Adapting FeS2 micron particles as an electrode material for lithium-ion batteries via simultaneous construction of CNT internal networks and external cages

Abstract

Volume changes, polysulfide shuttle effects, and low Li-ion/electronic conductivity of sulfide electrodes limit their application in Li-ion batteries with high-energy density. Here, micron FeS₂ particles with bifunctional carbon nanotubes (FeS₂@B–CNTs) including CNT internal conductive networks and external protective cages were prepared by a one-step solvothermal method. The internal CNTs anchor FeS₂via chemical binding, which much more effectively inhibited the shuttle effect than physical confinement alone. Meanwhile, reticular CNT cages were generated on the surface of the composite FeS₂ micron particles, buffering volumetric changes during cycling and further restraining the shuttle of polysulfides. Additionally, a three-dimensional CNT framework offered a primarily continuous charge transfer pathway. The FeS₂@B–CNTs electrode had a high initial coulombic efficiency of 91.3% and delivered a capacity of 698 mA h g⁻¹ over 500 cycles at 1000 mA g⁻¹. The Li-ion diffusion coefficient is two orders of magnitude higher than those of previous reports, which improved the rate performance of the FeS₂@B–CNTs electrode. These studies on micron FeS₂ spheres shed light on the design strategies for the application of sulfide electrodes.