Phase Engineering of MXene Derivatives Via Molecular Design for High‐Rate Sodium‐Ion Batteries.

Since 2019, research into MXene derivatives has seen a dramatic rise; further progress requires a rational design for specific functionality. Herein, through a molecular design by selecting suitable functional groups in the MXene coating, we have implemented the dual N doping of the derivatives, nitrogen‐doped TiO2@nitrogen‐doped carbon nanosheets (N‐TiO2@NC), to strike a balance between the active anatase TiO2 at low temperatures, and carbon activation at high temperatures. The NH3 reduction environment generated at 400 °C as evidenced by the in situ pyrolysis SVUV‐PIMS process is crucial for concurrent phase engineering. With both electrical conductivity and surface Na+ availability, the N‐TiO2@NC achieves higher interface capacitive‐like sodium storage with long‐term stability. More than 100 mAh g−1 is achieved at 2 A g−1 after 5000 cycles. The proposed design may be extended to other MXenes and solidify the growing family of MXene derivatives for energy storage. [ABSTRACT FROM AUTHOR]