A Li-rich spinel was prepared by sintering a mixture of LiOH and MnO2 at 1000 degrees C and then annealing at lower temperature together with extra LiOH. The new material with formula Li1.094Mn1.906O4.025 based on chemical analysis belongs to a new kind of oxygen stoichiometric spinels with metal vacancies on 16d sites as expressed by [Li](8a)[Li(0.087)Mn(1.894)square(0.019)] (16d)[O-4](32e) in terms of site assignments (square represents vacancies). With Li-doping and the presence of vacancies on 16d sites, the structural stability was enhanced and capacity retention at elevated temperature was improved significantly. In addition, the new material shows very low Mn dissolution that is necessary for stable cycling performance of Li-ion batteries based on spinel cathodes. (C) 2005 The Electrochemical Society.