Soft-Chemical Synthesis and Electrochemical Property of H2Ti12O25 as a Negative Electrode Material for Rechargeable Lithium-Ion Batteries

Upon heating the as-prepared H 2 Ti 3 O 7 sample, single-phase samples of H 2 Ti 6 O 13 , H 2 Ti 12 O 25 and TiO 2 (B) were prepared with different heating conditions; at 120°C for 48 h in a vacuum of 20 Pa for H 2 Ti 6 O 13 , at 260°C for 5 h in air for H 2 Ti 12 O 25 , and at 350°C for 5 h in air for TiO 2 (B). The chemical compositions of these compounds were determined by the DTA-TG and ICP analyses. The coordination environments around hydrogen atoms in these compounds were examined by using FTIR and 1 H-MAS-NMR data. The reversible Li insertion and extraction reactions around 1.5–1.6 V with initial intercalation capacities of 283 and 236 mAh g −1 , were observed for H 2 Ti 6 O 13 and H 2 Ti 12 O 25 , respectively. The structural changes upon cycling were clarified for H 2 Ti 3 O 7 and TiO 2 (B). Among the four compounds, H 2 Ti 12 O 25 showed superior cycling performance with the discharge capacity retention rate of 96% after 50 cycles. H 2 Ti 12 O 25 is suggested to be one of the promising high-voltage oxide negative electrodes in advanced lithium-ion batteries.