Design and Performance of a New Zn_0.5Mg_0.5FeMnO₄ Porous Spinel as Anode Material for Li-Ion Batteries

Due to the low capacity, low working potential, and lithium coating at fast charging rates of graphite material as an anode for Li-ion batteries (LIBs), it is necessary to develop novel anode materials for LIBs with higher capacity, excellent electrochemical stability, and good safety. Among different transition-metal oxides, AB₂O₄ spinel oxides are promising anode materials for LIBs due to their high theoretical capacities, environmental friendliness, high abundance, and low cost. In this work, a novel, porous Zn_0.5Mg_0.5FeMnO₄ spinel oxide was successfully prepared via the sol-gel method and then studied as an anode material for Li-ion batteries (LIBs). Its crystal structure, morphology, and electrochemical properties were, respectively, analyzed through X-ray diffraction, high-resolution scanning electron microscopy, and cyclic voltammetry/galvanostatic discharge/charge measurements. From the X-ray diffraction, Zn_0.5Mg_0.5FeMnO₄ spinel oxide was found to crystallize in the cubic structure with Fd3¯m symmetry. However, the Zn_0.5Mg_0.5FeMnO₄ spinel oxide exhibited a porous morphology formed by interconnected 3D nanoparticles. The porous Zn_0.5Mg_0.5FeMnO₄ anode showed good cycling stability in its capacity during the initial 40 cycles with a retention capacity of 484.1 mAh g^-1 after 40 cycles at a current density of 150 mA g^-1, followed by a gradual decrease in the range of 40-80 cycles, which led to reaching a specific capacity close to 300.0 mAh g^-1 after 80 cycles. The electrochemical reactions of the lithiation/delithiation processes and the lithium-ion storage mechanism are discussed and extracted from the cyclic voltammetry curves.