Phthalic acid assisted nano-sized spinel LiMn2O4 and LiCr Mn2−O4 (x= 0.00–0.40) via sol–gel synthesis and its electrochemical behaviour for use in Li-ion-batteries

Abstract Nano-sized particles of spinel LiMn 2 O 4 and LiCr x Mn 2− x O 4 ( 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 LiMn 2 O 4 when compared to chromium-doped ones. XRD patterns of LiMn 2 O 4 ascertain amorphous nature and for high calcined LiCr x Mn 2− x O 4 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. LiCr 0.10 Mn 1.90 O 4 excels in discharge and cycling behaviour and offer higher columbic efficiency, when compared to un-doped LiMn 2 O 4 . Cyclic voltammograms of LiMn 2 O 4 and LiCr x Mn 2− x O 4 exhibit oxidation and reduction peaks corresponding to Mn 3+ /Mn 4+ and Cr 3+ /Cr 4+ .