High throughput production of nanocomposite SiO_<i>x</i>powders by plasma spray physical vapor deposition for negative electrode of lithium ion batteries

Abstract

Nanocomposite Si/SiO _<i>x</i> powders were produced by plasma spray physical vapor deposition (PS-PVD) at a material throughput of 480 g h^-1. The powders are fundamentally an aggregate of primary ∼20 nm particles, which are composed of a crystalline Si core and SiO _<i>x</i> shell structure. This is made possible by complete evaporation of raw SiO powders and subsequent rapid condensation of high temperature SiO _<i>x</i> vapors, followed by disproportionation reaction of nucleated SiO _<i>x</i> nanoparticles. When CH₄ was additionally introduced to the PS-PVD, the volume of the core Si increases while reducing potentially the SiO _<i>x</i> shell thickness as a result of the enhanced SiO reduction, although an unfavorable SiC phase emerges when the C/Si molar ratio is greater than 1. As a result of the increased amount of Si active material and reduced source for irreversible capacity, half-cell batteries made of PS-PVD powders with C/Si = 0.25 have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAh g^-1 after 100 cycles at the same time.