High capacity silicon nitride-based composite anodes for lithium ion batteries

Abstract

A new composite material comprised of Si nitride (SiN_x) derived from Si nanoparticles (SiNPs) via a vacuum CVD approach within a graphene matrix was synthesized as a potential Li ion battery (LIB) anode material. The deposition technique generated an external composition of Si₃N₄ and SiN_0.73 on the SiNP, with the overall N-levels increasing with deposition time. The SiN_x electrochemical reaction can be attributed to a two-stage reversible mechanism: first the SiN_x phase was converted to a matrix of Li₃N with embedded nano Si, and then the Si content participates in the high capacity alloying/dealloying reactions. Galvanostatic cycling of the composite (50% Si w/w) using 500 mA g⁻¹ displayed exceptionally stable capacity around 1400 mA h g⁻¹ attributed to the improved stress management and conductivity of the Li₃N matrix. SiN_x is demonstrated to be a compelling anode for LIBs, and with further development and optimization this might become the leading contender for the high capacity anode to possibly succeed current graphitic electrodes.