Carbon nanofiber linked FeS2 mesoporous nano-alloys as high capacity anodes for lithium-ion batteries and supercapacitors

Highlights: • One pot microwave synthesis of carbon nano fiber linked FeS₂ nano-platelet ensembles is developed. • The lithium ion capacity of FeS₂-CNF nano-alloys was significantly improved. • FeS₂-CNF nano-alloys show excellent performance in super-capacitors. Iron sulfide, commonly known as fool's gold, is rapidly emerging as an attractive material for both energy conversion (in photovoltaics) and energy storage, especially as an electrode in lithium-ion batteries. In this manuscript, we report on a simple one-pot two-step technique for synthesis of carbon nanofiber (CNF) cross-linked FeS₂ networks, by microwave pyrolysis of ferrocene to iron decorated CNF and its subsequent sulfidation by a sustainable source, namely, l-cysteine. When used as the negative electrode in lithium-ion batteries, our 3D mesoporous FeS₂–CNF hybrids exhibit high capacity of 994 mAhg⁻¹ even after 300 cycles, which exceeds the theoretical capacity of FeS₂ (894 mAhg⁻¹). Additionally, when applied as super-capacitor electrodes, our microwave-synthesized FeS₂–CNF electrodes exhibit high capacitance of 612 and 342 Fg^-1 at 5 and 100 mVs⁻¹, respectively, and long-term cyclability, with 97% capacitance retention after 2000 cycles.