Silicon Nitride Coated Silicon Thin Films As Anodes for Li-Ion Batteries

Abstract

When using silicon in anodes for Li-ion batteries, there is a tradeoff between using small silicon structures to avoid cracking and having small surface area to reduce electrolyte degradation due to an unstable Solid Electrolyte Interface (SEI). To facilitate the growth of a stable and thin SEI, we propose to coat silicon with a thin layer of silicon nitride. Silicon nitride by itself has been determined to function as a conversion electrode material, forming lithium nitride and elemental silicon during the initial lithiation. Using a thin film model system, we demonstrate the effect of using nitride coatings with different stoichiometry on the cyclability and high rate capacity of the electrodes. The results show that a nitride coating has a positive effect on both the cycling stability and high rate performance.