Poly(ionic liquid) derived N-doped carbon@SnO_x nanostructures self-reconstruction for alkaline-metal-ion batteries

High performance of lithium- and sodium-ion batteries requires their electrodes with rationally designed morphology and chemical composition. This work reports a facile synthesis of SnO_x coated by nitrogen-doped carbon (N–C@SnO_x, x = 0, 2) employing an imidazolium-type poly(ionic liquid) bearing Tf₂N⁻ as a sole carbon and nitrogen precursor. SnO₂ nanospheres are first prepared via hydrothermal method and then decorated by a thin PIL coating by electrostatic interaction. Under subsequent carbonization, PIL is carbonized to nitrogen doped carbon which spontaneously reduces SnO₂ partially to produce N–C@SnO_x. Such N–C@SnO_x delivers a high capacity of 691 mAh g⁻¹ over 650 cycles at 1 A g⁻¹ for lithium-ion batteries, and shows a satisfactory capacity of 336 mAh g⁻¹ over 100 cycles at 0.1 A g⁻¹ for sodium-ion batteries.