Methods of forming composite material films
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 of silicon particles. The silicon particles have an average particle size between about 0.1 μm and about 30 μm and a surface including nanometer-sized features. The composite material also includes greater than 0% and less than about 90% by weight of one or more types of carbon phases. 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, the method comprising:
providing a mixture comprising polyimide or a polyimide precursor, the mixture further comprising silicon particles and graphite particles; and
pyrolysing the mixture to convert the polyimide or the polyimide precursor into one or more carbon phases to form the composite material film such that the one or more carbon phases comprises hard carbon that is 10% to 25% by weight of the composite material film and holds together the pyrolysed film, and the silicon particles are between 50% and 90% by weight of the composite material film distributed throughout the one or more carbon phases, wherein after pyrolysing the mixture, the mixture forms a self-supported composite structure.
2. The method of claim 1 , further comprising:
casting the mixture on a substrate;
drying the mixture;
removing the dried mixture from the substrate; and
placing the dried mixture in a hot press.
3. The method of claim 1 , further comprising forming a battery electrode from the composite material film.
4. The method of claim 1 , wherein providing the mixture comprises providing silicon particles having an average largest dimension of 10 nm to 40 μm.
5. The method of claim 1 , wherein providing the mixture comprises providing conductive particles in the mixture.
6. The method of claim 1 , wherein providing the mixture comprises providing copper, nickel, or stainless steel particles in the mixture.
7. The method of claim 1 , wherein the composite material film comprises more than 60% by weight silicon particles.
8. The method of claim 7 , wherein the composite material film comprises 60% to 80% by weight silicon particles.
9. The method of claim 8 , wherein the composite material film comprises 70% to 80% by weight silicon particles.
10. The method of claim 1 , wherein the composite material film comprises 5% to 15% by weight graphite particles.
11. The method of claim 10 , wherein the composite material film comprises 10.5% by weight graphite particles.
12. The method of claim 1 , wherein the composite material film is electrochemically active.
13. The method of claim 1 , wherein at least one of the carbon phases is electrochemically active and electrically conductive.
14. The method of claim 1 , wherein at least one of the carbon phases is a continuous phase.