Ethanothermal Synthesis of Octahedral-Shaped Doped Mn2O3 Single Crystals as a Precursor for LiMn2O4 Spinel Cathodes in Lithium-Ion Batteries

Abstract

Micrometer-sized particles of single-crystalline octahedral-shaped Mn2O3 doped with various elements (Al, Ti, Ni, and Zr) have been obtained by an ethanothermal synthesis at 150 °C. The doping of other element(s) into the Mn2O3 framework is characterized by energy-dispersive X-ray spectroscopy and X-ray powder diffraction. With Ni as a dopant, however, the particle morphology changed dramatically to spheres. The doped Mn2O3 with octahedral morphologies was employed as a precursor for the preparation of doped spinel LiMn2O4 cathodes for lithium-ion batteries. The doped samples exhibit enhanced cycle life, with the Al and Ti codoped sample displaying ∼90% capacity retention after 100 cycles at C/3 rate in full cells with a graphite anode. In addition, replacing 25 vol % of ethanol with water as the solvent for the solvothermal synthesis gives a rod-shaped γ-MnOOH structure instead of α-Mn2O3, which will be attractive for future studies of unique physicochemical properties originating from the shape.