Enhancing Catalytic Conversion of Polysulfides by Hollow Bimetallic Oxide-Based Heterostructure Nanocages for Lithium-Sulfur Batteries

Abstract

Performance improvement of lithium-sulfur batteries (LSBs) is restricted by the dissolution and shuttle of lithium polysulfides (LiPSs). Prussian blue analogs (PBAs) and their derived nanomaterials are ideal sulfur-fixing materials owing to their abilities to anchor LiPSs, accelerate redox conversion, and smooth Li2S precipitation. Herein, the hollow CoxFe3–xO4 heterostructure nanocages with highly interconnected pore architecture obtained by a PBA-assisted strategy are synthesized to overcome the abovementioned obstructions of LSBs. It is found that the bimetallic oxide-based heterostructure can not only inhibit LiPS diffusion via forming metal–sulfur bonds but also accelerate the LiPS conversion kinetics. Meanwhile, the hollow porous structure contributes to the physical confinement of LiPSs and acts as a buffer for the volume change. Thereby, the rate capability and cycling stability of hollow CoxFe3–xO4@S composite electrodes have been improved significantly. As a result, the hollow CoxFe3–xO4@S cell displays an excellent initial capacity of 1301.6 mAh g–1 at a current density of 200 mA g–1. Even at 1 A g–1, it exhibits an outstanding initial capacity of 898.9 mAh g–1 with a negligible capacity loss rate, which is only 0.106% per cycle after 500 cycles. This work provides a new perspective for the construction and design of multifunctional hollow heterostructure materials for more efficient and stable LSBs.