Design of high-entropy P2/O3 hybrid layered oxide cathode material for high-capacity and high-rate sodium-ion batteries

High-entropy layered cathode materials have garnered significant attention due to their exceptional structural stability and capacity retention. However, the complex composition of these materials has posed challenges for performance optimization. Herein, an innovative high-entropy P2/O3 hybrid layered oxide cathode material with impressive reversible capacity and high-rate capabilities is designed according to the configurational entropy adjustment strategy. Specifically, the unique structure of Na0.85Li0.05Ni0.3Fe0.1Mn0.5Ti0.05O2 (LNFMT) exhibits not only enhanced anionic activity but also mitigated migration of transition metals at high voltage. The high-entropy effect facilitates the migration of Li+ to Na layer, forming a pseudo-tetrahedral structure that hinders the movement of Fe3+. Additionally, the robust Ti-O bond ensures the internal cohesion of transition metal layers, enhancing the structural stability during de-/intercalation processes. As a result, the undesirable P2-O2 phase transformation is effectively suppressed in 1.5-4.5 V, leading to a remarkable capacity retention of over 70% after 100 cycles at 0.2 C. Moreover, LNFMT shows a high discharge capacity of 116 mAh/g at 10 C with excellent capacity retention of 94.23% after 150 cycles in 2.0-4.2 V, demonstrating its superior rate capability. This research showcases the significant impact of the high-entropy effect and provides a novel perspective for the design of sodium-ion cathode materials.