Three-pronged strategy of high-entropy, P2/O3 biphasic structure and Li doping approaches to construct high-performance sodium-ion batteries cathode

Layered metal oxides have attracted significant research interest as potential cathode materials for sodium-ion batteries (SIBs), primarily owning to their excellent energy density characteristics and economic viability. Nonetheless, the durability of these materials is limited due to irreversible phase transformations and redox reactions involving lattice oxygen, especially under high-voltage conditions. This results in progressive structural collapse and accelerated capacity degradation. In this study, an innovative three-in-one design approach that combines "high-entropy, dual-phase and Li doping" for layered cathodes is proposed. The study elucidates that the combination of a dual-phase and high-entropy structure effectively improves structural integrity and cycling stability. Furthermore, Li doping promotes the redox reaction of cationic ions and facilitates charge compensation, thereby improving the capacity. The prepared cathode material, P2/O3-Na 0.7 Mn 0.4 Ni 0.27 Li 0.03 Cu 0.1 Fe 0.1 Ti 0.1 O 2 , delivers a high capacity of 139 mAh g −1 , stable cycling capability, superior rate performance (79.1 mAh g −1 at 2000 mA g −1 ) and enhanced air stability. In a full cell configuration combining a high-entropy cathode and a hard carbon anode, outstanding electrochemical performance is demonstrated, with a capacity of 138.4 mAh g −1 and an energy density of 410 Wh kg −1 . This work proposes a novel design strategy for high-performance SIBs.