Fast synthesis of high-entropy oxides for lithium-ion storage

High-entropy oxides (HEOs) have been considered conspicuous battery materials due to their tunable properties and stable crystal structure. In this work, several kinds of high entropy oxides (HEOs) are prepared by an ultra-fast Joule heating method in several seconds. This simple and effective method enhances the efficiency of near four orders of magnitude than that of the common sintering methods. As anode materials of lithium-ion batteries (LIBs), they have considerable rate capacity and cycling stability. For example, quinary (MgCoNiCuZn)O HEO delivers a high capacity of ∼150 mAh g−1 even at ultrahigh current density of 10 A g−1 and cycle stability up to 2,600 cycles. By in-situ transmission electron microscopy, the full lithiation/de-lithiation process is tracked down to the atomic scale in real time, observing the distinct reaction dynamics and structural evolutions in rock-salt-type (MgCoNiCuZn)O during cycling. Conversion/alloying reaction kinetics are identified by the disappearance of the original rock-salt phase and the formation of polyphase with the intercalation of lithium-ions. While upon de-lithiation, the post-lithiation polyphase state can be recovered to the original rock-salt-structured (MgCoNiCuZn)O. Our work provides valuable guidelines to high-efficient synthesis and mathematical understanding of lithium storage mechanisms of HEOs for next-generation long-life energy storage.