Lattice distortion induced rock salt high-entropy oxide for high-rate lithium-ion storage

High entropy oxides (HEOs) have garnered increasing attention as novel anode materials for high-performance lithium-ion batteries (LIBs) owing to their high structural stability and ideal element tunability. However, the defect engineering for boosting the electrochemical performance remains a major challenge. In this study, lattice distortion modulation is implemented through low-temperature post-processing strategy (post-annealed at 723 K for different times) on rock-salt-type (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O to boost its Li+ storage performance. It can be concluded that lattice distortion induces suitable amounts of oxygen-vacancies, thereby enhancing intrinsic conductivity and facilitating electron/ion migration kinetic. Thus, the optimal CCNMZ-10 (post-annealed at 723 K for 10 min) electrode exhibits an impressive reversible capacity of 993 mAh g-1 at 200 mA g-1 after 150 cycles, superior rate capability (66.3% capacity retention from 100 to 3000 mA g-1), and outstanding high-rate capacity of 771 mAh g-1 after 400 cycles at 1000 mAh g-1. Meanwhile, it also delivers an ultra-high pseudocapacitive contribution of 92.7% at 1 mV s-1. This work demonstrates a promising strategy to effectively enhance the electrochemical performance of HEOs through lattice distortion defects, and also opens new perspectives on the development of defect-rich HEO anode materials.