Structural reinforcement and electrochemical modulation of spinel LiMn₂O₄ through SmNi co-doping

Spinel-type Li (SmNi) x Mn 2- x O 4 cathode materials ( x = 0.01 to 0.05) were created using a sol-gel method. to investigate the effects of samarium (Sm) and nickel (Ni) co-doping on electrochemical characteristics and structural stability. Analysis of X-ray diffraction showed that at the lower doping concentration (x = 0.01), Sm and Ni co-doping effectively inhibited The Jahn-Teller distortion linked to (Manganese) Mn 3+ ions, enhanced the crystallinity of the structure of spinel, and facilitated lithium-ion diffusion. Raman spectroscopy and Fourier-transform infrared spectroscopy confirmed Mn O bond shortening and lattice distortion with increasing dopant content. Transmission electron microscopy showed particle sizes in the range of 100–150 nm, Energy dispersive X-ray spectroscopy, however, verified the elemental makeup of the synthesized material. Electrochemical impedance spectroscopy demonstrated a low charge-transfer resistance (R_ct = 98 Ω) for the x = 0.01 sample. Cyclic voltammetry (CV) measurements demonstrated that co-doping at optimal concentrations resulted in a small peak potential separation (ΔEp) for the x = 0.01 sample, indicating improved redox reversibility and the Galvanostatic Charge-Discharge studies showed Specific Capacity 118 mAh/g in the beginning of cycling decreased to 108 mAh/g representing 92% capacity retention after 100 cycles. These results suggest that dual doping with Sm and Ni is an effective strategy to improve LiMn 2 O 4 -based cathode materials' long-term performance in lithium-ion batteries.