Although Li4Ti5O12 (LTO) is considered as a promising anode material for high-power Li-ion batteries with high safety, the sluggish Li-ion diffusion coefficient restricts its widespread application. In this work, oxygen vacancy was successfully incorporated into LTO by an eco-friendly and cost-effective plasma process. The deficient LTO delivers much higher capacities of 173.4 mAh g-1 at 1C rate after 100 cycles and 140.5 mAh g-1 at 5C after 1000 cycles than those of pristine LTO. Meanwhile, even at a high rate of 20C, it displays an ultrahigh capacity of 133.1 mAh g-1 after 500 cycles with a Coulombic efficiency of 100%. Detailed analysis reveals that the lithium storage mechanisms in the oxygen-deficient LTO, especially at high rate, were dominated by the insertion behavior and dual-phase conversion due to the fast ion-diffusion ability, rather than the widely reported surface capacitance by other approaches. This work highlights that defect generation by plasma in nanomaterials is an effective way to promote ion mobility, especially at high rates, and thus can be extended to other electrode materials for advanced energy-storage applications.
Keywords: Li-ion battery; Li-ion diffusion coefficient; Li4Ti5O12; oxygen vacancy; plasma.