Neutron diffraction and Raman analysis of LiMn1.5Ni0.5O4 spinel type oxides for use as lithium ion battery cathode and their capacity enhancements

LiMn1.5Ni0.5O4 cathode materials for lithium ion batteries (LIBs) were synthesized by the low cost wet-chemical Pechini technique. Phase analysis by X-ray diffraction shows that extended heat treatment at 900 degrees C causes precipitation of LixNi1 - xO with consequent reduction in specific energy capacity. Raman spectroscopy and powder neutron diffraction have been extensively integrated into characterization of variously annealed samples and provided key information on Ni-Mn order-disorder for samples studied electrochemically. A fully disordered, nano-crystalline product (space group Fd-3m) is obtained at 600 degrees C, while ordered materials (space group P4(3)32) are obtained for samples with a final treatment at 700 degrees C. Crystallographic data are obtained from Rietveld refinements. Samples treated at 600 and 700 degrees C are received as nano-sized particles, similar to 10 and similar to 50 nm, respectively, while well faceted particles are obtained at higher temperatures. The addition of propylene carbonate significantly improves cathode performance when followed by a leaching step that yields a porous cathode tape. The ordered material calcinated at 900 degrees C and thereafter at 700 degrees C for 10 h shows a specific capacity of similar to 137 mAh/g at 0.04 C and similar to 130 mAh/g at 2 C discharge rates; the highest capacities so far reported for sub micron particles of the ordered phase. This study provides a route to performance enhanced pure LiMn1.5Ni0.5O4 spinel materials for LIB cathodes. (C) 2015 Elsevier B.V. All rights reserved.