System and method for electrorefining of silicon

Patent metadata

Field	Value
Publication number	US-10072345-B2
Application number	US-201414551747-A
Country	US
Kind code	B2
Filing date	Nov 24, 2014
Priority date	Jun 27, 2012
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

The present disclosure provides methods and systems for electrorefining high-purity materials, for example, silicon. An exemplary system includes at least one cathode, an anode, and a reference electrode. At least one controller, for example a potentiostat, is used to control the potential difference between a reference electrode and a cathode or anode. The system can be operated in a single phase or multiple phase operation to produce high-purity materials, such as solar-grade silicon.

First claim

The invention claimed is:

1. A method for electrorefining of silicon, the method comprising:
applying a first electrical potential to a silicon-containing anode with respect to a reference electrode and a first electrical current between the anode and a first cathode to cause silicon to dissolve from the anode into a molten electrolyte and to cause silicon to deposit from the molten electrolyte onto the first cathode, the molten electrolyte coupling the anode, the first cathode, and the reference electrode;
decoupling the anode from the molten electrolyte;
coupling a second cathode to the molten electrolyte; and
applying a second electrical potential to the second cathode with respect to the reference electrode and a second electrical current between the first cathode and the second cathode to cause silicon to dissolve from the first cathode into the molten electrolyte to cause silicon to deposit from the molten electrolyte directly onto the second cathode.

2. The method of claim 1 , wherein the first electrical potential and the second electrical potential are different.

3. The method of claim 1 , wherein the second electrical potential is between: (i) the reduction potential of silicon at a process temperature, and (ii) 1.0 volts more negative than the reduction potential of silicon at the process temperature.

4. The method of claim 3 , wherein the process temperature is between 600 degrees Celsius and 1500 degrees Celsius.

5. The method of claim 1 , wherein the silicon deposited onto the second cathode has purity in excess of 99,9999%.

6. The method of claim 1 , wherein the silicon deposited onto the second cathode has a higher purity than the silicon deposited on the first cathode.

7. The method of claim 1 , wherein the electrolyte comprises at least one of calcium chloride (CaCl 2 ), lithium flouride (LiF), or lithium chloride (LiCl).

8. The method of claim 1 , wherein at least one of the first electrical potential or the second electrical potential is controlled by a potentiostat.

9. The method of claim 1 , wherein the anode comprises metallurgical grade silicon.

10. The method of claim 1 , wherein the reference electrode comprises at least one of glassy carbon or platinum.

11. The method of claim 1 , wherein the applying the first electrical potential extends for a period of time between three hours and three days.

Assignees

• Tao Meng
• Univ Arizona State

Inventors

• Tao Meng

Classifications

• C25C1/02 Primary

  of light metals · CPC title

• Y02E10/546

  Polycrystalline silicon PV cells · CPC title

• C01B33/037 Primary

  Purification (by zone-melting C30B13/00) · CPC title

• C25C7/00 Primary

  Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells (for the production of aluminium C25C3/06 - C25C3/22) · CPC title

• C25B1/006

  Chemistry & Metallurgy · mapped topic