Computational Discovery of Metastable NaMnO$_2$ Polymorphs as High-Performance Cathodes with Ultralow Na$^+$ Migration Barriers
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| Format: | Preprint |
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2025
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| _version_ | 1866918067512016896 |
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| author | Wang, Fukuan Zhou, Chen Wang, Busheng Liu, Yong |
| author_facet | Wang, Fukuan Zhou, Chen Wang, Busheng Liu, Yong |
| contents | Using an ab initio evolutionary algorithm combined with first-principles calculations, two metastable NaMnO$_2$ polymorphs, $I4_1/amd$ and Cmcm, are identified as promising cathode materials for sodium-ion batteries. Both phases exhibit excellent thermodynamic stability, lying within 35~meV/atom of the ground-state \textit{Pmmn} phase across 0--50~GPa, and are dynamically and thermally stable under ambient conditions following high-pressure synthesis, as confirmed by phonon and ab initio molecular dynamics simulations. During desodiation, a Jahn--Teller-induced magnetic transition enhances Mn--O hybridization, reduces the bandgap, and promotes robust charge compensation and oxygen retention. Remarkably, the Cmcm phase achieves record-low Na$^+$ migration barriers (0.39~eV at high Na concentration; 0.27~eV at low concentration), representing 47\% and 36\% reductions respectively compared to conventional $C2/m$, while delivering a higher average voltage (3.19~V vs 2.88~V). The $I4_1/amd$ phase exhibits concentration-dependent diffusion with a low-energy pathway (0.38~eV) and maintains competitive voltage (2.94~V). These findings suggest that metastable NaMnO$_2$ polymorphs may offer viable alternatives to conventional cathode materials, particularly where fast ionic conduction is required. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_17866 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Computational Discovery of Metastable NaMnO$_2$ Polymorphs as High-Performance Cathodes with Ultralow Na$^+$ Migration Barriers Wang, Fukuan Zhou, Chen Wang, Busheng Liu, Yong Materials Science Using an ab initio evolutionary algorithm combined with first-principles calculations, two metastable NaMnO$_2$ polymorphs, $I4_1/amd$ and Cmcm, are identified as promising cathode materials for sodium-ion batteries. Both phases exhibit excellent thermodynamic stability, lying within 35~meV/atom of the ground-state \textit{Pmmn} phase across 0--50~GPa, and are dynamically and thermally stable under ambient conditions following high-pressure synthesis, as confirmed by phonon and ab initio molecular dynamics simulations. During desodiation, a Jahn--Teller-induced magnetic transition enhances Mn--O hybridization, reduces the bandgap, and promotes robust charge compensation and oxygen retention. Remarkably, the Cmcm phase achieves record-low Na$^+$ migration barriers (0.39~eV at high Na concentration; 0.27~eV at low concentration), representing 47\% and 36\% reductions respectively compared to conventional $C2/m$, while delivering a higher average voltage (3.19~V vs 2.88~V). The $I4_1/amd$ phase exhibits concentration-dependent diffusion with a low-energy pathway (0.38~eV) and maintains competitive voltage (2.94~V). These findings suggest that metastable NaMnO$_2$ polymorphs may offer viable alternatives to conventional cathode materials, particularly where fast ionic conduction is required. |
| title | Computational Discovery of Metastable NaMnO$_2$ Polymorphs as High-Performance Cathodes with Ultralow Na$^+$ Migration Barriers |
| topic | Materials Science |
| url | https://arxiv.org/abs/2506.17866 |