Spatially Confined Fe7S8 Nanoparticles Anchored on a Porous Nitrogen-Doped Carbon Nanosheet Skeleton for High-Rate and Durable Sodium Storage

Iron sulfides are widely explored as anodes of sodium-ionbatteries(SIBs) owing to high theoretical capacities and low cost, but theirpractical application is still impeded by poor rate capability andfast capacity decay. Herein, for the first time, we construct highlydispersed Fe7S8 nanoparticles anchored on aporous N-doped carbon nanosheet (CN) skeleton (denoted as Fe7S8/NC) with high conductivity and numerous active sites via facile ion adsorption and thermal evaporation combinedprocedures coupled with a gas sulfurization treatment. Nanoscale designcoupled with a conductive carbon skeleton can simultaneously mitigatethe above obstacles to obtain enhanced structural stability and fasterelectrode reaction kinetics. With the aid of density functional theory(DFT) calculations, the synergistic interaction between CNs and Fe7S8 can not only ensure enhanced Na+ adsorptionability but also promote the charge transfer kinetics of the Fe7S8/NC electrode. Accordingly, the designed Fe7S8/NC electrode exhibits remarkable electrochemicalperformance with superior high-rate capability (451.4 mAh g(-1) at 6 A g(-1)) and excellent long-term cycling stability(508.5 mAh g(-1) over 1000 cycles at 4 A g(-1)) due to effectively alleviated volumetric variation, acceleratedcharge transfer kinetics, and strengthened structural integrity. Ourwork provides a feasible and effective design strategy toward thelow-cost and scalable production of high-performance metal sulfideanode materials for SIBs.

Automated summary

Iron sulfide nanoparticles dispersed on a porous N-doped carbon nanosheet were successfully synthesized and demonstrated improved stability and capacity in sodium-ion batteries. The design strategy involving nanoscale design and conductive carbon skeleton provided enhanced structural stability and faster electrode reaction kinetics. The Fe7S8/NC electrode exhibited outstanding high-rate capability (451.4 mAh g(-1) at 6 A g(-1)) and excellent long-term cycling stability (508.5 mAh g(-1) over 1000 cycles at 4 A g(-1)) due to alleviated volumetric variation, accelerated charge transfer kinetics, and strengthened structural integrity.