Lithium insertion in lithium iron molybdate

We report here, for the first time, facile and reversible insertion/extraction of lithium in LiFe(MoO 4) 2. A biphasic reaction is observed in the compositional range 0 < x < 0.9 in Li 1 + xFe(MoO 4) 2 with a remarkably flat plateau at an average voltage of 2.68 V due to the redox couple Fe 3 +/Fe 2 +. An irreversible structural change was associated with lithium insertion. The plateau behavior is reversible with negligible hysteresis (ΔdQ/dV = 0.05 V) and 100% Faradaic efficiency. A reversible capacity of 63 mAh/g is obtained in the voltage window 3.0-2.5 V. When reduction of Mo 6 + is also accessed by cycling in the voltage window 3.0-1.0 V, a reversible capacity of ~ 180 mAh/g was obtained at the end of 20 cycles at C/5 rate. © 2012 Elsevier B.V.