Structure and electrochemical performances of co-substituted LiSm x La0.2-x Mn1.80O4 cathode materials for rechargeable lithium-ion batteries

Spinel LiMn₂O₄ and Sm, La co-substituted LiSm _x La_0.2-x Mn_1.80O₄ (x?=?0.05, 0.10 and 0.15) cathode materials were synthesized by sol–gel method using aqueous solutions of metal nitrates and tartaric acid as chelating agent at 600 °C for 10 h. The structure and electrochemical properties of the synthesized materials were characterized by using thermogravimetric/differential thermal analysis, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, charge/discharge and electrochemical impedance spectroscopy studies. XRD analysis indicated that all the prepared samples were mainly belong to cubic crystal form with Fd3m space group. LiSm_0.10La_0.10Mn_1.80O₄ exhibits capacity retention of 90 % and 82 % after 100 cycles at room temperature (30 °C) and at elevated temperature (50 °C) at a rate of 0.5-C, respectively, much higher than those of the pristine LiMn₂O₄ (74 % and 60 %). Among all the compositions, LiSm_0.10La_0.10Mn_1.80O₄ cathode has improved the structural stability, high-capacity retention, better elevated temperature performance and excellent electrochemical performances of the rechargeable lithium-ion batteries.