Entropy Stabilization Effect and Oxygen Vacancies Enabling Spinel Oxide Highly Reversible Lithium-Ion Storage.

High-entropy materials are an emerging kind of solid-solution material, demonstrating various exotic physicochemical properties, that have led to increased research activity as electrode materials for rechargeable batteries. Here, a kind of high-entropy spinel oxide, (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4 (CCFMNO), was successfully fabricated via a solution combustion method. Due to the entropy stabilization effect and the intrinsic high mechanical strength of CCFMNO, an excellent cycling stability can be achieved. In addition, the fruitful oxygen vacancies in CCFMNO increase extra Li-ion accommodation sites, accelerating electronic conductivity and promoting Li-ion migration, thus enabling a high rate performance of 428 mAh g-1 at a high current density of 10 A g-1. More impressively, CCFMNO electrodes demonstrate excellent temperature adaptability with no capacity degeneration after 50 cycles at 0, 25, and 50 °C. Meanwhile, a full cell based on a CCFMNO anode and LiFePO4 cathode delivers an impressive high energy density of 372 Wh kg-1. All these impressive lithium storage performances strongly suggest that CCFMNO could be a promising anode material for lithium-ion batteries.