CN111477858A - Si @ TiO2Preparation method of hollow core-shell composite material - Google Patents

Abstract

The invention belongs to the technical field of lithium battery electrode materials, and discloses a preparation method of a Si@TiO ₂ hollow core-shell composite material, comprising the following steps: (1) taking a certain amount of silicon nanoparticles, dissolving them in a glucose solution, and ultrasonically mixing; (2) transferring the mixed solution A into a hydrothermal reaction kettle, and performing a hydrothermal reaction to obtain a Si/C composite material precursor; (3) dissolving the Si/C composite material precursor in a certain amount of titanium source solution , aged for 8-12h, and dried in vacuum to obtain Si/C/TiO ₂ precursor; (4) calcining Si/C/TiO ₂ precursor in air to obtain Si@TiO ₂ hollow composite material. The method is simple in process and convenient in control of conditions, and obtains a Si@TiO ₂ hollow core-shell structure with uniform size and good dispersion, which can be used as a negative electrode material to improve the rate performance and cycle stability of lithium-ion batteries.

Description

A kind of preparation method of Si@TiO2 hollow core-shell composite

technical field

The invention relates to the technical field of battery anode material, in particular to a preparation method of a Si@TiO ₂ hollow core-shell composite material.

Background technique

Lithium-ion batteries have the advantages of high working voltage, high specific energy, stable discharge, small size and light weight, and have shown broad application prospects in the fields of portable electronic equipment, electric vehicles, space technology and other fields. At present, the graphite negative electrode used in commercialization Materials, the actual specific capacity is close to the theoretical value of 372mAh/g, it is difficult to meet the higher requirements of green energy technology and low-carbon economic development for the next generation of lithium-ion batteries, so the development of high specific capacity anode materials has become a research topic in lithium-ion batteries. an important direction. Silicon can form various forms of alloys with lithium, the theoretical lithium storage capacity is as high as 4200mAh/g, the lithium intercalation potential is low, and it has a high abundance in the earth's crust, so it is an ideal negative electrode material. However, during the charging and discharging process, the lithium deintercalation reaction of silicon is accompanied by a huge volume change (~300%), resulting in the rupture and pulverization of the silicon particles, resulting in separation between the silicon particles and between the silicon particles and the current collector, resulting in loss of electricity. contact, resulting in capacity fading and a sharp drop in cycle performance. Therefore, improving the cycle performance of silicon-based anode materials is a research hotspot.

Carbon coating after nano-sized silicon particles is an effective way to solve the volume expansion of silicon and improve the cycle performance of silicon-based anode materials. However, when the charge and discharge reaches a certain level, the stress generated by the volume deformation of silicon lithiation can easily lead to the rupture of the carbon shell, so the cycle stability of the silicon-carbon composite anode material still cannot meet the requirements of industrial application. Titanium dioxide, as a negative electrode material for lithium ion batteries, has a small change in structure and volume (~4%) during the process of lithium extraction and intercalation, and has stable cycle performance, and can be used as a coating material for silicon nanoparticles.

The Chinese invention patent with publication number CN106784714A discloses a silicon-based composite negative electrode material for lithium ion batteries and a preparation method thereof. The composite material not only has a high specific capacity, but also has excellent first-week coulombic efficiency and cycle stability performance, but its process is complex, the reaction conditions are strictly controlled, the product uniformity is not high, and the production cost is high. The Chinese invention patent with publication number CN106848276A discloses a core-shell structure titanium dioxide-coated silicon lithium-ion battery negative electrode material and a preparation method thereof. After the silicon powder is reacted with ammonium fluorotitanate under hydrothermal conditions, the obtained product is further heat-treated, That is, a core-shell structure titanium dioxide-coated silicon lithium-ion battery negative electrode material with titanium dioxide as an outer shell, silicon nanoparticles as an inner core, and a cavity between the outer shell and the inner core is obtained. The preparation method of the invention is simple and effective. The prepared silicon-based negative electrode material has an outer shell of titanium dioxide with stable structure in the process of lithium deintercalation, an inner core of silicon element that can provide high specific capacity, and a layer between the core and shell that can buffer silicon deintercalation. The cavity with volume effect in the process of lithium intercalation has good lithium storage performance. However, from the TEM pictures provided by the invention, the silicon/titanium dioxide composite material has poor dispersibility angle, and there are problems such as irregular morphology and secondary agglomeration.

