Influence of Al Substitution on the Electrochemical Performance of Spinel LiMi0.5-xMn1.5AlxO4 Cathode

Al-doped LiNi0.5-xMn1.5AlxO4 cathodes materials were synthesized by a simple sol-gel method. The structure and electrochemical properties have been investigated systematically by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectra, cyclic voltamogram (CV), charge-discharge tests and Ac impedance spectroscopy. XRD patterns reveal that trace of LixNi1-xO-like impurity phase exists in the pristine LiNi0.5Mn1.5O4 and is suppressed by substituting of Ni2+ with Al3+. With Al3+-substitution, the electrochemical performance of spinel cathodes are enhanced, which is ascribed to the improvement of structural stability and electronic conductivity as well as the suppression of impurity phase. However, the discharge capacity deteriorates in the case of LiNi0.40 Mn1.5Al0.10O4 spinel, which might result from the blocking of migration pathway of electrons in octahedral site.