Mg-substituted LiNi0.5-xMgxMn1.5O4 (x = 0, 0.02, 0.05, and 0.10) are prepared via a spray pyrolysis method followed by a two-step heating at 600 degrees C for 6 h and 800 degrees C for 8 h in air. The compositions, morphology, and crystalline structure are studied with ICP-OES, SEM, XRD, and NPD, respectively. The XRD and NPD results are refined with Rietveld method to reveal the crystallography and phase composition of the prepared samples. The electrochemical properties of the obtained samples are investigated with results of capacity retention and cyclic voltammetric studies. Samples synthesized in this study manifest promising rate capability that may be due to the presence of major Fd (3) over barm phase with a minor amount of P4(3)32. Among the prepared samples, LiNi0.4Mg0.1Mn1.5O4 demonstrates the lowest capacity fading rate among the prepared samples at 0.1 similar to 5C rates when cycled between 3.5 and 5.1 V at temperatures of 30 and 60 degrees C. 2013 Elsevier B.V. All rights reserved.