Constructing FeS2/TiO2 p-n heterostructure encapsulated in one-dimensional carbon nanofibers for achieving highly stable sodium-ion battery

Iron sulfides (FeS2) is a promising anode material for advanced sodium-ion batteries (SIBs) owing to its high theoretical capacity of 894.0 mAh/g and abundant natural resource. However, the inferior electronic conductivity, huge volume expansion, and dissolution of sodium polysulfides generated upon conversion reaction process limit its practical application in SIBs. Although the introduction of carbon materials could significantly compensate for conductivity and structural destroy, but the poor cycling stability aroused by active sulfide loss still urgently settled. Herein, TiO2 featuring strong affinity for sodium polysulfides was engaged as one active component to construct FeS2/TiO2 heterostructure. Additionally, TiO2 is a typical n-type semiconductor with a broad bandgap, which will induce the formation of a strong built-in electric field at the interface of FeS2/TiO2 and thus expedite the charge transport during sodium storage process. Consequently, FeS2/TiO2 p-n heterostructure nanoparticles encapsulated in one dimensional carbon nanofibers (FeS2/TiO2@CNFs) were synthesized by simple electrospinning technology and subsequent carbonization/sulfidation treatment, as well as systemically investigated its electrochemical performance as an anode material for SIBs. As expected, FeS2/TiO2@CNFs anode delivers a high specific capacity of 563.1 mAh g-1 at 1.0 A g-1 over 100 cycles, and superior rate capability (404.0 mAh g-1 at 10.0 A g-1). Even after 8000 cycles at 10.0 A g-1, FeS2/TiO2@CNFs anode still exhibits superior cycling durability. Inspired by the admirable sodium storage performance of FeS2/TiO2@CNFs heterostructure, the architectural design strategy is expected to be widely adopted for meliorating the electrochemical performance of metal sulfide anodes.