Black Phosphorus Stabilizing Na₂Ti₃O₇/C Each Other with an Improved Electrochemical Property for Sodium-Ion Storage

Sodium-ion batteries have increasingly been considered as an attractive alternative to lithium-ion batteries for large-scale applications. High specific capacity and suitable working potential anode materials are one of the keys to search for future developments. Here, a novel and stable sodium titanate/carbon-black phosphorus (NTO/C-BP) hybrids are first fabricated as a promising anode material for advanced sodium-ion batteries. Under the protection of argon (Ar) atmosphere, the direct high-energy mechanical milling of the BP nanoparticle and NTO/C results in the formation of NTO/C-BP hybrids. In other words, the BP nanoparticle can be interconnected with bare NTO by P-O-Ti bonds and/or form stable P-C bonds with the carbon coating layer on the surface of NTO. The NTO/C-BP hybrids are not only beneficial for enhancing specific capacity but also have a great protective effect on the exposure of BP to air by the synergistic effect between BP and NTO/C. The results show that the NTO/C-BP hybrids can deliver very high specific capacity (∼225 mA h g^-1 after 55 cycles at 20 mA g^-1, ∼183 mA h g^-1 after 100 cycles at 100 mA g^-1). It is expected from these scientific findings that forming stable P-C bonds and P-O-Ti bonds in this work can serve as a guidance to other Ti-based and P-based electrode materials for practical large-scale application of sodium-ion batteries.