High Lithium Insertion Voltage Single-Crystal H₂ Ti₁₂ O₂₅ Nanorods as a High-Capacity and High-Rate Lithium-Ion...

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.