A new approach to improve the electrochemical performance of ZnMn2O4 through a charge compensation mechanism using the substitution of Al3+ for Zn2+

Abstract

ZnMn2O4 and Zn1-xAlxMn2O4 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 Al3+ for Zn2+ 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 Zn1-xAlxMn2O4, 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.