Poly(ionic liquid)-derived nitrogen-doped hollow carbon spheres: synthesis and loading with Fe2O3 for high-performance lithium ion batteries

Porous nitrogen-doped hollow carbon spheres (NHCSs) with tailored particle size, nitrogen content and wall thickness were prepared by grafting a thin layer of poly(ionic liquid) as carbon precursor onto silica particle surface followed by carbonization and template removal. In the next step, Fe2O3 nanoparticles were anchored onto the NHCSs via an impregnation-thermal decomposition route using Fe(NO3)3 as iron source. The as-synthesized Fe2O3–NHCS composite was utilized as the anode material for a lithium-ion battery, which exhibited a high reversible capacity of 1120 mAh g−1 at a rate of 100 mA g−1, and a coulombic efficiency of ∼98% at a rate of 500 mA g−1 after 65 cycles.