A facile, template-free route using supercritical methanol for the preparation of hierarchical mesoporous Li4Ti5O12 spinel microspheres in a very short reaction time is introduced. Nanosized, primary Li4Ti5O12 particles (5–10 nm) are loosely aggregated and form micron-sized, secondary mesoporous spheres (0.2–2.0 μm) with a pore size of 2–10 nm. Subsequent calcination of the as-synthesized Li4Ti5O12 at a low temperature of 600 °C results in excellent long-term cyclability and high rate performance. The discharge capacity after 400 cycles at 1 C is 134.9 mAh g−1 (77.6% of the initial discharge capacity), and the discharge capacity at 10 C is 108.5 mAh g−1. The formation mechanism of hierarchical mesoporous microspheres in supercritical methanol is discussed.