AU2020101794A4 - A method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction - Google Patents
A method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/023—Preparation by reduction of silica or free silica-containing material
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- C—CHEMISTRY; METALLURGY
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- C—CHEMISTRY; METALLURGY
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- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention discloses a method for reducing nano-silica by
molten-salt-mediated magnesiothermic reduction, which comprises the following
steps: (1) weighing nano-silica, magnesium powder, sodium chloride and potassium
chloride, respectively, grinding and mixing uniformly to obtain product A; (2) placing
product A in a graphite boat, then placing the graphite boat in a tubular furnace and
heating, and taking out the substance on the graphite boat after cooling to obtain
product B; (3) pouring product B into deionized water for rinsing, and then pouring it
into hydrochloric acid solution for rinsing, followed by successively washing with
water and ethanol, and performing suction filtration to obtain product C; and (4)
drying product C to obtain nanometer silicon. The invention has the beneficial effects
of high reduction yield, high purity, simple process and suitability for large-scale
production.
10
1/2
A
ASi
-10 0 10 20 30 40 50 60 70 80 90 100
20(degree)
Fig.1
200 nm EHIT =20.00 kV Signal A =SE2 Date :26 Apr 2019
WD 8.6 mm Mag = 40.00 K X Time :5:32:02
Fig. 2
Description
1/2
ASi
-10 0 10 20 30 40 50 60 70 80 90 100 20(degree)
Fig.1
200 nm EHIT =20.00 kV Signal A =SE2 Date :26 Apr 2019 WD 8.6 mm Mag = 40.00 K X Time :5:32:02
Fig. 2
A method for reducing nano-silica by molten-salt-mediated
magnesiothermic reduction
The present invention relates to a method for reducing nano-silica by
magnesiothermy, in particular to a method for reducing nano-silica by
magnesiothermy added with molten salts.
BACKGROUND OF INVENTION With the rapid development of science and technology and increased use of
electronic equipments, the demand for chemical power source is increasing.
Lithium-ion batteries are widely used because of their advantages such as small size,
easy portability, high specific charge/discharge capacity, and stability. Graphite, as a
traditional cathode material for lithium-ion batteries, can no longer meet the growing
commercial demand for its relatively low specific capacity, which limits the
promotion of lithium-ion batteries. Therefore, the development of anode materials for
lithium-ion batteries with high stability, high specific capacity, high charge-discharge
efficiency, high cycle performance, stable discharge platform and lower cost has
become a mainstream trend.
In the study of anode materials for lithium-ion batteries, silicon-based
materials have a higher theoretical specific capacity and are safe with no pollution,
and therefore have attracted much attention. However, the silicon on the market is not
high in purity and large in size, so it is difficult to meet the requirements of cathode
materials for lithium-ion batteries. Therefore, it is particularly important to prepare a
silicon material with small size and high purity.
A magnesiothermic reduction method is a low-cost and scalable process for preparing silicon materials. Since 2007, various silicon nanostructures, including nanocrystals, nanotubes, nanowires, and the like, have been made by reducing different silicon sources via the magnesiothermic reduction method. However, as the magnesiothermic reduction process is a spontaneous exothermic reaction, the local temperature reaches 1941C in the experimental process, which far exceeds heating temperature, resulting in excessive growth of silicon grains and difficulty in obtaining nano-silicon materials.
The object of the present invention is to provide a method for reducing
nano-silica by molten-salt-mediated magnesiothermic reduction. The invention has
the characteristics of high reduction yield, high purity, simple process and is suitable
for large-scale production.
The technical solution of the invention lies in a method for reducing
nano-silica by molten-salt-mediated magnesiothermic reduction, which comprises the
following steps:
(1) weighing nano-silica, magnesium powder, sodium chloride and potassium
chloride, respectively, grinding and mixing uniformly to obtain product A;
(2) placing product A in a graphite boat, then placing the graphite boat in a
tubular furnace and heating, and taking out the substance on the graphite boat after
cooling to obtain product B;
(3) pouring product B into deionized water for rinsing, and then pouring it
into hydrochloric acid solution for rinsing, followed by successively washing with
water and ethanol, and performing suction filtration to obtain product C; and
(4) drying product C to obtain nano-silica.
In step (1) of the above-described method for reducing nano-silica by
molten-salt-mediated magnesiothermic reduction, the mass ratio of nano-silica,
magnesium powder, sodium chloride and potassium chloride is 1:1:1:1.
In step (2) of the above-described method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction, placing the graphite boat in a tubular furnace and heating specifically comprises introducing argon gas after placing the graphite boat in a tubular furnace, heating to 800°C with a heating rate of 5°C
/min, and keeping at 800°C for 3h.
In step (3) of the above-described method for reducing nano-silica by
molten-salt-mediated magnesiothermic reduction, the concentration of the
hydrochloric acid solution is 0.5-1.5mol/L.
