Electrochemical Study of Li[sub 3]Fe(MoO[sub 4])[sub 3] as Positive Electrode in Lithium Cells

undergoes a complex electrochemical reaction with lithium in which the reduction of and takes place along the first discharge of the cell at about 2.4 and 1.8 V, respectively. The intercalation process involved is fully reversible for low lithium contents, with , the inserted compound retaining the parent framework with only a slight increase of the cell volume (0.85%). In contrast, the electrochemical reaction of with five lithium ions originates an irreversible decomposition of this material into a mixture of a FeO-type compound and an amorphous lithium-molybdate phase. This in situ formed blend is electrochemically active, being able to intercalate and deintercalate three lithium ions at an average voltage of 2 V (reversible specific capacity of ). The full discharge of the cells (down to the vicinity of 0 V) proceeds through the complete and irreversible reduction of with 25 lithium ions, resulting in the breakdown of any existing crystalline framework.