Mesoporous C-coated SnOx nanosheets on copper foil as flexible and binder-free anodes for superior sodium-ion batteries

Abstract

Carbon-coated binder-free flexible porous SnO_x nanosheets (SnO/SnO₂ heterogeneous structure) were fabricated and tested as anode materials for Na-ion batteries (NIBs). The novel free-standing and binder-free porous C@SnO_x nanosheets were first self-assembled on a Cu substrate via a facile, low-cost anodization method followed by the carbonization treatment. Instrumental analyses show that the porous C@SnO_x nanosheets exhibit a remarkably large surface area of 221 m² g⁻¹, delivering a reversible discharge capacity of 510 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹, demonstrating great potential for Na⁺ storage applications. The superior electrochemical performance is ascribed to the unique hierarchical porous architecture which greatly facilitates electrolyte penetration and ion transportation with the carbon coating further increasing the electrode conductivity and alleviating strains generated by volume change upon Na⁺ ion insertion/extraction.