CN114566639A

CN114566639A - SiO (silicon dioxide)x/C composite material and preparation method and application thereof

Info

Publication number: CN114566639A
Application number: CN202210050883.1A
Authority: CN
Inventors: 吴正颖; 惠学文; 陈志刚; 钱君超; 查振龙; 邢凯
Original assignee: Suzhou University of Science and Technology
Current assignee: Suzhou University of Science and Technology
Priority date: 2022-01-17
Filing date: 2022-01-17
Publication date: 2022-05-31
Anticipated expiration: 2042-01-17
Also published as: CN114566639B

Abstract

The invention relates to the technical field of new materials, in particular to SiO_xa/C composite material, a preparation method and application thereof. SiO of the invention_xthe/C nano composite material takes plant leaves existing in large quantity in nature as a structure guiding agent and a carbon source, and the sub-oxide SiO of nano silicon is reduced by infiltration, high-temperature heat treatment and ball-milling magnesiothermic reduction_xAnd co-assembling with biochar. Biological tissues are used as templates, materials with various shapes can be prepared, and the preparation method has the characteristics of low cost, renewable raw materials and the like. The resulting SiO_xWhen the/C nano composite material is used as a lithium ion negative electrode material, the current density is 100 mA.g^‑1Current density of 794mAh g still remained after circulating for 150 cycles^‑1High specific capacity of (2). The biochar formed in situ is Li⁺And electrons provide a rapidly migrating crosslinked network while buffering the volume expansion of the electrode material during cyclingSo that the material has excellent lithium storage performance.

Description

SiO (silicon dioxide)xComposite material/C and preparation thereofMethod and use

Technical Field

The invention relates to the technical field of new materials, in particular to SiO_xa/C composite material, a preparation method and application thereof.

Background

In recent years, silicon sub-oxide (SiO)_x) The material has reasonable Li intercalation⁺Electric potential up to 2500mAh g^-1And that during lithiation silicate and Li are formed which effectively buffer the volume expansion₂O, is becoming an important research object for lithium ion battery negative electrode materials. Of course, SiO_xWhen the material is used for the lithium ion battery cathode material, inherent defects such as poor conductivity, low coulombic efficiency of the first circle, unstable cycle performance caused by volume expansion in the charging and discharging process and the like exist. Therefore, the SiO still has the prior SiO for improving the stability and the conductivity of the material_xThe research of the anode material is hot. Mixing SiO_xNanocrystallization, compositing with carbon (C) materials or modification by doping with other elements are common strategies. Wherein SiO is mixed with_xCompounding with C to be reinforced SiO_xOne of the most effective methods for electrochemical performance of the base anode material.

Mixing SiO_xCo-assembly of nanoparticles with C-matrix or coating of SiO with C-layer_xThe nano particles can construct a special composite structure and greatly improve SiO_xMainly due to the unique advantages of C when used for electrochemical energy storage: (1) the C material generally has good conductivity, and can promote the rapid migration of electrons and promote the reaction kinetics; (2) compared with inorganic carrier (such as tin-based oxide glass, ITO) with rigid crystal structure, the C material has certain elasticity in structure and can buffer SiO_xThe stress and deformation generated by the material in the cyclic charge-discharge process can keep the material with good integrity and difficult inactivation; (3) the material C has wide sources and simple preparation, and has application prospect of large-scale production; (4) the presence of C may promote more stable SEI film formation during battery charging and discharging.

Although the SiO can be greatly improved by being assembled with the C material_xOf materialsElectrochemical performance, but how to obtain SiO by a simple and efficient method_xthe/C composite remains a challenging scientific problem. On the other hand, the nature forms a colorful biological tissue structure in the process of continuous evolution. Biological tissues are used as templates, and various materials with special structures and diversified forms can be obtained by adopting a bionic construction mode; in addition, the biological template also has the characteristics of low cost, reproducibility and the like. Therefore, the cell tissue of natural plant is used as a structure-oriented template and a carbon source, a silicon source is introduced into a biological template, and the silicon source is converted into SiO_xSimultaneously, the plant template is converted into biological carbon, so that SiO is hopefully obtained_xa/C composite material.

