Passivated silicon-carbon composite materials
Passivated silicon-carbon composite materials and related processes are disclosed that overcome the challenges for providing amorphous nano-sized silicon entrained within porous carbon. Compared to other, inferior materials and processes described in the prior art, the materials and processes disclosed herein find superior utility in various applications, including energy storage devices such as lithium ion batteries.
1 . A hydrosilylation passivated silicon-carbon composite material, comprising:
a) a porous carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% microporosity;
b) nano-sized silicon domains disposed within pores of the porous carbon scaffold, wherein a surface of the nano-sized silicon domains is passivated due to Si—R groups, wherein R comprises:
(i) an organic functional group comprising one or more of carbon, oxygen, nitrogen, and hydrogen; and,
(ii) one or more optional halogen element;
c) a silicon content of 30% to 60% by weight;
d) a surface area of less than 30 m 2 /g;
e) a Z of less than 10, wherein Z=1.875×[(M1100−M)/M1100]×100, wherein M1100 is a mass of the passivated silicon-carbon composite material at 1100° C. and M is the minimum mass of the passivated silicon-carbon composite material between 800° C. and 1100° C. when the passivated silicon-carbon composite material is heated under air from about 25° C. to about 1100° C., as determined by thermogravimetric analysis; and
f) a φ of greater than or equal to 0.1, wherein φ=(Max peak height dQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in a half-cell coin cell, and Regime I is 0.8V-0.4V and Regime III is 0.15V-0V,
wherein:
the surface of the nano-sized silicon domains is passivated using chemical vapor infiltration (CVI) by reacting the surface with an alkene gas or alkyne gas at a temperature ranging from 100° C. to 200° C.; and
the surface of the nano-sized silicon domains comprises Si—H surface groups that react with the alkene gas or the alkyne gas to form the Si—R groups.
2 . The composite material of claim 1 , further comprising a Dv50 between 5 nm and 20 microns.
3 . The composite material of claim 1 , wherein the hydrosilylation passivated silicon-carbon composite material gasses less than 0.005 mol/mol silicon/h in an aqueous suspension at 45° C.
4 . The composite material of claim 1 , comprising a mol ratio of oxygen to silicon, wherein the mole ratio of oxygen to silicon increases less than 0.01 mol/mol/day when exposed to 25° C. in the presence of air.
5 . The composite material of claim 1 , wherein the Si—H surface groups are formed by reacting the porous carbon scaffold with a silane gas in the presence of hydrogen.