High-entropy oxides as advanced anode materials for long-life lithium-ion Batteries

High-Entropy Oxides (HEOs) are a novel type of perspective anode materials for lithium ion batteries (LIBs), owing to their stable crystal structure and high theoretical capacity. However, the understanding of their intrinsic crystal structure and lithium storage mechanism is relatively shallow, hindering their further development and application. In this work, (FeCoNiCrMn)3O4 HEO was prepared successfully by the oxidation of high-entropy FeCoNiCrMn alloy powders, and was applied as a new advanced anode material for LIBs. The as-prepared (FeCoNiCrMn)3O4 HEO exhibited excellent cycle stability, and achieved a high reversible capacity of 596.5 mA h g−1 and a good capacity retention of 86.2% after 1200 cycles at 2.0 A g−1. Such long cycle stability can be ascribed to its special crystal structure and narrow band gap, which was verified by density functional theory (DFT) calculations. During the first cycle of lithium insertion, (FeCoNiCrMn)3O4 HEO gradually transformed into fine crystals below the XRD detection threshold, which was confirmed by in situ XRD. Our results demonstrate that high-entropy makes (FeCoNiCrMn)3O4 HEO possess a stable structure and narrow band gap, and three-dimensional spinel structure provides a channel for ion transport. This points out the direction for the preparation of HEOs with stable structure and excellent performance, and provides a promising candidate for anode materials of LIBs.