Novel Sol-Gel Synthesis of LiMn2O4 and LiNixCo1-xO2 Powders

Abstract

A modified complex sol-gel process was developed to synthesize LiMn2O4 and LiNixCo1-xO2 powders. Sols were prepared from 1.5 M of Mn2+ or 1 M of xNi2+ and (1-x)Co2+ acetates plus ascorbic acid aqueous solutions by alkalizing them with LiOH and NH4OH. Ascorbic acid was added to prevent precipitation in the precursor solutions. When the sols were concentrated to one-third of their initial volume under reduced pressure and then gelled by drying for 10 days, heat treatment to ≥700 °C was accompanied by foaming, violent self-ignition, and formation of carbonates in the Ni-containing species. Significant improvements to the process and resulting powders were gained by modifying the gelation step. When gelation and drying were carried out under reduced total pressure, subsequent heating produced self-ignition, but no foaming, for all heating rates. The resulting products were determined to be nearly phase pure and carbonate free by thermogravimetric, differential thermal, X-ray, and infrared spectroscopy methods.