Graphene encapsulated iron nitrides confined in 3D carbon nanosheet frameworks for high-rate lithium ion batteries

Abstract

Metal nitrides with high theoretical capacities and exceptional electrical conductivities hold great potentials as high-rate anode materials for lithium ion batteries (LIBs), but suffer from severe pulverization and air instability of electrodes. Herein, we developed a general strategy for synthesizing few-layer graphene encapsulated transition metal nitride (e.g., Fe2N) nanoparticles confined in three dimensional (3D) ultrathin carbon nanosheet frameworks (denoted as Fe2N@CNFs) via the iron nitrate accelerated polyvinylpyrrolidone (PVP) blowing and subsequent in-situ nitridation process, as high-rate anode for LIBs. Benefiting from the well-confined Fe2N nanoparticles by graphene shells for alleviating structural pulverization and air sensitivity, and 3D carbon nanosheet porous frameworks for fast electrolyte ion diffusion and fast electron transport, the resulting Fe2N@CNFs anodes exhibited high reversible capacity of 587 mA h g−1 at 0.1 A g−1, and remarkable rate capacity of 215 mA h g−1 at high current density of 10 A g−1, outperforming most reported metal nitride electrodes. When coupled with carbon-coated LiFePO4 cathode, the resulting full LIBs still delivered an initial discharge capacity of 243 mA h g−1 at 0.1 A g−1. Therefore, this work will pave a new way for rational construction of a series of high-performance metal nitride electrodes for energy-related devices.