A new route for the synthesis of LiMn2O4 cathode: Variation of composition, microstructure, and electrochemical behavior with synthesis temperature

LixMn3-xO4 (x similar to 1.08) spinel oxides have been synthesized by a new procedure. The method involves an ambient temperature synthesis of MnO2 by reducing aqueous KMnO4 with KBH4 followed by an ambient temperature insertion of Li into MnO2 and firing at various temperatures ranging from 550-900 degrees C. The oxygen content and the oxidation state of manganese decrease with increasing synthesis temperature, which results in an increase of the unit cell parameter a with synthesis temperature. The particle size increases from about 300 nm to about 1.3 mu m as the synthesis temperature increases from 550 degrees C to 900 degrees C. Preliminary electrochemical data reveal that the sample synthesized at 700 degrees C exhibits better capacity and cyclability compared to the samples obtained at 550 and 850 degrees C.