Disclosure of Invention

The invention provides SiO_xThe preparation method of the/C composite material comprises the following steps:

s1, soaking the pretreated biological template in a silicon source solution, washing, drying, and calcining in an inert atmosphere to obtain a sample SiO₂/C；

S2, SiO the sample₂Mixing the magnesium powder and the sodium chloride according to a certain proportion, and performing ball milling under an inert gas atmosphere according to a certain ball-to-material ratio to obtain a mixture;

s3, removing impurities from the mixture to obtain the SiO_xa/C composite material.

Preferably, the biological template is one or more of cabbage leaves, lettuce leaves and camellia petals.

Preferably, in step S1, the pretreatment is performed by soaking in an aqueous solution of ethanol; the volume concentration of ethanol in the ethanol water solution is 50-95%, and the pH value is 1-2; the soaking time is 2-4 weeks.

Preferably, the solvent of the silicon source solution is ethanol, and the mass concentration of the silicon source is 15-75%; the silicon source is one or more of methyl orthosilicate, tetrabutyl orthosilicate and tetraethyl orthosilicate.

Preferably, in the step S1, the soaking time is 48-72 h.

Preferably, in the step S1, the calcination temperature is 600-800 ℃, and the calcination time is 1-5 h.

Preferably, in the step S2, magnesium powder, sodium chloride and the sample SiO are mixed₂The mass ratio of C/C is 0.5-0.8: 0.8-1.2: 1.

preferably, in the step S2, the ball-milling ratio of balls to materials is 15-30: 1; the rotation speed of the ball milling is 150-.

Preferably, in the step S3, the step of removing impurities includes adding dilute acid into the mixture, reacting for 12-36h to remove magnesium powder and its oxide, adding hydrofluoric acid, and reacting to remove SiO₂Then filtering and vacuum drying; the dilute acid is dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid.

The invention also provides SiO_xa/C composite material.

The invention also provides the SiO_xThe application of the/C composite material in preparing the negative electrode material of the lithium battery.

Compared with the prior art, the technical scheme of the invention has the following advantages:

biological tissues are used as templates, materials with various shapes can be prepared, and the preparation method has the characteristics of low cost, renewable raw materials, sustainability and the like. The composite material prepared by the invention can form SiO in situ₂Composite structure of/C, so that the final SiO_xThe nanoparticles are highly dispersed in the porous carbon. At the same time, at 100mA · g^-1Current density of 794mAh g still remains after 150 cycles^-1The capacity of (c). The carbon matrix in the composite material is Li⁺And electrons provide a rapidly migrating crosslinked network while buffering the SiO_xThe volume of the/C electrode material expands in the circulation process, so that the stability of the material is improved.

Drawings

FIG. 1 is SiO in comparative example 1₂SEM image of/C composite material.

FIG. 2 shows SiO in example 1_xSEM image of/C composite material.

FIG. 3 shows SiO synthesized in example 1_xTEM images of the/C composite material at different scales; wherein a is 500 nm; b is 20 nm.

FIG. 4 shows SiO synthesized in example 1_xcomposite/C, SiO synthesized in comparative example 1₂XRD pattern of/C material.

FIG. 5 shows SiO synthesized in example 1_xcomposite/C, SiO synthesized in comparative example 1₂Rate performance graph of/C material, bio-C material synthesized in comparative example 2.

FIG. 6 shows SiO synthesized in example 1_xcomposite/C, SiO synthesized in comparative example 1₂Cycle performance profiles for/C material, comparative example 2 synthetic bioc material.

FIG. 7 shows SiO synthesized in example 2_xA rate performance graph of the/C composite material.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Example 1

SiO (silicon dioxide)_xThe preparation method of the/C composite material comprises the following steps:

(1) washing fresh caulis et folium Brassicae Capitatae with deionized water, and soaking in ethanol solution for two weeks (vEtOH: H)₂O is 1: the acidity of the solution was adjusted by adding HCl until pH 2) was reached to remove pigments and soluble organic matter in the plant cells. And then, cleaning the pretreated cabbage and naturally drying for later use.

