Fe7Se8@C core–shell nanoparticles encapsulated within a three-dimensional graphene composite as a high-performance flexible anode for lithium-ion batteries

Abstract

Nanocomposites with tailored core–shell structure encapsulated within three-dimensional graphene (3DG) architectures are attractive for applications of electrochemical energy storage. Here, we design a hierarchical structure with nanoparticles consisting of the Fe₇Se₈-enriched inner core and the carbon-enriched outer shell encapsulated within three-dimensional graphene (denoted as 3DG/Fe₇Se₈@C) by using a 3DG/metal organic framework (MOF) aerogel as the template to react with Se powder at elevated temperatures. This unique structure provides an excellent conductive and mechanically robust network which benefits electronic transport and suppresses volume change effectively. When directly used as a flexible anode for lithium-ion batteries, the 3DG/Fe₇Se₈@C composite exhibited a high reversible capacity of 884.1 mA h g⁻¹ at 0.1 A g⁻¹ after 120 cycles and 815.2 mA h g⁻¹ at 1 A g⁻¹ after 250 cycles between 0.01 and 3.00 V, as well as an exceptional rate performance.