High rate capability and long-term cyclability of Li4Ti4.9V0.1O12 as anode material in lithium ion battery

Li₄Ti_4.9V_0.1O₁₂ nanometric powders were synthesized via a facile solid-state reaction method under inert atmosphere. XRD analyses demonstrated that the V-ions successfully entered the structure of cubic spinel-type Li₄Ti₅O₁₂ (LTO), reduced the lattice parameter and no impurities appeared. Compared with the pristine LTO, the electronic conductivity of Li₄Ti_4.9V_0.1O₁₂ powders is as high as 2.9 × 10⁻¹ S cm⁻¹, which should be attributed to the transformation of some Ti³⁺ from Ti⁴⁺ induced by the efficient V-ions doping and the deficient oxygen condition. Meanwhile, the results of XPS and EDS further proved the coexistence of V⁵⁺ and Ti³⁺ ions. This mixed Ti⁴⁺/Ti³⁺ ions can remarkably improve its cycle stability at high discharge–charge rates because of the enhancement of the electronic conductivity. The images of SEM showed that Li₄Ti_4.9V_0.1O₁₂ powders have smaller particles and narrower particle size distribution under 330 nm. And EIS indicates that Li₄Ti_4.9V_0.1O₁₂ has a faster lithium-ion diffusivity than LTO. Between 1.0 and 2.5 V, the electrochemical performance, especially at high rates, is excellent. The discharge capacities are as high as 166 mAh g⁻¹ at 0.5C and 117.3 mAh g⁻¹ at 5C. At the rate of 2C, it exhibits a long-term cyclability, retaining over 97.9% of its initial discharge capacity beyond 1713 cycles. These outstanding electrochemical performances should be ascribed to its nanometric particle size and high conductivity (both electron and lithium ion). Therefore, the as-prepared material is promising for such extensive applications as plug-in hybrid electric vehicles and electric vehicles.