Dual-Doped Hematite Nanorod Arrays on Carbon Cloth as a Robust and Flexible Sodium Anode

Rechargeable batteries with flexibility can find tremendous applications in wearable and bendable electronics. One central mission for the advancement of such high-performance batteries is the exploration of flexible anodes with electrochemical and mechanical robustness. Herein reported is a robust and flexible sodium-ion anode based on self-supported hematite nanoarray grown on carbon cloth. The ammonia treatment that results in dual doping of both nitrogen and low-valent iron renders surface reactivity and electric conductivity to the material. The dual-doped hematite arrays afford a robust activity for sodium storage, exhibiting reversible capacities of 895 and 382 mAh g(-1) at current rates of 0.1 and 5 A g(-1), respectively, or 615 and 356 mAh g(-1) by removing the contribution of the substrate. They also sustain 85% of the initial capacity upon 200 cycles at 0.2 A g(-1). To demonstrate the flexibility, full cells composed of a hematite array anode and Na3V2(PO4)(3)/C cathode are assembled. The cell is capable of affording an energy density of 201 Wh kg(-1) and sustaining repeated bending without performance decay, demonstrating a significant potential in practical application.