A novel rock-salt structure high-entropy oxide Fe <sub>0.2</sub>Co <sub>0.2</sub>Ni <sub>0.2</sub>Cu <sub>0.2</sub>Zn <sub>0.2</sub>O as a highly reversible lithium storage material
Xiaobin He, Xuemei Zeng, Wei Wang, Yaqing Guo, Shengjie Zheng, Yun Li, Guang Mo, Jiatong Zhang, Shun Wang, Hao Wang, Yifei Yuan
Abstract
High-entropy oxides (HEOs) composed of multiple metal elements have garnered significant attention as anode materials for lithium-ion batteries (LIBs), owing to their synergistic effects between constituent metal oxides and broad material design flexibility. However, the advancement of HEOs in LIBs has been hindered by time-consuming synthesis methods, complex fabrication procedures, and an insufficient understanding of their lithium storage mechanisms. In this study, a rock-salt structure HEO Fe<sub>0.2</sub>Co<sub>0.2</sub>Ni<sub>0.2</sub>Cu<sub>0.2</sub>Zn<sub>0.2</sub>O was ultrafast synthesized by the Joule heating technique within 3 seconds and was applied to LIBs for the first time as a conversion-type anode material. The material exhibits not only excellent capacity retention but also remarkable structural reversibility. Specifically, the reversible capacity is determined to be 1310 mAh g<sup>-1</sup> for 200 cycles at 0.1 A g<sup>-1</sup>, and 705 mAh g<sup>-1</sup> for 3000 cycles at 5 A g<sup>-1</sup>. Detailed mechanistic investigations reveal that ZnO serves as an electrochemically inactive structural stabilizer that maintains the rock-salt framework, while Cu<sup>2+</sup> is difficult to oxidize back to its original state once reduced to Cu<sup>0</sup>. This study provides critical insights into the composition-structure-property relationships of HEOs, offering valuable guidance for designing high-performance LIBs anode materials through entropy engineering.