Effects of post-treatments on the electrochemical properties of solid-state reacted Li^sub 4^Ti^sub 5^O^sub 12^--high energy milling and annealing

This study is designed and performed to verify whether nano-sized Li^sub 4^Ti^sub 5^O^sub 12^ particles can be acquired by simple high energy milling from the economic solid-state reacted coarse powder for high power lithium ion battery applications. For this, Li^sub 4^Ti^sub 5^O^sub 12^ is synthesized by heat treatment at 800 and 850°C for 3 h using Li^sub 2^CO3 and TiO2, followed by high energy milling. Even though a comparable particle size to that of expensive wet chemical methods, or even a smaller particle size of 25 nm, can be acquired by 5 h of milling, the electrochemical properties of the particles are found to be deteriorated due to the decrease in Li^sub 4^Ti^sub 5^O^sub 12^ crystallinity associated with the milling. On the other hand, a subsequent annealing at 750°C for the milled powder is shown to recover both the capacity and rate capability of the anode electrode owing to the increased crystallinity, indicating the importance of particle crystallinity besides a fine particle size for the enhanced electrochemical properties for high power applications.[PUBLICATION ABSTRACT]