Layered Phosphorus-Rich Phosphide Composite as a Stable, High-Capacity Anode for Sodium Ion Batteries

Layered phosphide materials with attractive capacity have been considered to be promising cathode and anode candidates for high-specific-energy sodium ion batteries due to their high capacitance and energy density. The main challenge for the practical application of such materials is the poor structural stability during sodium ion insertion and extraction. In this work, a new material, Cu0.75Sn1.25P14, is investigated for the first time as an anode material for sodium ion batteries (NIBs). A feasible electrostatic spinning method is used to fabricate hollow Cu0.75Sn1.25P14@C composite materials under natural conditions. Moreover, on the basis of density functional theory (DFT) calculations, it is shown that Cu0.75Sn1.25P14 possesses a two-dimensional layered tubelike structure, different from those of layered graphite or black phosphorus and highly stable with a melting point more than 1000 K higher than those of Sn and P. Tested as anode materials for NIBs, Cu0.75Sn1.25P14 can deliver an unexpectedly high reversible capacity surpassing 1000 mA h g–1 and long cycle stability with 200 cycles, in addition to good rate capability and coulombic cycle efficiency. Finally, DFT calculations confirm that Cu atoms dispersed in the phosphide not only contribute to an increase in capacity but also are favorable for enhancing electrochemical performance. These results demonstrate the potential applications of Cu0.75Sn1.25P14 as new electrode materials in next-generation high-specific-energy NIBs.