Al-doped spinel LiAl0.1Mn1.9O4 with improved high-rate cyclability in aqueous electrolyte

To improve the cyclability of spinel LiMn2O4 in aqueous electrolyte, Al-doped LiAlxMn2−xO4 (x = 0.05, 0.1, 0.15) materials are prepared using a room-temperature solid-state grinding reaction followed by calcination at different temperatures for different durations, respectively. Their phase structures and morphologies are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Electrochemical performances of the materials are investigated by cyclic voltammetry and galvanostatic charge/discharge methods. XRD results reveal that the crystallinity of the LiAl0.1Mn1.9O4 increases with increasing calcination temperature and calcination time. However, when the calcination temperature is increased to 800 °C, a small amount of Mn3O4 impurity phase is detected in the product calcined for 12 h, due to the decomposition of LiAl0.1Mn1.9O4, while the product calcined for a shorter time of 3 or 6 h is found to be LiAl0.1Mn1.9O4 single phase. TEM results confirm that the grain size of the materials increases with increasing calcination temperature. Electrochemical experiments demonstrate that the charge/discharge cyclability of the LiAl0.1Mn1.9O4 increases with increase in calcination temperature and calcination time. Compared with the pristine LiMn2O4, the Al-doped LiAlxMn1−xO4 show the obviously improved cyclability, especially for the LiAl0.1Mn1.9O4 calcined at an elevated temperature for 12 h.