Creating an Air-Stable Sulfur-Doped Black Phosphorus-TiO2 Composite as High-Performance Anode Material for Sodium-Ion Storage

With the increasing demand for low cost, long lifetime, high energy density storage systems, an extensive amount of effort has recently been focused on the development of sodium-ion batteries (SIBs), and a variety of cathode materials have been discovered. However, looking for the most suitable anode material for practical application is a major challenge for SIBs. Herein, a high capacity sulfur-doped black phosphorus-TiO2 (TiO2-BP-S) anode material for SIBs is first synthesized by a feasible and large-scale high-energy ball-milling approach, and its stability in air exposure is investigated through X-ray photoelectron spectroscopy. The morphology of TiO2-BP-S is characterized using transmission electron microscopy, indicating that the TiO2 nanoparticles produce PTi bonds with BP. The TiO2-BP-S composite with PS and PTi bonds exhibits excellent stability in air and the superior electrochemical performance. For example, the discharge specific capacity is up to 490 mA h g(-1) after 100 cycles at 50 mA g(-1), and it remains at 290 mA h g(-1) after 600 cycles at 500 mA g(-1). Meanwhile, the scientific insight that the formation of stable PS and PTi bonds can provide a guide for the practical large-scale application of SIBs in other titanium base and black phosphorus materials is looked forward.