Effects of TiO2 phase on the performance of Li4Ti5O12 anode for lithium-ion batteries

Abstract In recent reports, doping TiO 2 phases into Li 4 Ti 5 O 12 system is an effective approach to improve the electrochemical performance of Li-titanate batteries, and the explanations of this phenomenon are mainly focused on the functions of TiO 2 phases at low current density. In this paper, through the ex-situ X-ray diffraction analysis, it is revealed that the crystal structure of rutile-TiO 2 in Li 4 Ti 5 O 12 -TiO 2 electrode is very different after cycles at high and low current density. Such results can beneficially help us have a fully understanding of Li-ion storage mechanism in multi-phase electrode. Moreover, three kinds of dual and ternary phase Li 4 Ti 5 O 12 -TiO 2 composites with the same morphology of nanosheets are fabricated and their electrochemical performances are compared for the first time. These Li 4 Ti 5 O 12 -TiO 2 composites exhibit excellent performance at high current density: Li 4 Ti 5 O 12 -rutile-anatase TiO 2 electrode delivers a reversible capacity of about 125 mA h g −1 with a total capacity decreasing less than 5% after 2000 cycles at 30 C. Li 4 Ti 5 O 12 -rutile TiO 2 nanosheets electrode tested from 1 to 50 C with 100 cycles for each rate delivers a capacity of 108 mA h g −1 at high rate of 50 C, which is 69.2% of the specific capacity at 1 C.