcination process, the template agent is removed more thoroughly.

The inert gas used in the above preparation method may be argon gas.

According to another aspect of the invention, the titanium oxide coated porous hollow silicon spheres prepared by the preparation method are provided. The titanium oxide coated porous hollow silicon ball has better conductivity and small volume change in the circulating process, and is very suitable for being used as a lithium ion battery cathode material.

According to another aspect of the invention, the application of the titanium oxide coated porous hollow silicon spheres as the negative electrode material of the lithium ion battery is also provided.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.

Example 1

4ml of 28 mass% ammonia water and 0.6g of cetyltrimethylammonium bromide (CTAB) were added to a mixed solvent containing 120ml of anhydrous ethanol and 200ml of deionized water, and ultrasonication was carried out for 15min to completely dissolve CTAB. 4ml of Tetraethylorthosilicate (TEOS) were added dropwise to the above liquid with vigorous stirring and stirred in a water bath at 30 ℃ for 24h at 500 rpm. The precipitate after the reaction was centrifuged and washed 3 times with water and absolute ethanol to remove unreacted TEOS and residual ammonia. The centrifuged precipitate was then dispersed in 400ml of deionized water by sonication, aged in a water bath at 90 ℃ for 24h, and the precipitate was centrifuged and washed 3 times with deionized water. Dispersing the precipitate in 320ml of anhydrous ethanol by ultrasonic treatment, adding 900ml of HCI solution with the mass fraction of 37%, stirring for 3h in a water bath at 60 ℃ at the rotating speed of 500rpm, centrifugally separating the precipitate, and drying for 6h in an oven at 80 ℃ to obtain HSiO₂The SEM photograph of the hollow silica spheres is shown in FIG. 1(a), and the HRSEM photograph is shown in FIG. 1 (b).

1g of HSiO₂0.8g of magnesium powder and 10g of NaCl are ground for 30min to be uniformly mixed. And filling the mixed powder into a stainless steel tube, introducing Ar gas, and sealing the stainless steel tube. The stainless steel tube was then placed in a tube furnace under Ar atmosphere for 3 min. The temperature rising rate of (1) is from room temperature to 680 ℃, and the temperature is kept for 4 hours and then the temperature is cooled to room temperature. Soaking the powder in the stainless steel tube in 150ml of 1mol/L hydrochloric acid solution, centrifuging and separating precipitates after 5h, soaking the precipitates in 100ml of hydrofluoric acid solution with the mass fraction of 5% for etching for 30min, centrifuging and separating the precipitates, washing the precipitates for 3 times respectively by using deionized water and absolute ethyl alcohol, and finally drying the obtained precipitates in a vacuum oven at 80 ℃ for 6h to obtain MHSi hollow silicon spheres, wherein the SEM picture is shown in figure 2(a), and the HRSEM picture is shown in figure 2 (b).

Adding 0.3ml of 28 mass percent ammonia water and 100mg of MHSi into 100ml of absolute ethyl alcohol, carrying out ultrasonic treatment for 15min, stirring the suspension in a water bath at 45 ℃ at the rotating speed of 600rpm, dropwise adding 0.45ml of tetrabutyl titanate (TBOT) into the suspension within 10min, and then adjusting the rotating speed to 400rpm and continuing stirring for 12 h. And (3) centrifugally separating the precipitate after reaction, washing the precipitate for 3 times by using absolute ethyl alcohol and deionized water respectively, and drying the precipitate in a vacuum oven at the temperature of 100 ℃ for 6 hours. The dried precipitate was placed in a crucible and placed in a tube furnace under Ar atmosphere for 30 min. Heating the titanium oxide-coated porous hollow silica spheres to 500 ℃, 600 ℃, 700 ℃, 800 ℃ and 900 ℃ respectively at the heating rate from room temperature, preserving the heat for 4 hours, and then cooling the titanium oxide-coated porous hollow silica spheres to room temperature to obtain the final product, namely the titanium oxide-coated porous hollow silica spheres MHSi @ TiO 2.

FIG. 3 shows XRD patterns of the above hollow silicon spheres and titania-coated porous hollow silicon spheres; as can be seen from the figure, at 111, 220, 311, 400, 311, respectively corresponding to 26 °, 47 °, 56 °, 70 °, 76 °, the peak shape indicates that silicon exists in the form of elemental silicon in the composite material. The peak pattern of anatase titanium oxide is typical and is compared with a standard graph to prove the above conclusion.

FIG. 4 shows titanium oxide coated porous hollow silica spheres and TiO₂Wherein FIG. 4(a) is an XPS Ti2p spectrum (diffraction energy curve) of the porous hollow silicon spheres coated with titanium oxide, and FIG. 4(a) is a TiO₂XPS Ti2p spectra of (a); as can be seen from the figure, the typical bond of titanium oxide is Ti³⁺And Ti⁴⁺From the bond strength, the analysis shows that Si-Ti-O bond is formed with silicon, and the bonding force is strong.

