The development of a method for synthesizing granulated silicon oxide nanoparticles (SiOx NPG) via a thermal plasma and water granulation process and determination of the optimum stoichiometry of silicon oxide (SiOx) for achieving high electrochemical performance of an anode based on the developed material are presented herein. The structure of the SiOx NPGs was confirmed by means of X-ray fluorescence, transmission electron microscopy, and X-ray diffraction. A high initial capacity of similar to 1196 mA h g(-1) was achieved using the fabricated SiOx anode with x similar to 1.06, giving rise to a Coulombic efficiency of 75% after the first cycle. Further combination of SiOx with graphite (3wt%) for use as an anode gave rise to high capacity (397 mA center dot h center dot g(-1)) and a very high Coulombic efficiency of 99.99% after 200 cycles. The physical properties of the synthesized materials were investigated based on micrometric analysis. On the basis of the volume expansion and cycle capacity, the optimal oxygen ratio of SiOx was determined to be x similar to 1.06. (C) 2014 Elsevier Ltd. All rights reserved.