Effects of multi-dopants (Zn and Ho) in stabilizing spinel structure for cathode materials in lithium rechargeable batteries—Novel chelated sol–gel synthesis

• Multi-doped pristine spinels used as cathode materials were synthesized via sol–gel method.
• The synthesized samples exhibited high degrees of crystallinity and good phase purity.
• LiZn0.10Ho0.10Mn1.80O4 was an appropriate candidate for use in lithium-ion rechargeable batteries.

Multi-doped spinels, namely LiMn2O4 and LiZnxHoyMn2−x−yO4 (x = 0.10–0.18; y = 0.02–0.10), for use as cathode materials for lithium-ion rechargeable batteries were synthesized via sol–gel method, using lauric acid as the chelating agent, to obtain micron-sized particles. The physical properties of the synthesized samples were investigated using differential thermal analysis, Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, energy-dispersive X-ray analysis, and electrochemical methods. XRD showed that LiMn2O4 and LiZnxHoyMn2−x−yO4 have high degrees of crystallinity and good phase purities. The SEM images of LiMn2O4 showed an ice-cube morphology with particles of size 1 μm. Charge–discharge studies showed that undoped LiMn2O4 delivered the discharge capacity of 124 mA h/g with coulombic efficiency of 95% during the first cycle, whereas doped spinels delivered discharge capacities of 125, 120, and 127 mA h/g in the first cycle with coulombic efficiencies of 96%, 91%, and 91%, respectively.

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