High Lithium Insertion Voltage Single-Crystal H 2 Ti 12 O 25 Nanorods as a High-Capacity and High-Rate Lithium-Ion Battery Anode Material.

H2 Ti12 O25 holds great promise as a high-voltage anode material for advanced lithium-ion battery applications. To enhance its electrochemical performance, control of the crystal orientation and morphology is an effective way to cope with slow Li+ -ion diffusion inside H2 Ti12 O25 with severe anisotropy. In this report, Na2 Ti6 O13 nanorods, prepared from Na2 CO3 and anatase TiO2 in molten NaCl medium, were used as a precursor in the synthesis of long single-crystal H2 Ti12 O25 nanorods with reactive facets. The as-prepared H2 Ti12 O25 nanorods with a diameter of 100-200 nm showed higher charge (extraction) specific capacity and better rate performance than previously reported systems. The reversible capacity of H2 Ti12 O25 was 219.8 mAh g-1 at 1C after 100 cycles, 172.1 mAh g-1 at 10C, and 144.4 mAh g-1 at 20C after 200 cycles; these values are higher than those of H2 Ti12 O25 prepared by the conventional soft-chemical method. Moreover, the as-prepared H2 Ti12 O25 nanorods exhibited superior cycle stability with more than 94 % retention of capacity with nearly 100 % coulombic efficiency after 100 cycles at 1C. On the basis of the above results, long single-crystal H2 Ti12 O25 nanorods synthesized in molten NaCl with outstanding electrochemical characteristics hold a significant amount of promise for hybrid electric vehicles and energy-storage systems.