Europium modified TiO2 as a high-rate long-cycle life anode material for lithium-ion batteries.

Europium-modified TiO₂ with different valence states was prepared by a hydrothermal method and calcined in air. Microscopic analyses revealed that the average particle size of europium-modified TiO₂ nanoparticles is approximately 11.03 nm, and the particle size distribution is narrow. In addition, defects were introduced into TiO₂ by doping with europium. X-ray photoelectron spectroscopy (XPS) showed different valence states of Eu³⁺/Eu²⁺ in Ti_1−xEu_xO₂ (x = 0.04). A mechanism for europium-modified TiO₂ with different valence states is proposed. Europium-modified TiO₂ features excellent rate performance and long-term stability. The discharge capacity of Ti_1−xEu_xO₂ (x = 0.04) reached 417.5 mA h g⁻¹ at the initial cycle and retained 219.1 mA h g⁻¹ at 5C after 600 cycles. When it is cycled at 50C, the rate discharge capacity is maintained at 134.9 mA h g⁻¹. The electronic conductivity of TiO₂ was significantly improved by doping with different valence states of europium (Eu³⁺/Eu²⁺) due to the existence of mixed valence states of Ti⁴⁺/Ti³⁺. [ABSTRACT FROM AUTHOR]