SUMMARY OF THE INVENTION

In view of the above content, the purpose of the present invention is to provide a preparation method of Si@TiO ₂ hollow core-shell composite material, the method is simple in process, convenient in condition control, and obtains a Si@TiO ₂ hollow core-shell structure with uniform size and dispersion It has good performance and can be used as anode material to improve the rate performance and cycle stability of lithium-ion batteries.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) get a certain amount of silicon nanoparticles, dissolve in glucose solution, ultrasonic for 20min-60min, get mixed solution A;

(2) transferring the mixed solution A into a hydrothermal reaction kettle, and reacting for 5-10 h under the condition of a hydrothermal temperature of 150°C-200°C to obtain a Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a certain amount of titanium source solution, aging for 8-12 hours, and vacuum drying to obtain the Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor is calcined in air for 1-4 hours, and the calcination temperature is 500° C.-600° C. to obtain a Si@TiO ₂ hollow composite material.

In the present invention, preferably, the particle size of the silicon nanoparticles is less than 100 nm.

In the present invention, preferably, the concentration of glucose in the glucose solution is 0.1-0.2 mol/L, and the mass ratio of silicon nanoparticles to glucose is 1:5-10.

In the present invention, preferably, the titanium source in the step (3) is a titanium tetrachloride solution, a titanium sulfate solution, a tetrabutyl titanate solution, and a titanium isopropoxide solution with a concentration of 0.1-0.2 mol/L. one or more of.

In the present invention, preferably, in the step (3), the mass ratio of the silicon nanoparticles to the solute in the titanium source is controlled to be 1:5-10.

In the present invention, preferably, in the step (3), the aging is performed under a stirring condition of a rotational speed of 300-500 rpm.

The Si@ _TiO2 hollow core-shell composites prepared above can be used as silicon-based anode materials for lithium-ion batteries.

The present invention has the following beneficial effects:

1. According to the technical solution of the present invention, Si@C@TiO ₂ precursor is obtained by simple hydrothermal method and solvothermal method, and Si@TiO ₂ hollow core-shell structure is obtained by high temperature heat treatment. TiO ₂ has excellent mechanical stability and can be The volume expansion during the charging and discharging process of Si is avoided, and the Si@TiO ₂ hollow structure can alleviate the internal stress generated by the volume effect of Si, avoid the damage of the material structure, and improve the cycle stability of the material.

2. The method of the present invention has the advantages of simple process, convenient condition control and low production cost. By controlling the ratio of raw materials and reaction conditions, the obtained Si@ _TiO2 hollow core-shell structure has uniform size, regular morphology, good dispersibility, and almost no damage and collapse, thus further ensuring the stability of the material.

Description of drawings

Fig. 1 is the lens diagram of the composite material prepared by the present invention;

FIG. 2 is a lens diagram of the composite material prepared in Comparative Example 1. FIG.

Detailed ways

In order to express the present invention more clearly, the present invention will be further described below through specific examples.

Example 1

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) Take silicon nanoparticles with a particle size of less than 100 nm, dissolve them in a glucose solution with a concentration of 0.1 mol/L, control the mass ratio of silicon nanoparticles to glucose to be 1:5, and ultrasonically disperse them for 20 minutes to obtain mixed solution A;

(2) Transfer the mixed solution A into a hydrothermal reaction kettle, and react for 10 h under the condition of a hydrothermal temperature of 150 °C to obtain a Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a titanium tetrachloride solution with a concentration of 0.1 mol/L, controlling the mass ratio of the silicon nanoparticles to the solute in the titanium source to be 1:5, at a rotational speed of 300 rpm Aged for 12h under the stirring condition of 100%, and dried in vacuum to obtain the Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor was calcined in air for 1 h, and the calcination temperature was 600° C. to obtain the Si@TiO ₂ hollow composite material.

Example 2

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) Take silicon nanoparticles with a particle size of less than 100 nm, dissolve them in a glucose solution with a concentration of 0.12 mol/L, control the mass ratio of silicon nanoparticles to glucose to be 1:5, and ultrasonically disperse for 50 min to obtain mixed solution A;

(2) Transfer the mixed solution A into a hydrothermal reaction kettle, and react for 9 h under the condition of a hydrothermal temperature of 160° C. to obtain a Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a titanium sulfate solution with a concentration of 0.12 mol/L; controlling the mass ratio of the silicon nanoparticles to the solute in the titanium source to be 1:6; stirring at a rotational speed of 350 rpm Aging under conditions for 11h, vacuum drying to obtain Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor was calcined in air for 2 h, and the calcination temperature was 580° C. to obtain the Si@TiO ₂ hollow composite material.

