CN-122003383-A - Method for producing porous silicon

Abstract

A method of making porous silicon comprising providing magnesium silicide with silica nanoparticles and silica microparticles, or by providing magnesium with silica nanoparticles and silica microparticles. Either mixture is then heated to a temperature of up to 500 ℃.

Inventors

• M.YAN
• S. Patvadan

Assignees

• 谢菲尔德大学

Dates

Publication Date

20260508

Application Date

20241001

Priority Date

20231011

Claims (15)

1. 1. A method of making porous silicon comprising: providing magnesium silicide with silica nanoparticles and silica microparticles, and The mixture is heated at a temperature of up to 500 ℃.
2. 2. The method of claim 1, further comprising forming magnesium silicide by: Providing magnesium and silica particles, and The mixture is heated at a temperature of up to 500 ℃.
3. 3. A method of making porous silicon comprising: providing magnesium and silica nanoparticles and silica microparticles, and The mixture is heated at a temperature of up to 500 ℃.
4. 4. The method according to any of the preceding claims, wherein the silica nanoparticles have a size in the range of 1 nm to 75 nm, and preferably less than 20 nm.
5. 5. The method of any of the preceding claims, wherein the silica microparticles range in size from 1 micron to 1000 microns.
6. 6. The method according to any one of the preceding claims, wherein the ratio of silica nanoparticles to silica microparticles is in the range of 10:90 to 80:20, preferably 20:80 to 50:50, still more preferably wherein the ratio is 25:75.
7. 7. The method of claim 2 and any of claims 4 to 6 when dependent on claim 2, wherein the method of claim 2 is performed immediately prior to the method of claim 1 or simultaneously with the method of claim 1.
8. 8. The method of claim 1 or any of claims 4 to 6 when not dependent on claim 2, wherein the method of claim 2 is conducted remotely from the method of claim 1.
9. 9. A method according to any one of the preceding claims, wherein the mixture is heated to a temperature of up to 450 ℃ or preferably up to 380 ℃.
10. 10. The method of claim 1 or claim 9, wherein the mixture is heated to a target temperature at a rate of 1 ℃ per minute, and optionally wherein the mixture is maintained at the target temperature for up to 6 hours.
11. 11. The method of any of the preceding claims, wherein the method further comprises forming a battery anode from the porous silicon.
12. 12. The method according to any one of the preceding claims, wherein the silica nanoparticles and silica microparticles originate from any one of or a combination of precipitated silica, silica gel, particulate silica, custom produced silica including organic silica and/or bio-inspired silica, sand, rice hulls, crushed glass, silicate or mixtures thereof.
13. 13. The method of any of the preceding claims, wherein the porous silicon has a specific surface area in the range of 100 to 235 m 2 /g.
14. 14. The method of any of the preceding claims, wherein the porous silicon has a total pore volume in the range of 0.2 to 0.6 cm 3 /g.
15. 15. The method of any of the preceding claims, wherein the weight ratio of magnesium silicide to the total weight of silica nanoparticles and silica microparticles is 1:1.

Description

Method for producing porous silicon Technical Field The present invention relates to a method of manufacturing porous silicon. Background Silicon has great potential as a negative electrode material for lithium ion batteries because it has a high specific capacity and, for example, can store approximately 10 times more charge than graphite currently conventionally selected as a negative electrode for batteries. One problem with silicon is that it exhibits a large volume expansion, which can cause problems in the limited space of the cell, possibly leading to cell swelling and damage. This can be alleviated by using porous silicon, which provides void volumes into which silicon can expand. Currently, mass production of porous silicon is achieved by magnesian reduction (reduction in the presence of magnesium). However, this process requires high temperatures in excess of 650 ℃ to achieve meaningful yields. Furthermore, performing the magnesia reduction at such temperatures results in a loss of the desired porosity due to sintering of the silicon during the process. Disclosure of Invention According to a first aspect of the present disclosure there is provided a method of manufacturing porous silicon comprising providing magnesium silicide with silica nanoparticles and silica microparticles and then heating the mixture at a temperature of up to 500 ℃. Heating the mixture to a temperature of up to 500 ℃ is a less energy consuming process than known processes, thereby reducing the cost and severity of the manufacturing process. Optionally, the method further comprises forming magnesium silicide by providing magnesium and silica particles and heating the mixture at a temperature of up to 500 ℃. In this case, the manufacturing process can be considered a "one-pot process" without the need for multiple additions of reactants, thereby shortening and simplifying manufacturing. Alternatively, according to a second aspect of the present disclosure, a method of making porous silicon includes providing magnesium with silica nanoparticles and silica microparticles and heating the mixture at a temperature of up to 500 ℃. Suitably, the silica nanoparticles have a size in the range 1 nm to 75 nm, and preferably less than 20 nm. The silica nanoparticles act as promoters of the larger particle reaction, such as, but not limited to, by acting as an initiator of the reaction. Preferably, the size of the silica microparticles is in the range of 1 micron to 1000 microns. The inclusion of larger particles ensures that the mixture exhibits improved handling properties, as the larger particles are less likely to disperse or fly away and keep the smaller silica nanoparticles in place prior to reaction. The larger particles also ensure the presence of void spaces, thus ensuring a porous end product. Suitably, the ratio of silica nanoparticles to silica microparticles is in the range of from 10:90 to 80:20, preferably 20:80 to 50:50, still more preferably wherein the ratio is 25:75. These ranges provide a mixture that has the ease of handling of larger particles while retaining sufficient nanoparticles to allow the reaction to proceed successfully below 500 ℃. Alternatively, the magnesium silicide may be formed by providing magnesium and silica particles and heating the mixture at up to 500 ℃ either immediately prior to or simultaneously with the process for making porous silicon. The process may be performed as a continuous process in which the magnesium silicide is formed prior to the manufacture of the porous silicon, or the process may be performed in discrete batches in which the magnesium silicide is formed simultaneously with the manufacture of the porous silicon. Alternatively, the formation of magnesium silicide may be carried out remotely from the method of making porous silicon by providing magnesium with silica particles and heating the mixture at up to 500 ℃. Thus, magnesium silicide may be purchased or manufactured remotely from the method of manufacturing porous silicon. The production of magnesium silicide may be optimized independently of or isolated from the production of porous silicon. Suitably, the mixture is heated to a temperature of up to 450 ℃ or preferably up to 380 ℃. Further lowering the reaction temperature from 500 ℃ enhances the energy saving benefits, making the process more cost effective. Optionally, wherein the mixture is heated to the target temperature at a rate of 1 ℃ per minute. Preferably, the mixture is maintained at the target temperature for a maximum of 6 hours. Suitably, the method further comprises forming the battery anode from porous silicon. Thus, the large volume expansion of silicon in the cell (which can lead to cell swelling and damage) is alleviated by the use of porous silicon, which provides void volume into which silicon can expand. Preferably, the silica nanoparticles and silica microparticles are derived from any one of, or a combination of, precipitated silica, silica gel, part