Synthesis of lithium insertion material Li₄Ti₅O₁₂ from rutile TiO₂ via surface activation

The synthesis of spinel-type lithium titanate, Li₄Ti₅O₁₂, a promising anode material of secondary lithium-ion battery, from "inert" rutile TiO₂, is investigated. On the purpose of increasing the reactivity of rutile TiO₂, it is treated by concentrated HNO₃. By applying such activated rutile TiO₂ as the titanium source in combination with the cellulose-assisted combustion synthesis, phase-pure Li₄Ti₅O₁₂ is successfully synthesized at 800 °C, at least 150 °C lower than that based on solid-state reaction. The resulted oxide shows a reversible discharge capacity of ∼175 mAh g^-1 at 1 C rate, near the theoretical value. The resulted oxide also shows promising high rate performance with a discharge capacity of ∼100 mAh g^-1 at 10 C rate and high cycling stability.