Example 3

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) Take silicon nanoparticles with a particle size of less than 100 nm, dissolve them in a glucose solution with a concentration of 0.15 mol/L, control the mass ratio of silicon nanoparticles to glucose to be 1:8, and ultrasonically disperse them for 40 minutes to obtain mixed solution A;

(2) Transfer the mixed solution A to the hydrothermal reaction kettle, and react for 7 h under the condition of the hydrothermal temperature of 165 °C to obtain the Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a tetrabutyl titanate solution with a concentration of 0.16 mol/L, and controlling the mass ratio of the silicon nanoparticles to the solute in the titanium source to be 1:7; Aged for 9 h under stirring conditions of 400 rpm and vacuum dried to obtain Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor was calcined in air for 3 h, and the calcination temperature was 540° C. to obtain the Si@TiO ₂ hollow composite material.

Example 4

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) Take silicon nanoparticles with particle size < 100 nm, dissolve them in a glucose solution with a concentration of 0.18 mol/L, control the mass ratio of silicon nanoparticles to glucose to be 1:9, and ultrasonically disperse for 20 min to obtain mixed solution A;

(2) Transfer the mixed solution A into a hydrothermal reaction kettle, and react for 6 hours under the condition of a hydrothermal temperature of 190° C. to obtain a Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a titanium isopropoxide solution with a concentration of 0.18mol/L, and controlling the mass ratio of the silicon nanoparticles to the solute in the titanium source to be 1:8; Aged for 11h under the stirring condition of 100°C, and dried in vacuum to obtain the Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor was calcined in air for 4 h, and the calcination temperature was 530° C. to obtain the Si@TiO ₂ hollow composite material.

Example 5

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) Take silicon nanoparticles with a particle size of less than 100 nm, dissolve them in a glucose solution with a concentration of 0.2 mol/L, control the mass ratio of silicon nanoparticles to glucose to be 1:10, and ultrasonically disperse for 30 min to obtain mixed solution A;

(2) Transfer the mixed solution A into a hydrothermal reaction kettle, and react for 5 h under the condition of a hydrothermal temperature of 200° C. to obtain a Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a titanium tetrachloride solution with a concentration of 0.2 mol/L and a mixed solution of 0.1 mol/L titanium sulfate solution to control the solutes in the silicon nanoparticles used and the titanium source The mass ratio is 1:10, aged for 12h under the stirring condition of the rotating speed of 300rpm, and vacuum dried to obtain the Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor was calcined in air for 4 h, and the calcination temperature was 500° C. to obtain the Si@TiO ₂ hollow composite material.

Comparative Example 1

A preparation method of Si@TiO ₂ hollow core-shell composite material, comprising the following steps:

(1) Take silicon nanoparticles with a particle size of less than 100 nm, dissolve them in a glucose solution with a concentration of 0.2 mol/L, control the mass ratio of silicon nanoparticles to glucose to be 1:1, and ultrasonically disperse for 30 min to obtain mixed solution A;

(2) Transfer the mixed solution A into a hydrothermal reaction kettle, and react for 5 h under the condition of a hydrothermal temperature of 200° C. to obtain a Si/C composite material precursor;

(3) Dissolving the Si/C composite material precursor in a titanium tetrachloride solution with a concentration of 0.2 mol/L and a mixed solution of 0.1 mol/L titanium sulfate solution to control the solutes in the silicon nanoparticles used and the titanium source The mass ratio is 1:1, aged for 12h under the stirring condition of the rotating speed of 300rpm, and vacuum dried to obtain the Si/C/TiO ₂ precursor;

(4) The Si/C/TiO ₂ precursor was calcined in air for 4 h, and the calcination temperature was 500° C. to obtain the Si@TiO ₂ hollow composite material.

