Defect-Rich Multishelled Fe-Doped Co₃O₄ Hollow Microspheres with Multiple Spatial Confinements to Facilitate Catalytic Conversion of Polysulfides for High-Performance Li–S Batteries

Abstract

Over the past decade, lithium-sulfur (Li-S) batteries have been thought of as promising alternatives for the new generation of battery systems. Although the Li-S batteries possess high-theoretical energy density (2600 Wh kg^-1) and capacity (1675 mAh g^-1), the problems of poor electron and ion conduction, volumetric expansion, and sulfur immobilization greatly impede the wide applicability of Li-S batteries. Herein, a defect-rich multishelled Co₃O₄ microsphere structure doped with Fe was synthesized via a one-step hydrothermal method and subsequent thermal treatment. The unique multishelled structure provides multiple spatial confinements for lithium polysulfides trapping and buffering the volume variation during cycling. Moreover, the rich oxygen defect designed by controlled Fe doping can provide numerous catalytic sites for polysulfide redox reactions. Attributed to the synergistic effect of structural design and oxygen-defect fabrication, the sulfur composite electrode delivers a notable cycle performance, presenting a much lower capacity fading of 0.017% per cycle over 1000 cycles at 1 C and an excellent rate capability of 571.3 mAh g^-1 at 5 C. This work proposes a potential approach for designing a transition metal oxide-based multishelled hollow structure combined with oxygen defect, which also offers a new perspective on high-performance Li-S batteries.