Facile Synthesizing Yolk-Shelled Fe₃O₄@Carbon Nanocavities with Balanced Physiochemical Synergism as Efficient Hosts for High-Performance Lithium–Sulfur Batteries

The severe “shuttle effect” of dissolved polysulfide intermediates and the poor electronic conductivity of sulfur cathodes cause capacity decay of lithium–sulfur batteries and impede their commercialization. Herein, we synthesized a series of well-designed yolk-shelled Fe₃O₄@carbon (YS-Fe₃O₄@C) nanocavities with different proportions of Fe₃O₄ as efficient sulfur hosts to stabilize polysulfide intermediates. The yolk-shelled nanocavity architectures were prepared through a facile method, which could effectively confine the active materials and achieve high conductivity. The polysulfide intermediate shuttle was successfully suppressed by a physiochemical synergism effect combining the retention of carbon shells and the adsorption of Fe₃O₄ nanoparticle cores. The highly conductive carbon shell provides efficient pathways for fast electron transportation. Meanwhile, the visible evolution of active materials and a reversible electrochemical reaction are revealed by in situ X-ray diffraction. With the balanced merits of enhanced electrical conductivity of carbon shell and optimal adsorption of Fe₃O₄ cores, the S/YS-27Fe₃O₄@C cathode (Fe₃O₄ accounts for 27 wt% in YS-Fe₃O₄@C) had the best electrochemical performance, exhibiting a high reversible specific capacity of 731.9 mAh g⁻¹ and long cycle performance at 1 C (capacity fading rate of 0.03% over 200 cycles).