Metal-Organic-Framework-Derived FeSe2@Carbon Embedded into Nitrogen-Doped Graphene Sheets with Binary Conductive Networks for Rechargeable Batteries

Metal selenides have been widely studied as anodes for lithium-ion batteries, owing to the excellent electrochemical performance. However, the large volume change and poor conductivity may lead to unsatisfactory cycling stability and rate capability. Herein, the FeSe2/carbon matrix nanoparticles embedded into N-doped graphene sheets (NGS) are designed and synthesized through a two-step method. When employed as anodes for lithium-ion batteries, the FeSe2/C@NGS composites exhibit high reversible specific capacities and excellent cycling stabilities of 757.0mAhg(-1) after 100 cycles at 100mAg(-1) and 593.8mAhg(-1) after 1000 cycles at 2000mAg(-1). The carbon matrix and NGS construct binary conductive networks, which not only improve the inner conductivity of FeSe2 and conductivity between FeSe2/C nanoparticles, but also provide elastic buffer space to sustain the structural strain and accommodate the volume expansion and contraction of electrodes during the discharge and charge process. Furthermore, the reversible redox reaction of FeSe2 involves the formation of Fe and Li2Se during the cycling process. This work may open a new avenue for electrode material synthesis methodologies using metal-organic frameworks as a template and to explore the lithium storage mechanisms of metal selenides for next-generation batteries.