Hierarchical MXene‐Derived NTP/C Nanohybrids for Cryogenic Sodium‐Ion Batteries

ABSTRACT Sodium‐ion batteries (SIBs) are attractive for large‐scale energy storage owing to sodium abundance and low cost, yet their deployment in cold environments is severely hindered by sluggish Na + kinetics, poor electronic conductivity of anode materials, and electrolyte solidification leading to impedance rise at sub‐zero temperatures. Here, we report an integrated electrode–electrolyte strategy that enables reliable sodium‐ion storage down to −40°C. A hierarchical NaTi 2 (PO 4 ) 3 /C (NTP/C) nanohybrid is synthesized via in situ oxidative phosphate conversion of Ti 3 C 2 T x MXene, yielding ultrasmall NASICON‐type NTP domains uniformly anchored on a conductive, carbide‐derived carbon framework. This hybrid architecture establishes continuous ion–electron percolation networks, suppresses interfacial polarization, and promotes dominant pseudocapacitive charge storage (∼82% at 0.7 mV s −1 ), while maintaining favorable Na + diffusivities. Coupling the NTP/C anode with a low‐viscosity ether‐based electrolyte preserves ionic conductivity and forms an inorganic‐rich, NaF‐stabilized solid electrolyte interphase (SEI) at low temperature, further mitigating kinetic and interfacial limitations. As a result, the cell delivers 150 mAh g −1 at −40°C (0.1 C), retains ∼110 mAh g −1 at 0.5 C, and exhibits excellent long‐term stability. This work demonstrates a generalizable MXene‐derived design paradigm for SIBs and provides mechanistic insights into cryogenic ion storage, thereby advancing sodium‐based energy systems for extreme‐environment applications.