Electrochemical Characteristics and Li+ Ion Intercalation Kinetics of Dual-phase Li4Ti5O12/Li2TiO3 Composite in Voltage Range of 0−3 V

Abstract

Li4Ti5O12, Li2TiO3 and dual-phase Li4Ti5O12/Li2TiO3 composite were prepared by sol-gel method with average particle size of 1 µm, 0.3 µm and 0.4 µm, respectively. Though Li2TiO3 is electrochemically inactive, the rate capability of Li4Ti5O12/Li2TiO3 is comparable to Li4Ti5O12 at different current rates. Li4Ti5O12/Li2TiO3 also shows good rate performance of 90 mA h g-1 at high rate of 10 C in voltage range of 1−3 V, attributable to increased interfaces in the composite. While Li4Ti5O12 delivers capacity retention of 88.6 % at 0.2 C over 50 cycles, Li4Ti5O12/Li2TiO3 exhibits no capacity fading at 0.2 C (40 cycles) and capacity retention of 98.45 % at 0.5 C (50 cycles). This highly stable cycling performance is attributed to the contribution of Li2TiO3 in preventing undesirable reaction of Li4Ti5O12 with the electrolyte during cycling. CV curves of Li4Ti5O12/Li2TiO3 in 0−3 V range exhibit two anodic peaks at 1.51 V and 0.7−0.0 V, indicating two modes of lithium intercalation into the lattice sites of active material. Owing to enhanced intercalation/de-intercalation kinetics in 0−3 V, composite electrode delivers superior rate performance of 203 mAh/g at 2.85 C and 140 mAh/g at 5.7 C with good reversible capacity retention over 100 cycles.