Silicon Nitride Encapsulated Silicon Nanocrystals for Lithium Ion Batteries

Abstract

Silicon nitride (SiNx) is a promising passivation material for Si nanocrystal (NC)‐based anodes in lithium‐ion batteries. We report a single‐step plasma synthesis process for growing SiNx‐encapsulated Si NCs. In this process, nucleation and growth of the Si NCs occurred in the upstream region of a continuous‐flow tubular plasma reactor via dissociation and polymerization of SiH4 diluted in Ar. The Si NC surface was nitrided downstream via N2 injection into the plasma afterglow. Infrared spectra show a N‐rich SiNx coating, with some SiSi surface bonds that remained intact with no N insertion. Photoluminescence spectra show a Si NC core with an average diameter of ∼4 nm. These SiNx‐coated Si NCs remained susceptible to oxidation in the ambient, which reduced the Si core by approximately a monolayer. Optical emission spectra from the downstream glow region show that excited N2 species likely led to surface Si nitridation.