Anchoring carbonyl-driven electron delocalization enables wide-temperature hard carbon anodes for sodium-ion...

The application of hard carbon in sodium-ion batteries is limited by sluggish reaction kinetics, limited capacity and restricted operating temperature ranges. Herein, the anchoring carbonyl-driven electron delocalization strategy is originally proposed to simultaneously address the above issues. This strategy can effectively balance the dual mechanisms of reversible surface adsorption and intercalation of carbon layers, while simultaneously mitigating irreversible adsorption from restricted ion diffusion at low temperatures and enhancing interfacial stability along with charge transfer kinetics. Specifically, the anchoring of highly electronegative carbonyl groups coupled with synergistic doping engineering enhances electronic delocalization within hard carbon and expands its interlayer spacing, thereby facilitating efficient and rapid sodium storage in hard carbon anodes. As a result, the advanced hard carbon anodes deliver remarkable cycling stability (over 6200 cycles at 5.0 A g^-1) and extreme operating temperatures (-50 to 60 °C). When paired with Na₃V₂(PO₄)₃ cathode, the full cells retain capacity retention of 93.3% and 96.6% after 2900 and 1200 cycles at -25 and -45 °C, respectively. Moreover, high-quality thick-electrode pouch cells demonstrate stable cycling performance over 130 cycles at -25 °C. This approach provides new insights for wide-temperature sodium-ion batteries.