TiN-coated micron-sized tantalum-doped Li4Ti5O12 with enhanced anodic performance for lithium-ion batteries

Micron-sized Li4Ti5O12 with both surface modification (TiN) and inner Ta5+ doping has been synthesized via a combination of solid-state reaction and surface thermal nitridation. The physical and chemical properties of all samples are tested systematically. The results demonstrate that tantalum is successfully doped in the lattice of Li4Ti5O12 and a thin amorphous TiN coated on the surface of the Li4Ti5O12 particles. The TiN coating layer enhances surface electronic conductivity and electrical contact between particles, while Ta5+ bulk doping in the lattice improves the intrinsic ionic conductivity and electronic conductivity inside particles. Being used as anode materials for lithium-ion batteries, the co-doped Li4Ti5O12 electrode shows much better electrochemical performance (144.5 mAh g−1 at 5 C after 500 cycles with a capacity retention of 91.63%) than that of pristine Li4Ti5O12 and mono tantalum doped or TiN coated Li4Ti5O12, only Ta-doped Li4Ti5O12 delivers 112.1 mAh g−1 at 5 C after 500 cycles and the TiN-coated Li4Ti5O12 electrode only retains 122.6 mAh g−1 at 5 C after 500 cycles. This design by exploring both surface modification and bulk doping is highly attractive for high performance Li4Ti5O12 manufacturing and may be applicative to other micron-sized electrode materials with inferior conductivity.