Influence of the lattice parameter difference between the two cubic phases formed in the 4 V region on the capacity fading of spinel manganese oxides

To develop a better understanding of the capacity-fading mechanisms of spinel lithium manganese oxides, the electrochemical properties, degree of manganese dissolution, and crystal chemistry of a number of singly substituted LiMn2-yMyO4 (M = Li, Al, Ti, Co, and Ni and 0 less than or equal to y less than or equal to 0.2) and doubly substituted LiMn2-y-zMyLi0.075O4 (M = Ti, Co, and Ni, 0 less than or equal to y less than or equal to 0.1, and 0 less than or equal to z less than or equal to 0.1) oxides have been compared with those of LiMn2O4. The cation-substituted spinel manganese oxides show better electrochemical performances than LiMn2O4. Especially, the doubly substituted LiMn1.85Ni0.075Li0.075O4 exhibits excellent cyclability at both ambient and elevated temperatures with a capacity of around 100 mAh/g. It also exhibits remarkable rate capability and excellent capacity retention (>95%) after storage at 60 degreesC at various depths of discharge (DOD). Although the degree of manganese dissolution does not vary significantly, the spinel manganese oxides show a clear relationship between the percent capacity fade and the lattice parameter difference (Deltaa) between the two cubic phases formed in the 4 V region. A smaller Deltaa and the associated negligible volume change (DeltaV) appear to minimize the microstrain, maintain good interparticle contact, and lead to superior electrochemical performances. The excellent cyclability and high rate capability of the LiMn2-y-zNiyLizO4 oxides may make them attractive for electric vehicles.