In-situ sulfuration synthesis of N,S-doped carbon nanosheet encapsulated Fe-doped Co9S8 as anodes for tunable lithium storage

Abstract Transition-metal sulfides (TMSs), in particular Co 9 S 8 , have been investigated intensively owing to their unique properties and various applications, especially such as lithium-ion batteries (LIBs). Co 9 S 8 nanostructures as anode nanomaterials for LIBs are synthesized typically by using different sulfuration approaches with the necessity of additionally introducing conventional sulfur sources (such as sulfur power or thiourea), and their electrochemical performances are enhanced by hybridizing pristine Co 9 S 8 with other active TMSs and carbonaceous support. Herein, the in-situ sulfuration preparation of Fe-doped (Fe 0.25 Co 0.75 ) 9 S 8 nanoparticle embedded within N,S-doped amorphous carbon as anode nanomaterials for LIBs is demonstrated via a solid-solid sulfuration reaction during the pyrolysis of mixture of a scalablely produced ternary Co 2+ Fe 3+ Al 3+ -layered double hydroxide (Co 2+ Fe 3+ Al 3+ -LDH) and an easily available N,S-containing dye (acid yellow 49) serving as both sulfur and carbon sources. The in-situ sulfuration preparation, without the additional introduction of traditional sulfur source, endows the composite with the following features: bi-metallic (Fe 0.25 Co 0.75 ) 9 S 8 and N,S-doped amorphous carbon encapsulation. The composite electrode indeed delivers a decent rate capability, and, in particular, a long-term cycling stability of 408 mA h g −1 after the 300 cycles at 500 mA g −1 . Furthermore, a similar (Fe 0.28 Co 0.72 ) 9 S 8 /N,S-C composite with boosted electrochemical performances is prepared via choosing a different Mg 2+ Co 2+ Fe 3+ –LDH/AY49 precursor using the same LDH precursor-based in-situ sulfuration procedure. Given the unique flexibility in tuning cation type and molar ratio of LDH precursors, our results provide an eco-efficient synthesis route for designing and preparing diverse transition-metal sulfides and even phosphides for energy storage.