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 Ti₃C₂ MXene (Ti₃C₂-N_funct) to address these issues. The introduction of nitrogen terminals endows Ti₃C₂-N_funct with large interlayer space and charge redistribution, improved conductivity and sufficient adsorption sites for Na⁺, which improves the possibility of Ti₃C₂ for accommodating more Na atoms, further enhancing the Na⁺ storage capability of Ti₃C₂. As revealed, Ti₃C₂-N_funct 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, Ti₃C₂-N_funct exhibits a twofold capacity (201 mAh g^-1), 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 Na₃V₂(PO₄)₂F₃ cathode, the Ti₃C₂-N_funct//NVPF exhibits high energy density and cycle stability at - 25 °C.