SiO_x nanoparticles were granulated, and their microstructures and effects on electrochemical behaviors were investigated. In spite of the promising electrochemical performance of SiO_x, nanoparticles have limitations such as high surface area, low density, and difficulty in handling during slurry processing. Granulation can be one solution. In this study, pelletizing and annealing were conducted to create particles with sizes of several decades of micron. Decrease in surface area directly influences the initial charge and discharge process when granules are applied as anode materials for Li-ion batteries. Lower surface area is key to decreasing the amount of irreversible phase-formation, such as Li₂Si₂O₅, Li₂SiO₃ and LuSiO₄, as well as forming the solid electrolyte interface. Additionally, aggregation of nanoparticles is required to obtain further enhancement of the electrochemical behavior due to restrictions that there be no Li₄SiO₄-related reaction during the first discharge process.