A high-energy ball-milling process was used for the solid-state synthesis of single phase powders of spinel-structured lithium-titanium oxide (Li4Ti5O12). The influence of the high-energy ball-milling time on the structure, morphology, and electrochemical performance of synthesized powders was investigated. Remarkably, the electrochemical tests performed at high rates showed significantly improved specific capacity of the powders obtained with extended synthesis times. In particular, after 50 charging/discharging cycles at the current rate of 1C, the samples retained more than 94% of their initial specific capacity.