Quantum-Size FeS2 with Delocalized Electronic Regions Enable High-Performance Sodium-Ion Batteries Across Wide Temperatures

Quantum-scaled FeS 2 induces delocalized electronic regions, effectively reducing electrostatic potential barriers and accelerating Na + diffusion kinetics. The free charge accumulation regions were formed by edge mismatched atoms, activating numerous electrochemically sites to enable high-capacity Na + storage and ultrafast-ion transport across wide temperature range (−35 to 65 °C). The FeS 2 QD/MXene anode delivers superior wide-temperature capacity of 255.2 mAh g −1 (−35 °C) and 424.9 mAh g −1 (65 °C) at 0.1 A g −1 . The FeS 2 QD/MXene//NVP cell achieves a record energy density of 162.4 Wh kg⁻ 1 at − 35 °C.