Preparation of Li(Ni 0.5Mn 1.5)O 4 by polymer precursor method and its electrochemical properties

Abstract

We have prepared a 4.8 V voltage cathode, Li(Ni 0.5Mn 1.5)O 4 using the polymer polyvinylpyrrolidone (PVP) as precursor at temperatures ranging from 700 to 750 °C for 6 h in air. The Rietveld refined X-ray diffraction patterns of Li(Ni 0.5Mn 1.5)O 4 showed a spinel type structure with a lattice parameter value of ∼8.174(2) . The Scanning Electron Microscope (SEM) images showed particle size in the range, ∼100-3000 nm. The surface area of the prepared powders was characterized by the Brunauer-Emmett-Teller (BET) technique. Cathodic electrochemical properties were evaluated using cyclic voltammetry (CV) and galvanostatic cycling (GC) in the range 3.5-5.0 V vs. Li/Li + at ambient temperature. CV studies showed a minor peak at ∼4.0 V due to the Mn 3+/4+ redox couple, and main anodic/cathodic peaks at 4.75/4.6 V and 4.8/4.7 V corresponding to the Ni 2+/4+ redox couples. The GC studies were carried out at the current rates (C/4.5) 30 mA g -1 and (C/1.2) 120 mA g -1, at room temperature. The reversible capacities of all samples prepared at 700-750 °C are in the range, 92-130 (±3) mAh g -1 at the end of 15th cycle. Impedance studies were carried out on a selected cell. © 2012 Elsevier Ltd.