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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 Fe₁₋ₓS-filled porous carbon nanowires/reduced graphene oxide (Fe₁₋ₓS@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 Fe₁₋ₓS nanoparticles, mitigating the dissolution of polysulfides, and enabling superior kinetics toward efficient sodium storage. When evaluated as a self-supporting anode for SIBs, the Fe₁₋ₓS@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 Fe₁₋ₓS@PCNWs/rGO anode demonstrates outstanding electrochemical properties, thus highlighting its enormous potential in versatile flexible and wearable applications.

Metal sulfides with excellent redox reversibility and high capacity are very promising electrode materials for sodium-ion batteries. However, their practical application is still hindered by the poor rate capability and limited cycle life. Herein, a template-based strategy is developed to synthesize nitrogen-doped carbon-coated Cu₉S₅ bullet-like hollow particles starting from bullet-like ZnO particles. With the structural and compositional advantages, these unique nitrogen-doped carbon-coated Cu₉S₅ bullet-like hollow particles manifest excellent sodium storage properties with superior rate capability and ultra-stable cycling performance. Ministry of Education (MOE) X.W.L. acknowledges the funding support from the Ministry of Education of Singapore through AcRF Tier-1 funding (RG5/17(S), M4011783.120).