Substantially enhanced rate capability of lithium storage in Na₂Ti₆O₁₃ with self-doping and carbon-coating

Na₂Ti₆O₁₃ (NTO) has recently been reported for lithium ion storage and showed very promising results. In this work, we report substantially enhanced rate capability in NTO nanowires by Ti(iii) self-doping and carbon-coating. Ti(iii) doping and carbon coating were found to work in synergy to increase the electrochemical performances of the material. For 300 cycles at 1C (1C = 200 mA g^-1) the charge capacity of the electrode is 206 mA h g^-1, much higher than that (89 mA h g^-1) of the pristine NTO electrode. For 500 cycles at 5C the electrode can still deliver a charge capacity of 180.5 mA h g^-1 with a high coulombic efficiency of 99%. At 20C the capacity of the electrode is 2.6 times that of the pristine NTO. These results clearly demonstrate that the Ti(iii) self-doping and uniform carbon coating significantly enhanced the kinetic processes in the NTO nanowire crystal, making it possible for fast charge and discharge in Li-ion batteries.