High entropy spinel-structure oxide for electrochemical application

High entropy materials are attracting ever-increasing concern on account of their unique structure and unprecedented potential application in various fields. In this letter, a high entropy (Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)₃O₄ (S-HEO) with Fd3m spinel structure, is prepared by solid-state reaction. Importantly, without the presence of entropy stabilization behavior, single spinel-structure of S-HEO can be retained through the re-heat treatment process. Benefiting from abundant electroactive species and various chemical valance, excellent Li⁺ storage capability and favorable performance toward oxygen evolution reaction (OER) are achieved with S-HEO. As anode material for Li ion batteries, S-HEO presents a high specific capacity of 560 mAh g⁻¹ at 100 mA g⁻¹ and superior capacity retention of 100% after 5000 cycles. In-situ EIS, ex-situ TEM and XRD analysis were conducted to probe insight into the diffusion kinetic and structural evolution of S-HEO upon cycling. Efficient water oxidation with an overpotential of 332 mV to reach 10 mA cm⁻² are achieved with S-HEO. With comparison to spinel-type moderate entropy oxides (S-MEOs), the synergic effect between five species highlight the merits of high-entropy feature, manifesting a better OER kinetic and higher stability in KOH solution. This research demonstrates the significant importance of high-entropy concept to boost the performance of high entropy materials for electrochemical application.