Structure and electrochemical properties of LiLa_xMn_2-xO₄ cathode material by the ultrasonic-assisted sol-gel method

Powders of spinel LiLa_xMn_2-xO₄ were successfully synthesized by the ultrasonic-assisted sol-gel (UASG) method. The structure and properties of LiLa_xMn_2-xO₄ were examined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electronic microscopy (SEM), galvanostatic charge-discharge test, and cyclic voltammetry (CV). XRD results show that the La³⁺ can partially reptace Mn³⁺ in the spinel and the doped materials with La³⁺ have a larger lattice constant compared with pristine LiMn₂O₄. FT-IR indicates that the absorption peak of Mn³⁺-O and Mn⁴⁺-O bonds has a red and blue shift with the increase of doping lanthanum in LiLa_xMn_2-xO₄, respectively. The charge-discharge test exhibits that the initial discharge capacity of LiLa_xMn_2-xO₄ drops off, and the capacity retention increases gradually at C/5 discharge rate with the increase of doping lanthanum, and LiLa_0.01Mn_1.99O₄ has a higher discharge capacity and a better cycling performance at 1C discharge rate. CV reveals that the doping La³⁺ is beneficial to the reversible extraction and intercalation of Li⁺ ions.