High-Entropy Phase Stabilization Engineering Enables High-Performance Layered Cathode for Sodium-Ion Batteries

O3-type layered oxides are considered as one of the most promising cathode materials for rechargeable sodium-ion batteries (SIBs) due to their appealing energy density and feasible synthesis. Nevertheless, it undergoes complicated phase transitions and pronounced structural degradation during the cycling of charge/discharge process, rendering severe volumetric strain and poor cycling performance. Herein, a zero-strain high-entropy NaNi0.2Fe0.2Mn0.35Cu0.05Zn0.1Sn0.1O2 cathode for SIBs is presented by high-entropy phase stabilization engineering. It is verified that this low-nickel cobalt-free high-entropy cathode can deliver a highly reversible phase evolution, zero volumetric strain, and a significantly improved cycling performance in full cells (87% capacity retention after 500 cycles at 3.0 C). Combining X-ray absorption spectra and first-principles calculations, the varied elemental functions in the high-entropy framework are clearly elucidated, namely, Ni/Fe/Cu acts as charge compensators, while Mn/Zn/Sn serve as interlayer slipping inhibitors through enhanced charge localization besides their stable valence states. By addressing the volumetric strain and cycling instability concerns for O3-type cathode materials, this work presents a promising strategy for inhibiting irreversible phase transitions and structural degradation in intercalation electrodes, which significantly boosts the development of commercially feasible cathodes for high-performance SIBs. A zero-strain layered cathode for sodium-ion batteries is presented by high-entropy phase stabilization engineering. By solving the drastic volumetric strain and cycling instability concerns for O3-type cathode materials, this low-nickel cobalt-free high-entropy cathode delivers highly reversible phase transition, zero volumetric strain, and significantly improved cycling stability. image