Hierarchical iron selenide nanoarchitecture as an advanced anode material for high-performance energy storage devices

Herein, we report submicron-sized flower-like iron selenide (FeSe2, FS) nanostructure facilely prepared using a KCl-templated solvothermal technique followed by calcination treatment under an inert atmosphere. As an anode material in lithium ion batteries (LIBs), the as-prepared flower-like FS nanostructure exhibits a specific discharge/charge capacity of 701/694 mAh g−1 with good faradaic efficiency of 99% after 100 cycles. Even at a high current density of 3200 mA g−1, the flower-like FS nanostructure material displays an outstanding reversible specific capacity of 435 mAh g−1 after 500 charge-discharge cycles. The rate capability performance also shows the excellent structural stability of the as-prepared electrode material, which could be due to the hollow cavity and free space in the flower-like FS nanostructure that can accommodate a larger number of Li ions and active sites for higher density energy storage. Furthermore, we demonstrate the use of the as-prepared flower-like FS nanostructure as negative electrodes for supercapacitors in aqueous alkaline electrolyte. In this application, they exhibit a maximum specific capacitance of 362.1 F g−1 along with good cycling durability of 89.4% after 5000 charge-discharge cycles. The facile preparation of hierarchical iron-based selenide that possess superior energy storage properties could be useful for the preparation of other metal selenide-based anode materials for use in high-performance energy storage devices.