Investigating the Structural and Lithium Storage Properties of High-Entropy Oxides in the Mg-Co-Ni-Cu-Zn-O System

Abstract

Recently, a new class of materials known as high-entropy oxides (HEOs) has emerged as an alternative electrode material for the next-generation Li-ion batteries. However, the discovery of these materials brings forth a broad range of compositions remained unexplored. This study aimed to investigate the structural and electrochemical characteristics of the non-equiatomic HEOs. Accordingly, ten different samples were synthesized in the Mg-Co-Ni-Cu-Zn-O system at very high (35 mol. %) and very low (5 mol. %) constituent proportions. Our experimental and theoretical results indicated that the thermodynamic stability of the HEOs was affected significantly by the enthalpic contributions arising from the lattice strain. These findings may provide a more consistent design approach in selection of a suitable component for the synthesis of the single-phase HEOs. Furthermore, the specific capacity, cycling stability and lithiation voltage of the electrodes have also been shown to be influenced by each individual constituent of the electrode.