Structure and stability of Li-Mn-Ni composite oxides as lithium ion sieve precursors in acidic medium

A series of spinel Li-Mn-Ni composite oxides with theoretical chemical formula of LiNixMn2-xO4 (0 <= x <= 1.0) were synthesized by liquid phase method. Their structure and morphology were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. The stability of these Ni-substituted spinel oxides prepared at different temperatures was investigated in acidic medium as well. The results show that Ni can be brought into the spinel framework completely to form well-crystallized product when x <= 0.5 and the optimized synthesis temperature is 800 degrees C. LiNi0.4Mn1.6O4 prepared at 800 degrees C can maintain the spinet structure and morphology with Li extraction ratio of 30.37%, Mn extraction ratio of 8.78% and Ni extraction ratio of 1.82% during acid treatment. The incorporated Ni not only inhibits the dissolution of Mn, but also reduces the extraction of Li due to the lattice contraction.