High-entropy strategy suppresses anion redox to boost high-performance biphasic layered oxide cathodes for sodium-ion batteries

Layered oxide materials garner extensive attention owing to their high specific capacity and straightforward synthesis, yet their cycling stability requires improvement. Particularly when anions participate in redox reactions, although additional capacity gains are possible, this occurs at the expense of poor cycling stability. To address this issue, a combined approach of biphasic structure regulation and a high-entropy strategy is proposed to suppress anion redox and enhance cycling stability. Experimental results demonstrate that applying this strategy increased the specific capacity of the cathode material from 120 to 132 mAh g⁻¹ at 100 mA g⁻¹ , with capacity retention rising from 79.1 % to 90.1 % after 100 cycles. At 10 mA g⁻¹ , the specific capacity increased from 133 to 157 mAh g⁻¹ . Testing results indicate that biphasic structure regulation modulates the Na-layer spacing, facilitates Na⁺ migration, reduces lattice damage, and enhances rate capability and cycling stability. The high-entropy strategy suppresses the participation of (O₂)^n- species in redox processes by altering local electronic states, thereby improving cycling stability while activating redox couples to enhance specific capacity. The synergistic application of biphasic structure regulation and high-entropy strategy proposed in this study offers novel perspectives for developing high-performance layered oxide materials.