Nanostructured Electroceramics

In modern electrochemical applications, nanoparticles are of growing interest as small dimensions reduce diffusion lengths within particles and increase the number of active sites for surface reactions decreasing the local current density. Thus, when nanoparticles are used as electroactive materials in secondary (rechargeable) lithium-ion batteries, the resulting overpotentials are expected to be lower and the charging/discharging rates should be higher. The control of crystallinity, particle size, and morphology as well as both productivity and cost efficiency are important for their applications.

Electroactive LiMn2O4, Li4Ti5O12, and LiFe3O4 particles with spinel structure (normal, mixed, and mixed inverse) were made by flame spray pyrolysis (FSP), a fast and versatile process for the synthesis of functional nanoparticles, at production rates of 10 to 20 g h-1. These materials of high specific surface area had a primary crystallite size in the range of 8 to 30 nm and exhibited high temperature stability.

Electrochemical properties, as measured by slow cyclic voltammetry, are reported for LiMn2O4 and Li4Ti5O12 as potential cathode and anode materials, respectively, in secondary lithium-ion batteries. LiFe5O8 nanoparticles were made also by FSP containing the electrochemically active beta-phase as shown by the corresponding cyclic voltammogram and specific charge-discharge spectra.