Materials Research Bulletin, Vol.44, No.3, 707-713, 2009
Synthesis of spherical nanostructured LiMxMn2-xO4 (M = Ni2+, Co3+, and Ti4+; 0 <= x <= 0.2) via a single-step ultrasonic spray pyrolysis method and their high rate charge-discharge performances
LiMxMn2-xO4 (M = Ni2+, Co3+, and Ti4+; 0 <= x <= 0.2) spinels were prepared via a single-step ultrasonic spray pyrolysis method. Comparative studies on powder properties and high rate charge-discharge electrochemical performances (from 1 to 15 C) were performed. XRD identified that pure spinel phase was obtained and M was successfully substituted for Mn in spinel lattice. SEM and TEM studies confirmed that powders had a feature of 'spherical nanostructural', that is, powders consisted of spherical secondary particles with the size of about 1 mu m, which were developed from close-packed primary particles with several tens of nanometers. Substitutions enhanced density of second particles to different extents, depending on M and its content. Charge-discharge tests showed that as-prepared LiMn2O4 could deliver excellent rate performance (around 100 mAh/g at 10 C). Ni substitution contributed to improving electrochemical performances. In the voltage range of 4.95-3.5 V, the materials showed much better electrochemical performances than LiMn2O4 in terms of capacity, cycleability and rate capability. (C) 2008 Elsevier Ltd. All rights reserved.
Keywords:Inorganic compounds;Nanostructures;X-ray diffraction;Electrochemical measurements;Electrochemical properties