The effect of cationic disordering on the electrochemical performances of the layered nitrides LiWN2 and Li0.84W1.16N2

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.