The simultaneous partial replacement of Ni and Mn by Fe and Ti in the 5-V LiNi0.5Mn1.5O4 spinel was studied. The spinel structure is preserved after double substitution of iron and titanium, while partial tetrahedral site occupancy by iron ions was observed. The best capacity retention in lithium cells was achieved by double substitution for the LiFe0.10Ti0.10Ni0.45Mn1.35O4 composition, associated with the particular single-phase mechanism of lithium extraction combined with the structural stabilization induced by titanium and tetrahedral iron. In addition, the capacity is higher for smaller particle sizes, while a slightly higher capacity retention is found for larger, regularly shaped particles. (c) 2005 The Electrochemical Society.