(2) Pre-treating cabbage at a concentration of 0.45 mol. L^-1Is immersed in a solution of tetraethyl orthosilicate (TEOS) in ethanol for 72 h. Subsequently, the leaves were washed with deionized water, air dried, and then N at 800 deg.C₂Roasting for 2 hours in the atmosphere, and naming the treated sample as SiO₂/C-045。

(3) Mixing SiO₂Mixing the/C-045, magnesium powder and sodium chloride in a mass ratio of 1:0.64:1, and then sealing the mixture together into a ball milling tank in a ball-to-feed ratio of 30:1 stainless steel balls under an argon atmosphere. The magnesium hot ball milling reduction is carried out for 2h at the rotating speed of 300 rpm.

(4) The ball milled mixture was treated with 2M HCl12h, then 1mLHF was added to the solution to remove unreacted SiO₂. Filtering and vacuum drying to obtain SiO material_xa/C-045 composite material.

Example 2

(1) Washing fresh caulis et folium Brassicae Capitatae with deionized water, and soaking in ethanol solution for two weeks (vEtOH: H)₂O1: 1, the acidity of the solution was adjusted by adding HCl until pH 2) was reached to remove pigments and soluble organic matter in the plant cells. And then, cleaning the pretreated cabbage and naturally drying the cabbage for later use.

(2) Pre-treating cabbage at a concentration of 0.6 mol. L^-1Is immersed for 72 hours in an ethanol solution of tetraethyl orthosilicate (TEOS). Subsequently, the leaves were washed with deionized water, air dried, and then N at 800 deg.C₂Roasting for 2 hours in the atmosphere, and naming the treated sample as SiO₂/C-060。

(3) Mixing SiO₂C-060 was mixed with magnesium powder and sodium chloride in a mass ratio of 1:0.64:1, and then the mixture was sealed together into a ball mill pot under an argon atmosphere with stainless steel balls in a ball to feed ratio of 30: 1. The magnesium hot ball milling reduction is carried out for 2h at the rotating speed of 300 rpm.

(4) The ball milled mixture was treated with 2M HCl for 12h, then 1mLHF was added to the solution to remove unreacted SiO₂. Filtering and vacuum drying to obtain SiO material_xa/C-060 composite material.

Comparative example 1

(1) Washing fresh caulis et folium Brassicae Capitatae with deionized water, and soaking in ethanol solution for two weeks (vEtOH: H)₂O1: 1, the acidity of the solution was adjusted by adding HCl until pH 2) was reached to remove pigments and soluble organic matter in the plant cells. And then, cleaning the pretreated cabbage and naturally drying for later use.

(2) Pre-treating cabbage at a concentration of 0.45 mol. L^-1Is immersed in a solution of tetraethyl orthosilicate (TEOS) in ethanol for 72 h. Subsequently, the leaves were washed with deionized water, air dried, and then N at 800 deg.C₂Roasting for 2 hours in the atmosphere, and treating and collecting the material which is SiO₂/C-045。

Comparative example 2

(1) Purchasing fresh cabbage, washing with deionized water to remove surface dust. Soaking caulis et folium Brassicae Capitatae in ethanol water solution for two weeks (V)_EtOH:V_H2O1:1) to remove cabbage pigments and other organic matter.

(2) And cleaning the pretreated cabbage leaves with deionized water for 3 times and then drying.

(3) Placing the dried cabbage leaves in a tube furnace in N₂Calcining for 2h at 800 ℃ under the atmosphere. Sampling, grinding and collecting to obtain the material C.

Effect evaluation 1

FIG. 1 is SiO comparative example 1₂C-045 and SiO from example 1_xSEM image of/C-045 (FIG. 2) composite. As can be clearly seen from FIG. 1, SiO₂the/C-045 composite material not only keeps the morphology of the biological template, but also has a smooth surface, which indicates that SiO₂Uniformly assembled on the cabbage-derived carbon material. As can be seen from FIG. 2, the SiO generated by the ball-milling magnesiothermic reduction_xThe macro morphology of the/C-045 material is micron-sized small particles.

FIG. 3 shows SiO synthesized in example 1_xTEM images of the/C composite at different magnifications. Graph a shows 500nm scale; b is 20 nm. From the lower magnification TEM image (FIG. 3a), it can be seen that SiO_xthe/C composite material exhibits a uniform, lamellar shape. In the high resolution TEM picture (FIG. 3b), a large amount of uniformly dispersed nano SiO can be observed_xThe size of the particles and the nano particles is about 4.8 nm.

