Phase-Transition Engineering Enables Low-Strain Cathodes for 192 Wh kg<sup>-</sup> <sup>1</sup> Sodium-Ion Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 42517694.
- Also identified by DOI 10.1002/adma.74333.
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Abstract
Phase transitions in sodium layered transition metal (TM) oxides often induce microstrain and TM ion migration, leading to structural degradation and poor cycling stability. However, a rational design approach for optimizing phase transitions is still lacking. Here we introduce phase transition potential (Φ<sub>phase</sub>) as a rational descriptor to predict and control phase evolution in these cathodes. A lower Φ<sub>phase</sub> enables smoother Na<sup>+</sup> migration and slower slab sliding during Na extraction, thereby facilitating a continuous phase transformation rather than abrupt phase changes. Guided by this concept, we design a calcium-substituted layered oxide, Na<sub>0.96</sub>Ca<sub>0.02</sub>Ni<sub>0.33</sub>Fe<sub>0.33</sub>Mn<sub>0.33</sub>O<sub>2</sub> (NCNFMO), which delivers a specific capacity of 140 mAh g<sup>-1</sup> at 0.1 C and retains 84.2% of its initial capacity after 500 cycles at 1 C, compared to only 26.4% retention for NaNi<sub>0.33</sub>Fe<sub>0.33</sub>Mn<sub>0.33</sub>O<sub>2</sub>. Moreover, the NCNFMO||Al@C full cell maintains a high-capacity retention of 82.5% after 100 cycles, and 6.1 Ah full cell demonstrates an energy density of 192 Wh kg<sup>-1</sup> <sub>entire cell</sub>. These findings offer fundamental insights into phase behavior-induced microstrain and a promising path toward high-energy, long-life sodium-ion batteries.