N-doped hard carbon ultrathin film-coated Fe1−xS nanoparticles with multi-morphologies for cheap Li ion battery anodes

The lithium storage performance and bioimaging of metal sulfides are restricted by their intrinsic poor conductivity, large volumetric expansion and toxicity. Here we report a new strategy to solve these problems by coating pyrrhotite (Fe1−xS) (FS) nanoparticles with N-doped hard carbon ultrathin film (N-HCUF). The porous nanocomposites with multilevel structures have been synthesized by using petrochemical waste water (PWW) as the organic ligands of iron metal–organic frameworks (Fe-MOFs) precursor and the sources of sulfur, nitrogen and carbon. We have clarified the formation mechanism and the influences of wash and calcination temperature on the structural composition, electrochemical and luminescence properties of the nanocomposites. As a novel anode for lithium ion batteries (LIBs), the FS/N-HCUF-700S exhibits high initial discharge capacity of 1542.08 mAh g−1 at a current density of 0.1 A g−1 and the discharge specific capacity becomes stable at 632.16 mAh g−1 after 200 cycles; Meanwhile, the Li+ storage mechanism in the as-prepared samples has also been investigated. More importantly, FS/N-HCUF-700S exhibits strong yellow-fluorescent emission at 614 nm, which is particularly important for bioimaging. Last, the removal efficiency of chemical oxygen demand of PWW is up to 80.7% during the synthesis process.