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

Highlights: → Higher electronic conductivity of Li4Ti4.9V0.1O12 is 2.9 x 10-1 S cm-1. → Smaller particles and narrower particle size distribution of Li4Ti4.9V0.1O12. → XPS demonstrates the existence of Ti3+ and V5+ ions in Li4Ti4.9V0.1O12. → Li4Ti4.9V0.1O12 has more excellent electrochemical performance. - Abstract: Li4Ti4.9V0.1O12 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 Li4Ti4.9V0.1O12 powders is as high as 2.9 x 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 Li4Ti4.9V0.1O12 powders have smaller particles and narrower particle size distribution under 330 nm. And EIS indicates that Li4Ti4.9V0.1O12 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.