Electrochemical properties of nano-sized Li₄Ti₅O₁₂ powders prepared by flame spray pyrolysis

Nanosized Li₄Ti₅O₁₂ powders are prepared from a spray solution with a 15 % excess of lithium using a flame spray pyrolysis process. The mean particle size of the precursor powders is 23 nm. The Li₄Ti₅O₁₂ powders obtained after post-treatment at 700°C have small amounts of rutile TiO2 impurities and have a mean particle size of 47 nm. Post-treatment at 800°C, however, produces phase-pure Li₄Ti₅O₁₂ powders with a mean particle size of 300 nm. The initial discharge capacities of the Li₄Ti₅O₁₂ powders are 132, 160, and 151 mAh g-1 for post-treatment temperatures of 600, 700, and 800°C, respectively, and the Coulombic efficiencies are 87 %, 92 %, and 99 %. The hard aggregation between the particles and growth of the particles to submicron sizes that occur at a high post-treatment temperature of 800°C make a large proportion of the Li₄Ti₅O₁₂ grains inactive, lowering the specific capacity. The discharge capacities of the powders post-treated at 700°C decrease from 160 to 157 mAh g^-1 over 50 cycles, and the capacity retention is 98 %.