Lithium-deficient Li Y Mn2O4 spinels (LD-Li Y Mn2O4) with nominal composition (0.9≤ Y <1) have been synthesized by melt impregnation from Mn2O3 and LiNO3 at temperatures ranging from 700°C to 850°C. X-ray diffraction data show that LD-Li Y Mn2O4 spinels are obtained as single phases in the range Y =0.975–1 at 700°C and 750°C. Morphological characterization by transmission electron microscopy shows that the particle size of LD-Li Y Mn2O4 spinels increases on decreasing the Li-content. The influence of the Li-content and the synthesis temperature on the thermal and electrochemical behaviours has been systematically studied. Thermal analysis studies indicate that the temperature of the first thermal effect in the differential thermal analysis (DTA)/thermogravimetric (TG) curves, T C1, linearly increases on decreasing the Li-content. The electrochemical properties of LD-Li Y Mn2O4 spinels, determined by galvanostatic cycling, notably change with the synthesis conditions. So, the first discharge capacity, Q disch., at C rate increases on rising the Li-content and the synthesis temperature. The sample Li0.975Mn2O4 synthesized at 700°C has a Q disch. =123mAhg−1 and a capacity retention of 99.77% per cycle. This LD-Li Y Mn2O4 sample had the best electrochemical characteristics of the series.