Search

Abstract: 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 1.5–1.0V vs. Li+/Li, yielding a specific discharge capacity of 250mAhg−1 under equilibrium conditions. Insertion occurs at an average equilibrium voltage of 1.5V 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. 160mAhg−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. [ABSTRACT FROM AUTHOR]

The effect of mechanical grinding (MG) on the electrochemical properties of Si3N4 is studied as the processing produces different particle size. The evolution of the amorphisation stage has been monitored by X-ray diffraction (XRD), although particle size has also been studied through transmission electron microscopy experiments. Processed Si3N4 has been used as the positive electrode in electrochemical cells, where the negative electrode is lithium. We do not expect an intercalation process during the discharge step of such a type of cell, but a behaviour similar to that named as “convertible compounds”. As the main result, the specific capacity of these lithium cells is increased up to 34% in relation to the starting, non-milled material. However, even though the size of the Si3N4 particles has been reduced, from micrometer to nanometer scale, no appreciable changes in the cycling behaviour is observed when compared with the pristine material. [Copyright &y& Elsevier]