Hydrogenation synthesis of blue TiO₂ for high-performance lithium-ion batteries

Blue hydrogenated rutile TiO₂ nanoparticles (blue TiO ₂) are prepared by treating white rutile via an enhanced hydrogenation process (i.e., high pressure and temperature). The materials characterization results demonstrate that the hydrogenation process leads to the increase in the unit cell volume and decrease in the size compared with the untreated white TiO₂. The electrochemical impedance spectra analyses and theoretical energy calculations using density functional theory (DFT) suggest that the hydrogenation process not only improves electronic conductivity due to the formation of oxygen vacancy in the hydrogenation process but also dramatically augments lithium-ion mass transport within the crystalline lattice due to the introduction of oxygen vacancy and crystalline dislocation. Because of these characteristics resulting from the hydrogenation process, the blue TiO₂ based lithium ion batteries (LIBs) possess significantly higher energy capacity and better rate performance than the white TiO₂ based LIBs. In particular, at the rate of 0.1 and 5 C (1 C = 336 mAh g^-1), the discharge capacities of the blue rutile are maintained at ca.179.8 and 129.2 mAh g^-1, while the capacities of the white TiO₂ are just ca. 119.6 and 55.5 mAh g^-1, respectively.