Characterization of Zn- and Fe-substituted LiMnO2 as cathode materials in Li-ion cells

Layered LiMn1-xMxO2 (M=Zn or Fe) (0 <= x <= 0.3) samples are synthesized from the corresponding sodium analogues by an ion-exchange method using LiBr in n-hexanol at 160 degrees C. The samples are subjected to physicochemical an d electrochemical characterization. X-ray diffraction data indicate the formation of layered structures for the LiMn1-xZnxO2 samples up to x = 0.3 and for LiMn1-xFexO2, samples up to x = 0.2. Among these, LiMn0.95Zn0.05O2 and LiMn0.95Fe0.05O2 provide the highest capacity values of 180 and 193 mAh g(-1), respectively. Both Zn- and Fe-substituted samples display good capacity retention up to 30 charge-discharge cycles. Electrochemical impedance spectroscopy and galvanostatic intermittent titration data corroborate the results obtained from cyclic volatmmetry and charge-discharge cycling. (c) 2006 Elsevier B.V. All fights reserved.