Ce and Cu co-doped LiMn2O4 cathode material: Synthesis, characterization and electrochemical performances

Abstract

In this study, a rare earth (Ce) and a conventional transition metal (Cu) are doped to investigate the improvement in the electrochemical nature of LiMn2O4 (LiMn2-x-yCexCuyO4 (0.01 ≤ x ≤ 0.05 and y = x)) using the sol-gel method assisted by citric acid as the chelating element. The physiochemical properties of co-doped cathode material are evaluated and analyzed using XRD, TG/DTA, SEM, TEM with EDS, FT-IR and Raman spectra. By increasing the concentration of the dopants, the Mn oxidation states increased, which indicated the embedding of the dopants into the structure of the cathode compound and also restricted the Jahn-Teller effect. The cubic spinel structure with space group Fd3‾m was revealed by the structural investigation, and the average grain size ranged from 0.36 to 0.59 μm. The TEM patterns confirm that there is no aggregation in the compound's structure. The high conductivity and stability of Cu contribute effectively to its benefits in decreasing capacity fade. LiMn2-x-yCexCuyO4 was enriched with dual doping in order to enhance the stability of structure of the cathode material. Finally, the charge/discharge curves of the electrochemical cells of LiMn1.94Ce0.03Cu0.03O4 were performed and the discharge and retension capacity of the synthesized LiMn1.94Ce0.03Cu0.03O4 samples are 89.70 mAh.g−1 (1st cycle), 77.4 mAh.g−1 (2nd cycle) and 86.28 %, which are better than the LMO.