FIG. 4 shows SiO obtained in example 1_xSiO obtained in C-045 and comparative example 1₂XRD pattern of/C-045 material. SiO 2₂The diffraction peak of/C-045 at about 23 ℃ corresponds to amorphous SiO₂And biochar. Ball-milled magnesium heated SiO_xthe/C-045 exhibits two peaks at 23 ℃ and 44 ℃ which correspond to the amorphous component and the partially crystallized component of the composite.

FIG. 5 shows SiO synthesized in example 1_xAnd the rate performance graph obtained by assembling the/C-045 composite material into the lithium ion half cell. When the current density is from 50mA g^-1Increased to 500mA g^-1The discharge capacity of the material is reduced (from 911mA · g)^-1Change to 447mA g^-1). And SiO obtained in comparative example 1 before the magnesium thermal reduction₂the/C-045 material always shows a specific SiO ratio_xthe/C-045 composite material has a lower discharge capacity and the capacity fade increases as the current density increases. Simultaneously, SiO before and after reduction₂C-045 and SiO_xBoth of the/C-045 discharge capacities were much higher than those of the biochar sample synthesized in comparative example 2 without silicon oxide. Although the discharge capacity of the biochar is basically stable under different current densities, the discharge capacity is always very low (270-174 mA g)^-1)。

FIG. 6 shows SiO synthesized in example 1_xThe cycle performance diagram of the lithium ion half-cell assembled by the/C-045 composite material is that the first 10 circles are low current density (50 mA. g)^-1) The following activation process. SiO 2_xthe/C-045 composite material shows very stable long-cycle charge and discharge performance, and the discharge capacity is always stable at 790mAh g^-1The capacity retention rate was 63.0%. While unreduced SiO₂The discharge capacity of/C-045 (comparative example 1) decays very significantly as the cycle progresses, as measured by 790mAh g after activation^-1Quickly decays to 290mAh g^-1. The long cycle performance of the biochar obtained in comparative example 2 was always stable, but the discharge capacity was very low (290mAh g)^-1)。

FIG. 7 shows SiO synthesized in example 2_xAnd the/C-060 composite material is assembled into a rate performance graph of the lithium ion half cell. As can be seen from the figure, SiO obtained by increasing the concentration of the silicon source during the synthesis_xDischarge performance of/C composite material and SiO_xPer C-045 close to 794mAh g at low current density^-1. The discharge capacity was attenuated by the increase of the current density, and when the current density was again recovered to 50mA g^-1In the process, the material still retains 794 mAh.g^-1The discharge capacity of (2).

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims

1. SiO (silicon dioxide)_xThe preparation method of the/C composite material is characterized by comprising the following steps:

s1, soaking the pretreated biological template in a silicon source solution, and calcining in an inert atmosphere to obtain a sample SiO₂/C；

S2, SiO the sample₂Mixing the magnesium powder and sodium chloride, and performing ball milling in an inert gas atmosphere to obtain a mixture;

2. The method of claim 1, wherein the biological template is one or more of cabbage leaves, lettuce leaves, and camellia petals.

3. The method according to claim 1, wherein in the step S1, the pretreatment is soaking in an aqueous ethanol solution; the soaking time is 2-4 weeks.

4. The method according to claim 1, wherein the silicon source solution has a concentration of 15 to 75 wt% and the solvent is ethanol; the silicon source is one or more of methyl orthosilicate, tetrabutyl orthosilicate and tetraethyl orthosilicate.

5. The method as claimed in claim 1, wherein the soaking time in step S1 is 48-72 h.

6. The method as claimed in claim 1, wherein the calcination temperature in step S1 is 600-800 ℃ and the calcination time is 1-5 h.

7. The method according to claim 1, wherein in step S2, magnesium powder, sodium chloride and the sample SiO₂The mass ratio of C/C is 0.5-0.8: 0.8-1.2: 1.

8. the preparation method according to claim 1, wherein in the step S3, the specific operation of removing impurities is as follows: adding dilute acid into the mixture, reacting for 12-36h to remove magnesium powder and its oxide, adding hydrofluoric acid, reacting to remove SiO₂Then filtering and vacuum drying; the dilute acid is dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid.

9. SiO obtainable by a process according to any one of claims 1 to 8_xa/C composite material.

10. SiO as claimed in claim 9_xThe application of the/C composite material in preparing the negative electrode material of the lithium battery.