Resorcinol Formaldehyde Resin-Coated Prussian Blue Core Shell Spheres and Their Derived Unique Yolk Shell FeS2@C Spheres for Lithium-Ion Batteries

The practical applications of transition metal sulfides as electrode materials for lithium-ion batteries (LIBs) is greatly hindered by the fast capacity fading owing to the large volume expansion. To address this issue, construction of transition metal sulfide and carbon nanocomposites with unique yolk shell structures is an effective strategy but also remains a great challenge. In this work, we reported a facile approach to synthesize the unique yolk-shell FeS2@carbon (FeS2@C) spheres via calcination treatment of the resorcinol-formaldehyde (RF) resin-coated Prussian blue (FeFe PB) core-shell spheres in Ar atmosphere and a subsequent sulfidation treatment. The synthetic method herein was quite simple and convenient. Such unique structure design could effectively prevent the large volume expansion and dissolution of the active materials in the electrolytes during lithiation. As expected, the yolk-shell FeS2@C spheres exhibited good electrochemical performance as anode materials for LIBs, which displayed a high discharge capacity of 560 mA h g(-1) at 100 mA g(-1) for 100 cycles. When the current density increased to 1000 mA g(-1), a reversible discharge capacity of 269 mA h g(-1) was still retained after 500 cycles. The present work demonstrated an extraordinary synthetic strategy to construct transition metal sulfide and carbon nanocomposites with unique yolk shell structure. In addition, this RF resin coating strategy can be further extended to synthesize other RF resin-coated PB analogue (PBA) core -shell nanostructures, demonstrating the generality of this RF resin coating strategy.