# US 10,246,337 B2 · Safe and low temperature thermite reaction systems and method to form porous silicon

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- Number: US 10,246,337 B2
- Document ID: US10246337B2
- Status: Granted
- Kind: B2
- Application number: 15/436,027
- Filed: 2017-02-17
- Published: 2018-08-23
- Granted: 2019-04-02
- Earliest claimed: 2017-02-17
- Assignees: Battelle Memorial Institute
- Applicants: Battelle Memorial Institute
- Inventors: Xiaolin Li; Ji-Guang Zhang; Jun Liu
- Web page: https://patentgrep.com/patent/US10246337B2

## CPC

- C01B 33/023: by reduction of silica or {free} silica-containing material
- C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram
- C01P 2004/03: obtained by SEM
- C01P 2004/04: obtained by TEM, STEM, STM or AFM
- C01P 2006/12: Surface area
- C01P 2006/40: Electric properties
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

Embodiments of a safe, low-temperature reaction system and method for preparing porous silicon are disclosed. The porous silicon is prepared from porous silica, a low-melting metal halide, and a metal comprising aluminum, magnesium, or a combination thereof. Advantageously, embodiments of the disclosed methods can be performed at temperatures ≤400° C. Silicon produced by the disclosed methods has a porosity that is equal to or greater than the porous silica precursor. The porous silicon is suitable for use in electrodes.

## Claims

### Claim 1

A method for preparing porous silicon, comprising:
forming a mixture comprising (i) porous silica, (ii) a metal comprising aluminum, magnesium, or a combination thereof, and (iii) a metal halide comprising a metal M, where the metal M is Ti, Zn, Ga, Ge, Aq, Sn, Sb, Au, Hq, Tl, Bi, or a combination thereof, and the metal halide has a melting point ≤400° C.;
heating the mixture in a sealed vessel at a temperature greater than or equal to the melting point of the metal halide and ≤400° C. under an inert atmosphere to form a product comprising porous silicon; and
combining the product with acid to remove any by-products from the porous silicon.

### Claim 2 (depends on 1)

The method of claim 1, wherein the metal M is Zn, Sn, Sb, Ti, or a combination thereof.

### Claim 3 (depends on 1)

The method of claim 1, wherein the metal halide is a metal chloride, metal bromide, metal iodide, or a combination thereof.

### Claim 4 (depends on 1)

The method of claim 1, wherein the metal halide is a metal chloride.

### Claim 5 (depends on 4)

The method of claim 4, wherein the metal chloride is ZnCl2, SnCl2, SbCl3, TiCl4, or a combination thereof.

### Claim 6 (depends on 4)

The method of claim 4, wherein the metal chloride is ZnCl2, SnCl2, or SbCl3, and the mixture is heated at a temperature within a range of from 250° C. to 350° C.

### Claim 7 (depends on 1)

The method of claim 1, wherein the mixture is heated for a period of time within a range of from one hour to 24 hours to form the porous silicon.

### Claim 8 (depends on 1)

The method of claim 1, wherein the acid is hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, or a combination thereof.

### Claim 9 (depends on 1)

The method of claim 1, wherein the porous silica, the metal comprising aluminum, magnesium, or a combination thereof, and the metal halide comprising the metal M are combined in a molar ratio of 1 mole silica, 2-6 moles metal, and 1-6 moles metal halide.

### Claim 10 (depends on 1)

The method of claim 1, wherein the porous silica has an initial Brunauer-Emmett Teller (BET) surface area as determined by nitrogen adsorption and the porous silicon has a BET surface area within a range of 1.0-1.8X the initial BET surface area of the porous silica.

### Claim 11

A method for preparing porous silicon, comprising:
forming a mixture comprising (i) porous silica, (ii) a metal comprising aluminum, magnesium, or a combination thereof, and (iii) an iron halide having a melting point ≤400° C.;
heating the mixture in a sealed vessel at a temperature greater than or equal to the melting point of the iron halide and ≤400° C. under an inert atmosphere to form a product comprising porous silicon; and
combining the product with acid to remove any by-products from the porous silicon, wherein the porous silica, the metal comprising aluminum, magnesium, or a combination thereof, and the iron halide are combined in a molar ratio of 1 mole silica, 2-6 moles metal, and 0.2-0.3 moles iron halide.

### Claim 12 (depends on 11)

The method of claim 11, wherein the iron halide is FeCl3.