Surface modification of silicon particles for electrochemical storage
Silicon particles for active materials and electro-chemical cells are provided. The active materials comprising silicon particles described herein can be utilized as an electrode material for a battery. In certain embodiments, the composite material includes greater than 0% and less than about 90% by weight silicon particles, the silicon particles having an average particle size between about 10 nm and about 40 μm, wherein the silicon particles have surface coatings comprising silicon carbide or a mixture of carbon and silicon carbide, and greater than 0% and less than about 90% by weight of one or more types of carbon phases, wherein at least one of the one or more types of carbon phases is a substantially continuous phase.
1. A method of forming a composite material film comprising:
providing a mixture comprising a precursor and silicon particles, wherein individual ones of the silicon particles comprise a surface layer including silicon monoxide (SiO), silicon dioxide (SiO 2 ), or silicon oxide (SiO x );
pyrolyzing the precursor to convert the precursor into one or more types of carbon phases; and
reacting one of the one or more types of carbon phases with the silicon monoxide (SiO), silicon dioxide (SiO 2 ), or silicon oxide (SiO x ) to form surface coatings comprising a mixture of carbon and silicon carbide on the silicon particles, whereby forming the composite material film having hard carbon as a matrix phase that is a continuous phase that extends across the entire film and the silicon carbide is between the silicon particles and the hard carbon.
2. The method of claim 1 , wherein the surface coatings form on 50% to 99% of the silicon particles.
3. The method of claim 1 , wherein the surface coatings form on 60% to 99% of the silicon particles.
4. The method of claim 1 , wherein the surface coatings form on 70% to 99% of the silicon particles.
5. The method of claim 1 , wherein the surface coatings form on substantially all of the silicon particles.
6. The method of claim 1 , wherein reacting comprises reacting the one of the one or more types of carbon phases with substantially all the silicon monoxide (SiO), silicon dioxide (SiO 2 ), or silicon oxide (SiO x ).
7. The method of claim 1 , wherein the surface coatings comprise silicon carbide and are substantially free of silicon oxide.
8. The method of claim 1 , wherein pyrolyzing the precursor comprises heating the mixture to a temperature of about 750° C. to about 1300° C.
9. The method of claim 8 , wherein pyrolyzing the precursor comprises heating the mixture to a temperature of about 800° C. to about 1200° C.
10. The method of claim 9 , wherein pyrolyzing the precursor comprises heating the mixture to a temperature of about 1175° C.
11. The method of claim 1 , further comprising:
casting the mixture on a substrate;
drying the mixture to form a film;
removing the film from the substrate; and
placing the film in a hot press.