Factors influencing the capacity fade of spinel lithium manganese oxides

With the aim of developing a better understanding of the capacity fading mechanisms of spinel manganese oxides, the percent capacity fade of a number of singly substituted LiMn2-yMyO4 (M = Li, Al, Ti, Co, Ni, and Cu and 0 < or = y < or = 0.2) and doubly substituted LiMn2-y-zMyLizO4 (M = Al, Ti, Fe, Co, Ni, Cu, and Ga, 0 < or = y < or = 0.1, and 0 < or = z < or = 0.1) oxides is correlated to the initial lattice parameter, initial manganese valence, degree of manganese dissolution, electrode resistance, irreversible capacity (IRC) loss in the first cycle, and lattice parameter difference Deltaa between the two cubic phases formed in the two-phase region during the charge-discharge process. The doubly substituted LiMn2-y-zNiyLizO4 samples exhibit a combination of superior capacity retention and rate capability with lower IRC compared to LiMn2O4 despite a similar amount of manganese dissolution due to a low Deltaa and the consequent low microstrain. The samples with a low Deltaa are also characterized by a lower initial lattice parameter and a higher initial Mn valence of > 3.58+ for the as-prepared samples. The percent capacity fade, IRC, and Aa all exhibit a sharp decrease as the initial Mn valence in the as-prepared sample exceeds 3.58+.