Phthalic acid assisted nano-sized spinel LiMn2O4 and LiCrxMn2−xO4 (x = 0.00–0.40) via sol–gel synthesis and its electrochemical behaviour for use in Li-ion-batteries

Nano-sized particles of spinel LiMn2O4 and LiCrxMn2−xO4 (x = Cr; 0.00–0.40) have been synthesized using phthalic acid as chelating agent for the first time by sol–gel method. When compared to solid-state synthesis method, the sol–gel route reduces heating time of synthesize and to obtain particles of uniform surface morphology. The synthesized samples were characterized through thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM images of the parent compounds show nanospherical grains of LiMn2O4 when compared to chromium-doped ones. XRD patterns of LiMn2O4 ascertain amorphous nature and for high calcined LiCrxMn2−xO4 single phase highly crystalline patterns were obtained. TEM images of the parent and chromium-doped spinel particles depict individual grain morphology with well-separated grain boundaries. LiCr0.10Mn1.90O4 excels in discharge and cycling behaviour and offer higher columbic efficiency, when compared to un-doped LiMn2O4. Cyclic voltammograms of LiMn2O4 and LiCrxMn2−xO4 exhibit oxidation and reduction peaks corresponding to Mn3+/Mn4+ and Cr3+/Cr4+.