Electrochemical and Microstructural properties of High-Entropy spinel oxides (Mg 0.2 X 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 (X = Ti, Cr) as Lithium-Ion battery anodes

In recent years, high-entropy oxides (HEOs), especially those with spinel structures, have emerged as a new class of materials for lithium-ion battery anodes. Due to the unpredictable nature of these materials, it is crucial to synthesize and investigate various compounds. The effects of different elements in HEOs and their single-phase and multi-phase structures on the properties of HEOs are not yet fully understood. In this study, two HEOs with equimolar compositions (Mg 0.2 Ti 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 and (Mg 0.2 Cr 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 were prepared using a simple solid-state method. The effects of Ti and Cr elements on the material characteristics and their electrochemical performances were investigated. It was found that the properties of the materials change with variations in their elemental composition. X-ray diffraction (XRD) results show that the compound (Mg 0.2 Ti 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 has a single-phase spinel structure, while (Mg 0.2 Cr 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 contains two phases: spinel and rock-salt. Morphological analysis of the two samples reveals that the grain shapes are more uniform in the (Mg 0.2 Ti 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 sample. The superior electrochemical performance of (Mg 0.2 Ti 0.2 Zn 0.2 Ni 0.2 Fe 0.2 ) 3 O 4 as an anode material, achieving a reversible specific capacity of 327mAh g- 1 at 1000 mA/g, can be attributed to its single-phase structure, uniform morphology, and the stabilizing effect of Ti during cycling.