In step (3) of the above-described method for reducing nano-silica by
molten-salt-mediated magnesiothermic reduction, pouring product B into deionized
water for rinsing is to remove the molten salts.
In step (3) of the above-described method for reducing nano-silica by
molten-salt-mediated magnesiothermic reduction, pouring it into hydrochloric acid
solution for rinsing is to remove excess byproducts.
In step (4) of the above-described method for reducing nano-silica by
molten-salt-mediated magnesiothermic reduction, the drying temperature is 50-70°C
and the drying time is 10-12h.
The present invention has the following beneficial effects over the prior art.
1) In the present invention, nano-silica, magnesium powder, sodium chloride
and potassium chloride which are weighted, respectively, with a mass ratio of 1: 1:1:1,
are ground, so that the reaction is more complete. Oxygen is isolated by heating and
reducing in an argon atmosphere, and the temperature is kept at 800°C, thereby
facilitating progress of the reaction. The molten salts are removed by rinsing in
deionized water, the excess byproducts are removed by rinsing in the hydrochloric
acid solution, and the excess impurity is removed by successively washing with water
and ethanol, thereby improving the purity of nanometer silicon.
2) The reduction of nano-silica by the existing magnesiothermic reduction
method will cause excessive growth of silicon grains, which in turn results in
relatively low reduction rate and purity. In the present invention, sodium chloride and
potassium chloride binary salts (molten salts) are added as endothermic agents to absorb heat released from the magnesiothermic reduction process, thereby preventing excessive growth of silicon grains and improving the yield and purity of reduction.
3) The first delithiation specific capacity of the nanometer silicon material
obtained by magnesiothermic reduction of the present invention can reach 3527
mAh-g-1 , whereas the first delithiation specific capacity of the nano-silicon material
obtained by the magnesiothermic reduction method without adding molten salts can
only reach 1934 mAh-g-1, indicating that the method of the present invention can
improve the purity of reduction. In addition, the yield of nano-silica reduced by means
of the method of the present application can be up to 82%, and the method of the
present application is simple, low in cost, and suitable for large-scale production.
The experiments demonstrate the following.
The following experiments on the nanometer silicon prepared in the
Examples of the present invention were carried out.
1. All the characteristic peaks of the XRD pattern (as shown in FIG.1) of the
nanometer silicon of the present invention can be completely overlapped with silicon,
demonstrating that the product obtained by reduction is crystalline silicon.
2. Numerous small particles can be seen from the scanning electron
microscope (SEM) image (as shown in FIG.2) of nanometer silicon of the present
invention, and the sizes of the particles are nanoscale.
3. It can be seen from the comparison diagram (as shown in FIG.3) of the
first delithiation specific capacity of nanometer silicon of the present invention and
that of nanometer silicon obtained by reduction without adding molten salts that the
first delithiation specific capacity of the battery after adding molten salts can reach
3527 mAh-g- 1, whereas that of the battery without adding molten salts can only reach
1934 mAh-g- 1, indicating that the purity of reduction after adding molten salts is
higher.
In summary, the present invention has the beneficial effects of high reduction
yield, high purity, simple process, and suitability for large-scale production.
FIG.1 is an X-ray diffraction (XRD) pattern of nanometer silicon of the
present invention.
FIG.2 is a scanning electron microscope (SEM) image of nanometer silicon
of the present invention.
FIG.3 is a comparison diagram of the first delithiation specific capacity of
nanometer silicon of the present invention and that of nanometer silicon obtained by
reduction without adding molten salts.
The present invention will be further described in connection with the
appended Drawings and the Examples, which are not as a basis for limiting the
invention.
Example 1
A method for reducing nano-silica by molten-salt-mediated magnesiothermic
reduction comprised the following steps:
(1) weighing 10 g nano-silica, 10 g magnesium powder, 10 g sodium chloride
and 10 g potassium chloride, respectively, grinding and mixing uniformly to obtain
product A;
(2) placing product A in a graphite boat, then placing the graphite boat in a
tubular furnace, introducing argon gas into the tubular furnace, heating to 8000 C with
a heating rate of 50 C/min, and keeping at 800 0C for 3h, and taking out the substance
on the graphite boat after cooling to obtain product B;
(3) pouring product B into deionized water for rinsing, and then pouring it
into 0.5mol/L hydrochloric acid solution for rinsing 12h, followed by successively
washing with water and ethanol, and performing suction filtration to obtain product C;
and
(4) drying product C at a temperature of 50°C for 10h to obtain nanometer
silicon.
