2025/06/22 by Wang, Fukuan, Zhou, Chen, Wang, Busheng +1
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)
paper · doi:10.48550/arxiv.2506.17866
Using an ab initio evolutionary algorithm combined with first-principles calculations, two metastable NaMnO2 polymorphs, I41/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 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 I41/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 NaMnO2 polymorphs may offer viable alternatives to conventional cathode materials, particularly where fast ionic conduction is required.