Abstract
ZnMn(2)O(4) and Zn(1-x) Al (x) Mn(2)O(4) were synthesized by a spray drying process followed by an annealing treatment. Their structural and electrochemical characteristics were investigated by SEM, XRD, XPS, charge-discharge tests and EIS. XPS data indicate that the substitution of Al(3+) for Zn(2+) causes manganese to be in a mixed valence state by a charge compensation mechanism. Moreover, the presence of this charge compensation significantly improves the electrochemical performance of Zn(1-x) Al (x) Mn(2)O(4), such as increasing the initial coulombic efficiency, stabilizing the cycleability as well as improving the rate capability. The sample with 2% Al doping shows the best performance, with a first cycle coulombic efficiency of 69.6% and a reversible capacity of 597.7 mA h g(-1) after 100 cycles. Even at the high current density of 1600 mA g(-1), it still retained a capacity of 558 mA h g(-1).