Example 2
A method for reducing nano-silica by molten-salt-mediated magnesiothermic
reduction comprised the following steps:
(1) weighing 8 g nano-silica, 8 g magnesium powder, 8 g sodium chloride
and 8 g potassium chloride, respectively, grinding and mixing uniformly to obtain
product A;
(2) placing product A in a graphite boat, then placing it in a tubular furnace,
introducing argon gas into the tubular furnace, heating to 800°C with a heating rate of
°C/min, and keeping at 800°C for 3h, and taking out the substance on the graphite
boat after cooling to obtain product B;
(3) pouring product B into deionized water for rinsing, and then pouring it
into 1mol/L hydrochloric acid solution for rinsing 12h, followed by successively
washing with water and ethanol, and performing suction filtration to obtain product C;
and
(4) drying product C at a temperature of 60°C for lh to obtain nanometer
silicon.
Example 3
A method for reducing nano-silica by molten-salt-mediated magnesiothermic
reduction comprised the following steps:
(1) weighing 15 g nano-silica, 15 g magnesium powder, 15 g sodium chloride
and 15 g potassium chloride, respectively, grinding and mixing uniformly to obtain
product A;
(2) placing product A in a graphite boat, then placing the graphite boat in a
tubular furnace, introducing argon gas into the tubular furnace, heating to 8000 C with
a heating rate of 50 C/min, and keeping at 800 0 C for 3h, and taking out the substance on the graphite boat after cooling to obtain product B;
(3) pouring product B into deionized water for rinsing, and then pouring it
into 1.5mol/L hydrochloric acid solution for rinsing 12h, followed by successively
washing with water and ethanol, and performing suction filtration to obtain product C;
and
(4) drying product C at a temperature of 70°C for 12h to obtain nanometer
silicon.
Claims (5)
1. A method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction, characterized in that the method comprises the following steps: (1) weighing nano-silica, magnesium powder, sodium chloride and potassium chloride, respectively, grinding and mixing uniformly to obtain product A; (2) placing product A in a graphite boat, then placing the graphite boat in a tubular furnace and heating, and taking out the substance on the graphite boat after cooling to obtain product B; (3) pouring product B into deionized water for rinsing, and then pouring it into hydrochloric acid solution for rinsing, followed by successively washing with water and ethanol, and performing suction filtration to obtain product C; and (4) drying product C to obtain nanometer silicon.
2. The method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction according to claim 1, characterized in that in step (1), the mass ratio of nano-silica, magnesium powder, sodium chloride and potassium chloride is 1:1:1:1.
3. The method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction according to claim 1, characterized in that in step (2), placing the graphite boat in a tubular furnace and heating comprises introducing argon gas after placing graphite boat in a tubular furnace, heating to 800°C with a heating rate of 5°C /min, and keeping at 800°C for 3h.
4. The method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction according to claim 1, characterized in that in step (3), the concentration of the hydrochloric acid solution is 0.5-1.5mol/L.
5. The method for reducing nano-silica by molten-salt-mediated magnesiothermic reduction according to claim 1, characterized in that in step (4), the drying temperature is 50-70°C and the drying time is 10-12h.
Applications Claiming Priority (2)
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|---|---|---|---|
| CN201910809605.8 | 2019-08-29 | ||
| CN201910809605.8A CN110371982A (en) | 2019-08-29 | 2019-08-29 | A kind of method of fused salt magnesium reduction process reduced nano silica |
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Cited By (3)
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| CN115196645A (en) * | 2022-08-20 | 2022-10-18 | 山西工程技术学院 | Preparation method of boron arsenide powder |
| CN115845902A (en) * | 2022-12-08 | 2023-03-28 | 上海交通大学深圳研究院 | Graphite phase carbon nitride photocatalytic material and preparation method thereof |
| CN117230459A (en) * | 2023-11-13 | 2023-12-15 | 中国科学院广州地球化学研究所 | In-situ preparation method and device of silicon-based nano-micron material |
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| CN111960423A (en) * | 2020-08-28 | 2020-11-20 | 广东工业大学 | Nano hollow porous silicon material and preparation method and application thereof |
| CN112850716A (en) * | 2021-02-04 | 2021-05-28 | 昆明理工大学 | Method for preparing nano-scale porous crystal Si by magnesiothermic reduction |
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| CN108666560A (en) * | 2018-05-15 | 2018-10-16 | 欣旺达电子股份有限公司 | Lithium ion battery, nano silicon material and preparation method thereof |
| CN109694075B (en) * | 2018-12-18 | 2021-02-23 | 安徽工业大学 | Low-temperature ball-milling nano silicon powder, preparation method and application |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115196645A (en) * | 2022-08-20 | 2022-10-18 | 山西工程技术学院 | Preparation method of boron arsenide powder |
| CN115845902A (en) * | 2022-12-08 | 2023-03-28 | 上海交通大学深圳研究院 | Graphite phase carbon nitride photocatalytic material and preparation method thereof |
| CN117230459A (en) * | 2023-11-13 | 2023-12-15 | 中国科学院广州地球化学研究所 | In-situ preparation method and device of silicon-based nano-micron material |
| CN117230459B (en) * | 2023-11-13 | 2024-02-13 | 中国科学院广州地球化学研究所 | In-situ preparation method and device of silicon-based nano-micron material |
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