Search

We report the synthesis and nanostructuraldevelopment of polycrystallineand single crystalline LiFePO4(LFP) nanostructures usinga solvothermal media (i.e., water–tri(ethylene glycol) mixture).Crystal phase and growth behavior were monitored by powder and synchrotronX-ray diffraction, as well as transmission electron microscopy (TEM),while particle morphologies were examined using scanning electronmicroscopy (SEM). Initially, thin (100 nm) platelets of Fe3(PO4)2·8H2O (vivianite, VTE)formed at short reaction times followed by the nucleation of LFP (20nm particles) on the metastable VTE surfaces. Upon decrease in pH,primary LFP nanocrystals subsequently aggregated into polycrystallinediamond-like particles via an oriented attachment (OA). With increasingreaction time, the solution pH further decreased, leading to a dissolution–recrystallizationprocess (i.e., Ostwald ripening, OR) of the oriented polycrystallineLFP particles to yield evenly sized, single crystalline LiFePO4. Samples prepared at short reaction durations demonstrateda larger discharge capacity at higher rates compared with the singlecrystalline particles. This is due to the small size of the primarycrystallites within larger secondary LiFePO4particles,which reduced the lithium ion diffusion path while subsequently maintaininga high tap density. Understanding the relationship between solutionconditions and nanostructural development as well as performance revealedby this study will help to develop synthetic guidelines to enableefficient lithium ion battery performance. [ABSTRACT FROM AUTHOR]

Li[Ni1/3Co1/3Mn1/3]O2(L333) has been successfully synthesized through a two-stepcoprecipitationand annealing method. Crystal phase and growth behavior were monitoredby X-ray diffraction (XRD), while particle morphologies were observedby SEM and TEM. The crystal growth mechanisms during the annealingprocess were interpreted, and the growth exponent and activation energyfor crystal growth were calculated. At low temperatures (e.g., 600°C), L333 crystals are quite small (ca. 14 nm). Significant crystalgrowth occurs above 750 °C with crystallite diameters increasingto 850 ± 10 nm after 3 h at 1000 °C. [ABSTRACT FROM AUTHOR]