LiNi[sub 0.5]Mn[sub 1.5]O[sub 4] Showing Reversible Phase Transition on 3 V Region

Abstract

Spinel LiNi 0 . 5 Mn 1 . 5 O 4 powders with different space group of Fd3m and P4 3 32 were synthesized by an ultrasonic spray pyrolysis method. The morphologies of the prepared powders depended on their structures; polyhedral shape for Fd3m and octahedral for P4 3 32. The obtained discharge capacities of the Fd3m and P4 3 32 were about 60 mAh g - 1 and 70 mAh g - 1 , respectively. Structural changes of both compounds were investigated on 3 V region by ex situ X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). From the ex situ XRD and HRTEM studies, LiNi 0 . 5 Mn 1 . 5 O 4 having P4 3 32 symmetry showed that structural transition occurred reversibly from simple cubic (P4 3 32) to tetragonal phase (I4 1 /amd), whereas irreversible structural changes were observed for Fd3m symmetry on 3V region.