Multi-Interface Engineering Modulated Bidirectional Polysulfide Conversion for Advanced Lithium-Sulfur Batteries
Lithium-sulfur batteries (LSBs) are recognized as a leading candidate for next-generation energy storage due to their high theoretical specific capacity (1675 mAh g⁻¹). However, the shuttle effect of lithium polysulfides (LiPSs) severely limits cycle life and energy efficiency. Here, we report a multi-interface engineering strategy employing a MnO₂-TiO₂@Ti₃C₂ MXene (MT@MX) heterojunction, synthesized via a facile redox reaction between MXene and KMnO₄, to modulate bidirectional polysulfide conversion. The 2D structure with high conductivity and abundant heterogeneous interfaces facilitates fast ion/electron transfer, reduces reaction energy barriers, and enhances adsorption via d-band center effects. The stepped built-in electric field (BIEF) in MT@MX lowers the migration energy barrier of LiPSs from catalytic MXene to TiO₂ and then to adsorptive MnO₂, enabling reversible migration across multi-interfaces. Optimized heterointerfaces synergistically integrate adsorption, diffusion, and catalytic conversion, yielding excellent cycling stability even at a high sulfur loading of 6.4 mg cm⁻². This work demonstrates that constructing heterojunctions with stepped BIEF offers a feasible approach to modulate interfacial diffusion and provides a new design strategy for high-performance LSB electrocatalysts.