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The effect of mechanical grinding on the electrochemical properties of Li2Ti3O7 regarding lithium insertion is studied. X-ray diffraction experiments of milling compounds showed a progressively amorphization of the crystalline material due to both crystalline size decreasing and internal strain increasing. These structural modifications are reflected in the electrochemical behavior of Li2Ti3O7, when it is used as the positive electrode in lithium cells. As a function of milling time a higher specific capacity is obtained during the first discharge of the cell, but when charging an increasing in the irreversible capacity is observed. The most promising Li2Ti3O7 based electrode has been achieved, under our experimental conditions, for 13 hours milling that produces a compound with crystallite size of approximately 20 nm. [ABSTRACT FROM AUTHOR]

Abstract: The layered nitrides LiWN2 and Li0.84W1.16N2 are investigated related to their electrochemical performances as possible electrodes for rechargeable lithium batteries. In the case of LiWN2, for which Li and W atoms are ideally ordered in alternating Li and W layers, de-intercalation of lithium proceeds up to 50%. The de-intercalated lithium can be intercalated again subsequently. The reversible reaction is the origin of the high cyclability observed in the corresponding lithium cells. On the other hand, in Li0.84W1.16N2 the Li layers are statistically occupied by tungsten (16%) and lithium (84%). A clear effect of the disordered cationic occupation on the electrochemical behaviour has been found, since for Li0.84W1.16N2 a very low extraction rate is obtained during the first oxidation (0.03 Li per formula unit). In addition, cyclability is rather poor. The very different electrochemical behaviour is explained by the structural differences between both layered nitrides. [Copyright &y& Elsevier]