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 °C. The samples are subjected to physicochemical and 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.