Performance Testing:

1. The composite materials prepared in Examples 1-5 and Comparative Example 1 are subjected to lens scanning test. The lens diagram of the material prepared in Example 1-5 is shown in Figure 1, and the diagram of the composite material lens prepared in Comparative Example 1 is shown in Figure 2. It can be seen that It was found that the materials prepared in Examples 1-5 formed a hollow core-shell structure with uniform size, regular morphology, good dispersion, and almost no damage and collapse. The material prepared in Comparative Example 1 had poor nucleation effect, and was damaged and collapsed.

2. The Si@TiO ₂ hollow composite materials prepared in Examples 1-5 and Comparative Example 1 were used as negative electrodes respectively; the negative electrode materials, the conductive agent and the binder were mixed and dissolved in a solvent in a mass ratio of 18:1:2, The solid content was controlled at 45%, coated on the copper foil current collector, and vacuum-dried to obtain a negative pole piece; the lithium piece was used as the counter electrode, the solute in the electrolyte was 1mol/L LiPF6, and the solvent was 1:1 by volume. The mixed solvent of EC and DMC, the diaphragm is Celgard2400 film, assembled into CR2025 type button battery according to the conventional process, and numbered S1-S5 and D1 respectively, placed in the battery tester to test the charge-discharge performance of the prepared battery, The charge-discharge cycle test (charge-discharge voltage 2.5-4.0V) was carried out according to the charge-discharge rate of 0.2C/0.2C, and the test results are shown in Table 1.

As a comparison, pure silicon powder was used as the negative electrode material, and the rest were the same as above, to make a CR2025 button battery, and the number was D2, and the charge-discharge cycle test was carried out under the same test conditions. The test results are also shown in Table 1.

Table 1 Cycle performance test results

It can be seen from Table 1 that the composite negative electrode materials prepared in Examples 1-5 are used to make lithium metal batteries. After 500 cycles at a rate of 0.2C, the capacity retention rate is still more than 57%, while in Comparative Examples 1-2, Although the specific capacity of the first charge and discharge is good, after 100 cycles, the capacity retention rate is lower than 19%, which shows that the composite negative electrode material prepared in the present invention can improve the cycle performance under the premise of simple preparation method and low preparation cost. marked progress.

The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications completed under the technical spirit suggested by the present invention shall belong to This invention covers the scope of the patent.

Claims (8)

1. Si @ TiO₂The preparation method of the hollow core-shell composite material is characterized by comprising the following steps:

(1) dissolving a certain amount of silicon nanoparticles in a glucose solution, and performing ultrasonic treatment for 20-60 min to obtain a mixed solution A;

(2) transferring the mixed solution A into a hydrothermal reaction kettle, and reacting for 5-10h at the hydrothermal temperature of 150-200 ℃ to obtain a Si/C composite material precursor;

(3) dissolving the Si/C composite material precursor in a certain amount of titanium source solution, aging for 8-12h, and vacuum drying to obtain Si/C/TiO₂A precursor;

(4) mixing the Si/C/TiO₂Calcining the precursor in air for 1-4h at 500-600 ℃ to obtain Si @ TiO₂A hollow composite material.

2. Si @ TiO according to claim 1₂The preparation method of the hollow core-shell composite material is characterized by comprising the following steps: the particle size of the silicon nanoparticles is less than 100 nm.

3. Si @ TiO according to claim 1₂The preparation method of the hollow core-shell composite material is characterized in that the concentration of glucose in the glucose solution is 0.1-0.2 mol/L, and the mass ratio of the silicon nanoparticles to the glucose is 1: 5-10.

4. Si @ TiO according to claim 1₂The preparation method of the hollow core-shell composite material is characterized in that the titanium source in the step (3) is one or more of titanium tetrachloride solution, titanium sulfate solution, tetrabutyl titanate solution and titanium isopropoxide solution with the concentration of 0.1-0.2 mol/L.

5. Si @ TiO according to claim 1₂The preparation method of the hollow core-shell composite material is characterized by comprising the following steps: in the step (3), the mass ratio of the silicon nanoparticles to the solute in the titanium source is controlled to be 1: 5-10.

6. Si @ TiO according to claim 1₂The preparation method of the hollow core-shell composite material is characterized by comprising the following steps: in the step (3), the aging is performed under the stirring condition of the rotation speed of 300-500 rpm.

7. Si @ TiO prepared by any one of claims 1 to 6₂A hollow core-shell composite material.

8. Si @ TiO prepared by any one of claims 1 to 6₂The hollow core-shell composite material is applied to a silicon-based negative electrode material of a lithium ion battery.

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