# Facilitated Polysulfide Redox Conversion by Delocalized Electrons in MBene Heterointerface for Highly Stable Lithium–Sulfur Batteries

## TL;DR

A new 2D material structure improves lithium-sulfur battery performance by reducing energy loss and increasing stability.

## Contribution

A fluorine-free method creates a WB@WC heterostructure that enhances electron delocalization and LiPSs redox conversion.

## Key findings

- The WB@WC heterostructure achieved an area capacity of 7.9 mAh cm−2 with minimal capacity decay (~0.024% per cycle).
- In situ X-ray absorption spectroscopy confirmed the catalytic mechanism of WB-based MBene during LiPSs redox cycles.
- The material effectively suppresses the shuttle effect and improves reaction kinetics for Li–S batteries.

## Abstract

A multifunctional 2D tungsten boride (WB)@tungsten carbide (WC) heterostructure was innovatively fabricated by a fluorine-free MBene etching process and in situ carbonization technology.The enhanced local electron delocalization effect at the heterointerface effectively suppressed the shuttle effect and improved the reaction kinetics, achieving an area capacity of up to 7.9 mAh cm−2 and a capacity attenuation as low as ~ 0.024% per cycle.In situ X-ray absorption spectroscopy verified the catalytic mechanism of WB-based MBene.

A multifunctional 2D tungsten boride (WB)@tungsten carbide (WC) heterostructure was innovatively fabricated by a fluorine-free MBene etching process and in situ carbonization technology.

The enhanced local electron delocalization effect at the heterointerface effectively suppressed the shuttle effect and improved the reaction kinetics, achieving an area capacity of up to 7.9 mAh cm−2 and a capacity attenuation as low as ~ 0.024% per cycle.

In situ X-ray absorption spectroscopy verified the catalytic mechanism of WB-based MBene.

The online version contains supplementary material available at 10.1007/s40820-026-02100-3.

The shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics severely restrict the development of high-energy lithium–sulfur (Li–S) batteries. To alleviate this issue, this study adopts an in situ design strategy to construct tungsten carbide (WC) nanocrystals on the surface of two-dimensional (2D) tungsten boride (WB)-based MBene, creatively forming a WB@WC heterostructure to optimize the adsorption–migration–catalysis mechanism of LiPSs. The WB–WC heterointerface reduces the reaction energy barrier of LiPSs due to the electron delocalization effect and promotes the deposition/dissociation of Li2S and the transfer of charge. In situ Raman verified that WB@WC can effectively inhibit LiPSs shuttling. In situ X-ray absorption fine structure spectroscopy (XAFS) characterizations further explored the dynamic change of W valence state during LiPSs redox cycle. Encouragingly, the WB@WC-modified Li–S cell delivers an initial capacity of 1277 mAh g−1 at 0.2 C. It exhibits extremely stable cycling performance at 2 C, with a low-capacity decay rate of only ~ 0.024% per cycle. Even under sulfur loading of 7.92 mg cm−2, high capacity of 7.9 mAh cm−2 can still be achieved. This work provides an effective method for regulating the activity of MBene-based catalysts.

The online version contains supplementary material available at 10.1007/s40820-026-02100-3.