Modulating crystal structure and lithium-ion storage performance of high-entropy oxide (CrMnFeCoNiZn)3O4 by single element extraction

Abstract

High-entropy oxides (HEOs) have attracted attention as a promising anode material for lithium-ion batteries (LIBs), offering tunable element composition, desirable kinetic stability and entropy stabilization. Although the advantages of HEOs anodes with a high-entropy effect have been demonstrated, the impact of each element in certain HEOs is rarely discussed. In this work, a series of HEOs which is a pure spinel structure and a main spinel structure accompanied with an extra secondary rock-salt phase are obtained by single-element extraction based on the spinel-type HEO (CrMnFeCoNiZn)₃O₄. It is demonstrated that the element composition of HEOs plays a key role in the phase structure and electrochemical performance. For the structure, the high valence state cation (Cr, Mn, Fe) is essential for forming the purity spinel phase HEOs. For the electrochemical performance, a portion of Zn and Ni in the HEOs remains in the metal state after the first redox process, which plays a role in stabilizing the structural framework. The introduction of Fe is essential for capacity enhancement. Among the as-prepared HEOs, the (CrMnFeCoNiZn)₃O₄-(Cr) exhibits the most favorable lithium-ion storage performance, delivering an excellent specific capacity of 667.3 mAh g⁻¹ at 0.5 A g⁻¹ after 350 cycles. This work offers a useful strategy for designing elementary HEOs in the energy storage field.