Tailoring Nitrogen Terminals on MXene Enables Fast Charging and Stable Cycling Na-Ion Batteries at Low Temperature.

Sodium-ion batteries stand a chance of enabling fast charging ability and long lifespan while operating at low temperature (low-T). However, sluggish kinetics and aggravated dendrites present two major challenges for anodes to achieve the goal at low-T. Herein, we propose an interlayer confined strategy for tailoring nitrogen terminals on TiC MXene (TiC-N) to address these issues. The introduction of nitrogen terminals endows TiC-N with large interlayer space and charge redistribution, improved conductivity and sufficient adsorption sites for Na, which improves the possibility of TiC for accommodating more Na atoms, further enhancing the Na storage capability of TiC. As revealed, TiC-N not only possesses a lower Na-ion diffusion energy barrier and charge transfer activation energy, but also exhibits Na-solvent co-intercalation behavior to circumvent a high de-solvation energy barrier at low-T. Besides, the solid electrolyte interface dominated by inorganic compounds is more beneficial for the Na transfer at the electrode/electrolyte interface. Compared with of the unmodified sample, TiC-N exhibits a twofold capacity (201 mAh g), fast-charging ability (18 min at 80% capacity retention), and great superiority in cycle life (80.9%@5000 cycles) at - 25 °C. When coupling with NaV(PO)F cathode, the TiC-N//NVPF exhibits high energy density and cycle stability at - 25 °C.