Exploring the role of spin polarization in enhancing sodium storage capabilities of two-dimensional transition metal thiophosphites

Two-dimensional ternary transition metal thiophosphites (MPS 3 ), as an emerging class of anode candidates for sodium ion batteries (SIBs), exhibit tremendous application potential. This study focuses on a series of 2D MPS 3 materials containing different transition metal elements (M = Mn, Fe, Co, and Ni) synthesized by the chemical vapor transport method. In-depth theoretical analysis employing density functional theory combined with crystal orbital Hamilton population reveals that NiPS 3 exhibits the lowest Na + diffusion barrier and the strongest Na + adsorption capability among the four materials. And these exceptional characteristics originate from the distinctive low-spin electronic configuration inherent in NiPS 3 , triggering a pronounced electronic repulsion between bridging Ni and S atoms, consequently diminishing the strength of Ni-S bonds and substantially enhancing the electrochemical reactivity. Furthermore, the S element in NiPS 3 exhibits a highest p-band center energy level in the four samples, resulting in a corresponding decrease in the occupancy of the Na-S antibonding sigma orbital, which in turn strengthens the interaction between S and Na + . This enhanced interaction significantly improves the adsorption capability of NiPS 3 towards Na + , effectively facilitating the charge transfer at the interface. Electrochemical test results indicate that NiPS 3 exhibits the most superior electrochemical performance among the four materials, maintaining a specific capacity of 500.7 mA h g −1 after 1100 cycles at 5 A g −1 . This study, through the profound integration of theory and experiments, fundamentally elucidates and verifies the underlying reasons for the superior properties of NiPS 3 in MPS 3 anodes.