One-step molten salt synthesis of high entropy oxides

High-entropy oxides (HEOs) have received widespread attention owing to their tunable properties and vast composition spaces. However, the universal synthesis of HEOs with high purity still faces challenge. In this work, a one-step molten salt method is reported for the synthesis of phase-pure rock salt-type (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O. When used as an anode material for lithium-ion batteries, (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O exhibits high specific capacity and cycling stability, maintaining a capacity retention of 94% after 220 cycles (0.2 A g−1). The superior performance can be attributed to accelerated electron and ion transport as well as enhanced Li adsorption/coupling induced by internal defects. To further demonstrate the wide applicability of the molten salt method, single-phase spinel and pyrochlore HEOs are also successfully synthesized. The presented molten salt method, with its ease of operation, homogeneous reaction environment and low synthesis temperatures, makes it an ideal synthesis technique for the development of novel HEO powders, especially for electrode materials.