A Ternary Fe _{1− x} S@Porous Carbon Nanowires/Reduced Graphene Oxide Hybrid Film Electrode with Superior Volumetric and Gravimetric Capacities for Flexible Sodium Ion Batteries

Smart construction of ultraflexible electrodes with superior gravimetric and volumetric capacities is still challenging yet significant for sodium ion batteries (SIBs) toward wearable electronic devices. Herein, a hybrid film made of hierarchical Fe ₁₋ _x S-filled porous carbon nanowires/reduced graphene oxide (Fe ₁₋ _x S@PCNWs/rGO) is synthesized through a facile assembly and sulfuration strategy. The resultant hybrid paper exhibits high flexibility and structural stability. The multidimensional paper architecture possesses several advantages, including rendering an efficient electron/ion transport network, buffering the volume expansion of Fe ₁₋ _x S nanoparticles, mitigating the dissolution of polysulfides, and enabling superior kinetics toward efficient sodium storage. When evaluated as a self-supporting anode for SIBs, the Fe ₁₋ _x S@PCNWs/rGO paper electrode exhibits remarkable reversible capacities of 573–89 mAh g ⁻¹ over 100 consecutive cycles at 0.1 A g ⁻¹ with areal mass loadings of 0.9–11.2 mg cm ⁻² and high volumetric capacities of 424–180 mAh cm ⁻³ in the current density range of 0.2–5 A g ⁻¹ . More competitively, a SIB based on this flexible Fe ₁₋ _x S@PCNWs/rGO anode demonstrates outstanding electrochemical properties, thus highlighting its enormous potential in versatile flexible and wearable applications. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim