Screening Na-Excess Cation-Disordered Rocksalt Cathodes with High Performance.
basic_science · Level V
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- Record sourced from PubMed, PMID 39462844.
- Also identified by DOI 10.1021/acsnano.4c09285.
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Abstract
The practical application of Na-ion cathode materials is currently restricted by their low energy density and sluggish dynamics, while the cation-disordered rocksalt (DRX) structures offer a possible solution to the challenge. In this study, among the 24 candidates containing <i>d</i><sup>0</sup> elements, we use mixing temperature as a descriptor to screen the synthesizable Na-excess DRX, and we have identified Na<sub>1.2</sub>Mn<sub>0.4</sub>Mo<sub>0.4</sub>O<sub>2</sub> as the most promising candidate that exhibits a Na percolating fraction of 53%, which is higher than that of Li<sub>1.2</sub>Mn<sub>0.4</sub>Ti<sub>0.4</sub>O<sub>2</sub> (35%) proposed in the previous study due to the larger lattice constant in Na-excess DRX cathodes. More importantly, Na<sub>1.2</sub>Mn<sub>0.4</sub>Mo<sub>0.4</sub>O<sub>2</sub> is predicted to have a capacity of 228 mAh/g with an energy density of 552 Wh/kg derived from percolation theory and cluster-expansion Monte Carlo simulations, which is higher than that of Na<sub>1.3</sub>Nb<sub>0.3</sub>Mn<sub>0.4</sub>O<sub>2</sub> and Na<sub>1.14</sub>Mn<sub>0.57</sub>Ti<sub>0.29</sub>O<sub>2</sub> synthesized recently. For a better understanding, the redox mechanism is explored, which involves Mo<sup>4+</sup>/Mo<sup>6+</sup>, Mn<sup>3+</sup>/Mn<sup>4+</sup>, and O<sup>2-</sup>/O<sup>n-</sup> (0 < <i>n</i> < 2), indicating the participation of anionic redox. Meanwhile, the Na<sup>+</sup> diffusion prefers a divacancy mechanism via an o-t-o diffusion channel with a low diffusion barrier of 0.29 eV. This study expands the family of DRX for the cathode of Na-ion batteries with enhanced performance.