Enhanced pseudocapacitance contribution to outstanding Li-storage performance for a reduced graphene oxide-wrapped FeS composite anode

Abstract

To meet heavy-duty applications for LIBs, development of superior electrode materials with high-efficiency lithium-storage capability has become very crucial and urgent. Herein, a simple one-pot method has been developed for the synthesis of a reduced graphene oxide-wrapped FeS nanoflake (FeS@rGO) composite using oleylamine as a solvent, reductant, and surfactant. The as-prepared FeS@rGO composite as an anode material for LIBs showed excellent cycling ability and rate performance, i.e., reversible capacities of 887 mA h g⁻¹ at the current density of 200 mA g⁻¹ after 150 cycles, 662 mA h g⁻¹ at 1.0 A g⁻¹ after 200 cycles, and 325 mA h g⁻¹ at 5.0 A g⁻¹ even after 1000 cycles. These enhanced electrochemical performances can be attributed to the unique cladding structure, in which rGO can act as a protective coating to accommodate volume changes of FeS upon Li-cycling and offer a fast electron transfer channel. A two-dimensional sheet structure also facilitates Li⁺ ion diffusion in active electrode materials. More importantly, the enhanced extrinsic pseudocapacitance can promote the charge transfer rate and afford significant Li-storage capacity, thereby promoting the rate capability of a material at large current densities. Therefore, as a promising anode with high power density and long lifespan, this composite has shown its distinct potential and advantage for heavy-duty LIBs.