Synthesis, structure and electrochemical Li insertion behaviour of Li2Ti6O13 with the Na2Ti6O13 tunnel-structure

Li2Ti6O13 has been prepared from Na2Ti6O13 by Li ion exchange in molten LiNO3 at 325 °C. Chemical analysis and powder X-ray diffraction study of the reaction product respectively indicate that total Na/Li exchange takes place and the Ti–O framework of the Na2Ti6O13 parent structure is kept under those experimental conditions. Therefore, Li2Ti6O13 has been obtained with the mentioned parent structure. An important change is that particle size is decreased significantly which is favoring lithium insertion. Electrochemical study shows that Li2Ti6O13 inserts ca. 5 Li per formula unit in the voltage range 1.5–1.0 V vs. Li+/Li, yielding a specific discharge capacity of 250 mAh g−1 under equilibrium conditions. Insertion occurs at an average equilibrium voltage of 1.5 V which is observed for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. However, a capacity loss of ca. 30% is observed due to a phase transformation occurring during the first discharge. After the first redox cycle a high reversible capacity is obtained (ca. 160 mAh g−1 at C/12) and retained upon cycling. Taking into consideration these results, we propose Li2Ti6O13 as an interesting material to be further investigated as the anode of lithium ion batteries.