Boosting Sodium Storage in 2D Phosphorene/Ti3C2Tx MXene Nanoarchitectures with Stable Fluorinated Interphase.

The stacking of complementary 2D materials into hybrid architectures is desirable for batteries with enhanced capacity, fast charging and long lifetime. However, the 2D heterostructures for energy storage are still underdeveloped, and some associated problems like low Coulombic efficiencies need to be tackled. Herein, we reported a phosphorene/MXene hybrid anode with an in situ formed fluorinated interphase for stable and fast sodium storage. The combination of phosphorene nanosheets with Ti3C2Tx MXene not only facilitate the migration of both electrons and sodium cations but also alleviate structural expansion of phosphorene and thereby improve the cycling performance of the hybrid anode. XPS in-depth analysis reveals that the fluorine terminated MXene stabilize the solid electrolyte interphase by forming a fluorine-rich layer on the anode surface. DFT calculations confirm that the sodium affinities and diffusion kinetics are significantly enhanced in the phosphorene/MXene heterostructure, particularly in the phosphorene/Ti3C2F2. As a result, the hybrid electrode achieved a high reversible capacity of 535 mAh g-1 at 0.1 A g-1 and superior cycling performance (343 mAh g-1 after 1000 cycles at 1 A g-1 with a capacity retention of 87%) in a fluorine-free carbonate electrolyte.