High entropy spinel oxide nanoparticles for superior lithiation-delithiation performance

High entropy spinel oxide (HESO) nanoparticles were synthesizedviaa surfactant-assisted hydrothermal method and used as a novel anode material in a lithium-ion battery. The HESO consists of non-equimolar cations of Cr, Mn, Fe, Co, and Ni dispersed in two Wyckoff sites with various valence states. Due to a strong entropy-induced phase stabilization effect of the HESO, no inactive MgO structural pillars, which are exclusively present in the reported rock salt type high entropy oxides, are required to achieve high electrode cycling stability. A superior charge-discharge capacity of 1235 mA h g⁻¹, the highest among all known HEOs, is obtained with 90% capacity retention after 200 cycles. The unique HESO is also characterized by plenty of oxygen vacancies and three-dimensional Li⁺transport pathways. Also, great high-rate performance,i.e., 500 mA h g⁻¹@ 2000 mA g⁻¹, of the HESO electrode is demonstrated.