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

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.

Automated summary

The hollow CoxFe3-xO4 heterostructure nanocages obtained through a PBA-assisted strategy can effectively overcome the issues in lithium-sulfur batteries, significantly improving their performance and cycling stability.