Achieving Zero Phase Transition in P2-Type Layered Oxides via Targeted Chemical Design for Zero-Strain Sodium Storage.
basic_science · Level V
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- Record sourced from PubMed, PMID 42057554.
- Also identified by DOI 10.1002/adma.202521716.
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Abstract
P2-type layered oxide cathodes dominate sodium-ion batteries (SIBs) due to exceptional sodium ion kinetics. However, longstanding phase transitions (e.g., P2-to-O2) not only compromise this inherent kinetic advantage but also cause severe stress strain undermining structural stability. Here, we propose a stage-specific chemical design that targetly addresses de-sodiated interlayer O<sup>2-</sup> repulsion, the structural origin of phase transitions in P2 cathodes. The designed Na<sub>0.67</sub>Ni<sub>0.05</sub>Fe<sub>0.05</sub>Ti<sub>0.05</sub>Cu<sub>0.2</sub>Mn<sub>0.65</sub>O<sub>2</sub> (NFTCM) cathode shows a record Na-layer spacing (3.67 Å) with reduced negative charge on oxygen ions, maximally lowering O<sup>2-</sup>-O<sup>2-</sup> repulsion during the entire desodiation process. As evidenced by in situ X-ray diffraction, the NFTCM cathode shows a true zero-phase-transition behavior with a record-low volume variation of 0.062% upon cycling. This stable, zero-strain Na ions storage behavior contributes to exceptional rate capability (121 mA h/g at 10C) and remarkably stable cycling, retaining 93.7% capacity after 600 cycles. Furthermore, operando neutron diffraction data indicate that the eliminated phase transition also enables a robust oxygen framework, a crucial factor in stabilizing the ion storage process of layered oxides.