FIG. 5 shows hollow silicon spheres and N of titania-coated porous hollow silicon spheres₂Adsorption/desorption curves and pore size distribution diagrams, wherein FIG. 5(a) is N of hollow silicon spheres₂An adsorption/desorption curve, in which FIG. 5(b) is a pore size distribution diagram of the hollow silicon spheres and FIG. 5(c) is an N-type pore size distribution diagram of the titanium oxide-coated porous hollow silicon spheres₂An adsorption/desorption curve, and fig. 5(d) is a pore size distribution diagram of the titanium oxide-coated porous hollow silicon spheres; as can be seen from the figure, the particle size distribution is relatively uniform, the specific surface area is large, and the porous lithium ion battery is very suitable for the insertion and extraction of lithium ions and is in a porous state.

FIG. 6 is a graph showing charge and discharge curves of titania-coated porous hollow silica spheres prepared in example 1 according to the present invention; as can be seen from the figure, the capacity of the material reaches 2400mah/g, and after 50 weeks of circulation, the capacity is still maintained at 1600 mah/g.

Example 2

2g of HSiO2, 2.6g of magnesium powder and 15g of KCl are ground for 30min to be uniformly mixed. And filling the mixed powder into a stainless steel tube, introducing Ar gas, and sealing the stainless steel tube. The stainless steel tube was then placed in a tube furnace under Ar atmosphere for 5 deg.C min. The temperature rising rate of (1) is from room temperature to 720 ℃, and the temperature is kept for 4h and then the temperature is cooled to room temperature. Soaking the powder in the stainless steel tube in 300ml of 1mol/L hydrochloric acid solution, centrifuging and separating the precipitate after 4h, soaking the precipitate in 200ml of hydrofluoric acid solution with the mass fraction of 5% for etching for 30min, centrifuging and separating the precipitate, washing the precipitate for 3 times by using deionized water and absolute ethyl alcohol respectively, and finally drying the obtained precipitate in a vacuum oven at 80 ℃ for 6h to obtain the MHSi hollow silicon ball.

Adding 0.5ml of 28 mass percent ammonia water and 200mg of MHSi into 100ml of absolute ethyl alcohol, carrying out ultrasonic treatment for 15min, stirring the suspension in a water bath at 60 ℃ at the rotating speed of 600rpm, dropwise adding 0.45ml of tetrabutyl titanate (TBOT) into the suspension within 10min, and then adjusting the rotating speed to 400rpm and continuing stirring for 12 h. And (3) centrifugally separating the precipitate after reaction, washing the precipitate for 3 times by using absolute ethyl alcohol and deionized water respectively, and drying the precipitate in a vacuum oven at the temperature of 100 ℃ for 6 hours. The dried precipitate was placed in a crucible and placed in a tube furnace under Ar atmosphere for 30 min. Heating the mixture from room temperature to 500 ℃, 600 ℃, 700 ℃, 800 ℃ and 900 ℃, preserving the heat for 5 hours, and then cooling the mixture to room temperature to obtain the final product titanium oxide coated porous hollow silica spheres MHSi @ TiO₂。

The detection proves that the capacity of the material reaches 2100mah/g, and after 50-week circulation, the capacity is still maintained at 1500 mah/g.

Comparative example 1

3g of HSiO₂0.8g of magnesium powder and 16g of NaCl are ground for 30min to be uniformly mixed. And filling the mixed powder into a stainless steel tube, introducing Ar gas, and sealing the stainless steel tube. The stainless steel tube was then placed in a tube furnace under Ar atmosphere for 3 min. The temperature rising rate of (1) is from room temperature to 750 ℃, and the temperature is kept for 2h and then the temperature is cooled to room temperature. Into a stainless steel pipeSoaking the powder in 180ml of 1mol/L hydrochloric acid solution, centrifugally separating the precipitate after 4h, soaking the precipitate in 100ml of 5% hydrofluoric acid solution for etching for 25min, centrifugally separating the precipitate, washing the precipitate for 3 times by using deionized water and absolute ethyl alcohol respectively, and finally drying the obtained precipitate in a vacuum oven at 80 ℃ for 5h to obtain the MHSi hollow silicon spheres.

The hollow silicon spheres are washed in absolute ethyl alcohol for 3 minutes, put into an oven for drying for 1 hour, and sieved to obtain powder with the particle size D50 of about 20 microns, and the gram volume is tested by a half cell.

The detection proves that the capacity of the composite material is only 1200mah/g, and after circulation, the capacity loss is only 500 mah/g.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.