Effect of the Crystal Chemistry of LiNi1/2Mn3/2O4 Spinels on its Electrochemical Properties

LiNi1/2Mn3/2O4 with the spinel structure is a promising candidate as a h igh power electrode material due to its open 3D structure for Li-ion diffusion and high operating voltage by redox of Ni+2/+4 (~4.7 V vs. Li/Li+) [1]. This compound is well known to crystallize in two polymorphs depending on the ordering of Ni and Mn in the octahedral sites, Fd 3 m (d isordered) and P433 2 (ordered) [2,3]. Such ordering is controlled by temperature of synthesis, with a t ransition occurring at ~700°C [4,5]. Although many earlier studies reported that ordering affects the electrochemical propert ies, they have not been fully successful in separating this effect from other parameters such as microstructure or composition, e.g., presence of Mn3+ defects in the structure [6]. By a controlled procedure of post-synthesi