Anode material having a uniform metal-semiconductor alloy layer
The present invention relates to methods for producing anode materials for use in nonaqueous electrolyte secondary batteries. In the present invention, a metal-semiconductor alloy layer is formed on an anode material by contacting a portion of the anode material with a solution containing metals ions and a dissolution component. When the anode material is contacted with the solution, the dissolution component dissolves a part of the semiconductor material in the anode material and deposit the metal on the anode material. After deposition, the anode material and metal are annealed to form a uniform metal-semiconductor alloy layer. The anode material of the present invention can be in a monolithic form or a particle form. When the anode material is in a particle form, the particulate anode material can be further shaped and sintered to agglomerate the particulate anode material.
1. A method for forming an anode structure having a metal-semiconductor alloy layer, comprising the steps of:
obtaining a particulate anode material comprising a silicon or silicon alloy semiconductor material;
contacting the particulate anode material with a solution comprising metal ions and a dissolution component;
dissolving a part of the semiconductor material from the particulate anode material;
reducing the metal ions in the solution to the metal with electrons provided by the dissolution of the semiconductor material into the solution;
depositing the reduced metal on the particulate anode material to form a deposited reduced metal layer having a thickness of about 100 nanometers to about 3 micrometers;
annealing the particulate anode material to form a metal-semiconductor layer on the particulate anode material, the metal-semiconductor layer comprising an alloy of the reduced metal and the silicon or silicon alloy semiconductor material and having a thickness of about 100 nanometers to about 3 micrometers;
shaping the particulate anode material into an anode structure; and
sintering the anode structure to agglomerate the particulate anode material and form a sintered anode structure having a metal-semiconductor alloy layer.
2. The method of claim 1 , further comprising the step of etching the sintered anode structure.
3. The method of claim 1 , further comprising a step of annealing the particulate anode material and the deposited metal to form a metal-semiconductor alloy layer prior to shaping the particulate anode material.
4. The method of claim 1 , wherein a metal ion solution containing the metal ions and a displacement solution containing the dissolution component are pre-mixed to form the solution comprising the metal ions and the dissolution component before contacting the anode material.
5. The method of claim 4 , wherein the semiconductor material is silicon, the metal is nickel, and the dissolution component is fluoride.
6. The method of claim 4 , wherein the pre-mixed solution comprises about 0.02 to 0.5 M Ni 2+ and about 0.5 to 5 M fluoride.
7. The method of claim 4 , wherein the pre-mixed solution comprises about 0.02 to 0.5 M Ni 2+ and about 0.5 to 5 M peroxide.
8. The method of claim 4 , wherein the premixed solution is between about 50-98° C. during the contacting step.
9. The method of claim 4 , wherein the premixed solution has a pH between about 6 and 11.
10. The method of claim 1 , wherein the semiconductor is silicon.
11. The method of claim 1 , wherein the dissolution component is fluoride, chloride, peroxide, hydroxide, or permanganate.
12. The method of claim 11 , wherein the dissolution component is fluoride, or hydroxide.
13. The method of claim 1 , wherein the metal is a noble metal.
14. The method of claim 1 , wherein the metal is a base metal.
15. The method of claim 1 , wherein the metal is nickel.
16. The method of claim 1 wherein the particulate anode material is annealed to form a metal-semiconductor layer on the particulate anode material before the particulate anode material is sintered.
17. The method of claim 1 wherein the particulate anode material is annealed to form a metal-semiconductor layer on the particulate anode material before the particulate anode material is shaped to form the anode structure.
18. The method of claim 1 wherein the particulate anode material is annealed to form a metal-semiconductor layer on the particulate anode material after the particulate anode material is shaped to form the anode structure.
19. The method of claim 1 wherein the semiconductor material is silicon, the metal is nickel, the metal-semiconductor alloy is nickel silicide and the particulate anode material is annealed to form a metal-semiconductor layer on the particulate anode material before the particulate anode material is sintered.
20. The method of claim 1 wherein the particulate anode material is annealed at a temperature of about 500° C. to form the metal-semiconductor layer on the particulate anode material.
21. The method of claim 1 wherein the anode structure is sintered at a temperature of about 1,000° C.