Facile fabrication of a jarosite ultrathin KFe3(SO4)2(OH)6@rGO nanosheet hybrid composite with pseudocapacitive contribution as a robust anode for lithium-ion batteries

The search for anode materials with high performance and low cost for lithium-ion batteries (LIBs) remains challenging. Herein, Earth-abundant and acid-resistant jarosite ultrathin KFe3(SO4)2(OH)6@rGO (KFN@rGO) nanosheets were fabricated via a facile and scalable hydrothermal route without any surfactant. When serving as an anode material for LIBs, KFN@rGO delivers excellent lithium storage performances, including high reversible capacity (913 mA h g−1 at 20 mA g−1) and robust cycling life (545 mA h g−1 at the end of 1000 cycles at 500 mA g−1). Moreover, the pseudocapacitive contribution is as high as 62.7% at 1 mV s−1 as revealed by cyclic voltammetry. The robust cycling stability can be attributed to the hybrid structure of ultrathin KFe3(SO4)2(OH)6 nanosheets and flexible rGO which not only enhances the conductivity and structural integrity, but also induces the pseudocapacitive effect during the cycles. This work may provide an effective route to improve the electrochemical performances of other jarosite minerals through the introduction of the pseudocapacitive contribution.