Abstract

Lithium manganese oxides are of great interest as cathode materials for lithium-ion batteries. We describe here a new combustion method to synthesize lithium manganese oxides directly from lithium nitrate, manganese nitrate, ammonium nitrate and glycol. The resultant LiMn₂O₄ synthesized under the optimum synthesis conditions shows perfect spinel structure and uniform particle size distribution. The combustion products were characterized by scanning electron microscopy. And, powders X-ray diffraction and transmission electron microscopy were used to characterize the products. Lithium manganese oxides with approximately acerose crystal morphology of 100 - 200 nm length with 10 - 15 nm diameters and a variety of morphologies were found. The oxides produced by this cheap method affirmed the validity of combustion synthesis of fine powders. Lithium manganate with a fine structure different from that of the normal spinel is formed after combustion wave treatment due to the addition of ammonium nitrate. It might also provide a cheap large-scale synthesis method. Reagents combustion with the addition of ammonium nitrate is strongly nonequilibrium processes. Free metal atoms are first released with the decomposition of reagents, and then theses metal and oxygen atoms are rearranged, coagulated and finally crystallized into lithium manganate during the expansion of combustion process.

Key words: Spinel phase LiMn2O4, combustion method, ammonium nitrate, acerose crystal.