Improvement of the cycling performance of LiMn[2]O[4] as cathode material for lithium batteries by Cr, Al, Co and Ni substitution

ABSTRACT

The main advantages of LiMn[2]O[4] spinel system are low cost, high cathode potential versus lithium and lack of toxic metals such as cobalt or nickel present in LiCoO[2] and LiNiO[2] cathode materials whereas the main drawback of the system is the fading capacity during cycling as compared to LiCoO[2] and LiNiO[2]. To improve the structural and electrochemical properties of LiMn[2]O[4], as cathode material for lithium secondary batteries, Co, Cr, AI and Ni ions were substituted for manganese ions. LiMn[2]O[4], and LiM[gamma]Mn[2-gamma]O[4] [M = Al, Co, Cr and Ni; gamma = 1/6] samples were prepared by solid state reactions. The X-ray powder diffraction patterns of the substituted samples are almost identical to the parent sample. A well defined highly pure spinel was characterized for all samples without observation of extra phases for substituted samples. The electrochemical performance of the prepared samples was evaluated through cyclic voltammetry and galvanostatic charge/discharge operations. The first discharge capacities of the substituted spinels are lower than that of LiMn[2]O[4], but better cycling performance and capacity retention was observed for the substituted spinels compared to the parent LiMn[2]O[4],. The improvement in the cycling performance of LiM[gamma]Mn[2-gamma]O[4][M = Co, Cr, Ni and Al; gamma = 1/6] compared to that of parent LiMn[2]O[4] is attributed to the stabilization of the spinel structure by the substituted metal cations