La and Ni Co-doping Effect in LiMn₂O₄ on Structural and Electrochemical Properties for Lithium-Ion Batteries

Reliable, low-cost electrocatalysts of La and Ni co-doped LiMn₂O₄ for energy storage applications were successfully synthesized via the sol-gel method. Herein, the effect of La³⁺ and Ni²⁺ co-doping in Mn³⁺ of LiMn_2−x(LaNi)_xO₄ (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) samples were studied. X-ray diffraction (XRD) results for structural characterization established the cubic spinel structure of the materials. Microstructural studies of the synthesized materials via field emission scanning electron microscopy (FE-SEM) revealed that the particle size was reduced with La³⁺and Ni²⁺ doping. The electrochemical properties that were investigated in the voltage range of 0.2–1.2 V showed improved structural stability, and therefore Jahn–Teller distortion was effectively suppressed. Cyclic voltammetry (CV) revealed that a 4% substitution of (La and Ni) in Mn³⁺ exhibited improved lithium-ion reversibility. Electrochemical impedance spectroscopy (EIS) showed an improved charge transfer resistance of 41 Ω for (LaNi) 0.04 doping over other doping concentrations and pure LiMn₂O₄. Charge-discharge studies revealed that the initial discharge capacity of LiMn_1.92(LaNi)_0.04O₄ is 132.1 mAh/g in aqueous Li₂SO₄ electrolyte is improved over other doping concentrations and pristine LiMn₂O₄.