Stabilized porous silicon structure for highly stable silicon anode and methods of making
Stabilized porous silicon particles are disclosed. The particles include a porous silicon particle comprising a plurality of interconnected silicon nanoparticles and (i) a heterogeneous layer comprising a discontinuous SiC coating that is discontinuous across a portion of pore surfaces and across a portion of an outer surface of the porous silicon particle, and a continuous carbon coating that covers outer surfaces of the discontinuous SiC coating, and remaining portions of the pore surfaces and the outer surface of the porous silicon particle, or (ii) a continuous carbon coating on surfaces of the porous silicon particle, including the outer surface and pore surfaces. Methods of making the stabilized porous silicon particles also are disclosed.
1. A method for making carbon/silicon carbide-coated porous silicon particles, comprising:
(a) providing porous silicon particles having H-terminated surface Si atoms;
(b) combining the porous silicon particles with carbon-containing precursor molecules to provide a mixture of the porous silicon particles and carbon-containing precursor molecules, wherein the carbon-containing precursor molecules surround outer surfaces of the porous silicon particles and are infiltrated into pores of the porous silicon particles;
(c) heating the mixture at a temperature of 120° C. to 350° C. for a time of 10 minutes to 10 hours to break H—Si bonds of a portion of the H-terminated surface Si atoms to provide non-H-terminated surface Si atoms and form bonds between the non-H-terminated surface Si atoms and carbon atoms of some of the carbon-containing precursor molecules, thereby forming intermediate particles comprising Si-carbon-containing precursor moieties and unreacted carbon-containing precursor molecules surrounding the porous silicon particles and infiltrated into the pores; and
(d) heating the intermediate particles at a temperature ≥400° C. for a time of ≥5 minutes to form SiC from the Si-carbon-containing precursor moieties and carbonize the remaining unreacted carbon-containing precursors, thereby forming particles comprising a porous silicon particle and a heterogeneous layer on the porous silicon particle, the heterogeneous layer comprising a discontinuous SiC coating that is discontinuous across a portion of pore surfaces and across a portion of an outer surface of the porous silicon particle, and a continuous carbon coating that covers (i) outer surfaces of the SiC coating and (ii) remaining portions of the pore surfaces and the outer surface of the porous silicon particle, thereby forming C/SiC-coated porous silicon particles.
2. The method of claim 1 , wherein the temperature and time of step (c) are insufficient to form SiC or carbonize the unreacted carbon-containing precursors.
3. The method of claim 1 , wherein the temperature and time of step (c) break the H—Si bonds of from 20-90% of the H-terminated surface Si atoms to provide non-H-terminated surface Si atoms and form bonds between the non-H-terminated surface Si atoms and carbon atoms of some of the carbon-containing precursor molecules.
4. The method of claim 1 , wherein steps (b) and (c) are performed simultaneously.
5. The method of claim 1 , wherein the carbon-containing precursor comprises an unsaturated hydrocarbon.
6. The method of claim 1 , wherein the carbon-containing precursor comprises an aromatic alkyne, an aliphatic alkyne, an aromatic alkene, an aliphatic alkene, a polymer comprising at least one unsaturated carbon-carbon bond, or any combination thereof.
7. The method of claim 1 , wherein the carbon-containing precursor comprises pitch, phenylacetylene, acetylene, ethylene, or any combination thereof.
8. The method of claim 1 , further comprising:
subsequently contacting the C/SiC-coated porous silicon particles with a subsequent carbon-containing precursor; and
subjecting the C/SiC-coated porous silicon particles to a temperature >400° C. for a time ≥5 minutes to decompose the subsequent carbon-containing precursor, thereby forming an additional carbon coating on at least a portion of an outer surface of the C/SiC-coated porous silicon particles.
9. The method of claim 1 , wherein combining the porous silicon particles with the carbon-containing precursor comprises:
infiltrating a liquid carbon-containing precursor into the porous silicon particles; or
infiltrating a solution comprising the carbon-containing precursor and an organic solvent into the porous silicon particles and subsequently evaporating the organic solvent; or
mechanically mixing the porous silicon particles with the carbon-containing precursor; or
infiltrating a vapor comprising the carbon-containing precursor into the porous silicon particles.
10. The method of claim 1 , wherein the intermediate particles are heated at 400° C. to 1000° C. for 5 minutes to 5 hours.
11. The method of claim 8 , wherein the C/SiC-coated porous silicon particles are subjected to a temperature of 600° C. to 800° C. for a time of 5 minutes to 3 hours.