Electrochemical performance of spinel LiMn2O4 cathode materials made by flame-assisted spray technology

Spinel lithium manganese oxide LiMn2O4 powders were synthesized by a flame-assisted spray technology (FAST) with a precursor solution consisting of stoichiometric amounts of LiNO3 and Mn(NO3)2·4H2O dissolved in methanol. The as-synthesized LiMn2O4 particles were non-agglomerated, and nanocrystalline. A small amount of Mn3O4was detected in the as-synthesized powder due to the decomposition of spinel LiMn2O4 at the high flame temperature. The impurity phase was removed with a post-annealing heat-treatment wherein the grain size of the annealed powder was 33 nm. The charge/discharge curves of both powders matched the characteristic plateaus of spinel LiMn2O4 at 3 V and 4 V vs. Li. However, the annealed powder showed a higher initial discharge capacity of 115 mAh g−1 at 4 V. The test cell with annealed powder showed good rate capability between a voltage of 3.0 and 4.3 V and a first cycle coulombic efficiency of 96%. The low coulombic efficiency from capacity fading may be due to oxygen defects in the annealed powder. The results suggest that FAST holds potential for rapid production of uniform cathode materials with low-cost nitrate precursors and minimal energy input.