composites, which can be attributed to high grain boundary density, abundant phase interfaces and in situ formed carbon, for storing extra lithium ions, enhancing rapid lithium insertion/extraction kinetics and improving electron transport rate.
Corresponding
14As is well known, the volumic capacity is an important parameter for the practical application of Li 4 Ti 5 O 12 -based materials 37,38 . The capacities of the samples in this work are addressed not only by weight dimensionality (mAh g -1 ) but also by volume (mAh cm -3 ). The densities of the pure composites are calculated to be 3.41, 2.97, 3.52 and 3.26 g cm -3 , respectively. The initial three charge-discharge cycle profiles for pure composite electrodes with a current rate of 0. 5 C (1 C= 175 mA g -1 ) are shown in Fig 7a-d. Agree well with the result of CV curves (Fig. 6), two long flat plateaus at about 1.51 and 1.62 V are observed for all the samples due to the typical lithium insertion/extraction processes of Li 4 Ti 5 O 12 . Moreover, the voltage plateaus at around 1.98 and 1.72 V are verified as the lithium ion insertion/extraction reaction of anatase TiO 2 . 5 The initial discharge capacities of pure composites are 134, 157, 144 and 170 mAh g −1 , corresponding to 455, 466, 506 and 554 mAh cm -3 , respectively. The charge-discharge profiles of all samples are nearly invariable after the second cycle. The reversible capacities of the third cycle for pure composites are approximately 87, 119, 117 and 143 mAh g −1 , corresponding to 297, 353, 411 and 466 mAh cm -3 , respectively.The higher specific capacity of Li 4 Ti 5 O 12 /TiO 2 /C composite is contributed by relatively high theoretical capacity of anatase TiO 2 and carbon, and the extra lithium storage derived from phase interfaces.