Bifunctional electrocatalytic hybrid heterostructures for polysulfide anchoring/conversion for a stable lithium–sulfur battery†

In situ phase engineering of transition metal dichalcogenides (TMDs) with controlled sulfur vacancies offers a promising strategy for superior-performance lithium–sulfur (Li–S) batteries. Herein, we demonstrate a bifunctional approach by designing a sulfur host material using 1T-MoS₂/MoO₃ heterostructures grown directly on carbon nanopot-resembling designer structures (CMS). The metallic phase (1T-MoS₂) with MoO₃ synergistically contributes to exceptional electronic transport, increased interlayer spacing, and more electrochemically active sites across its basal plane. Carbon nanopot structures and sulfur vacancies within the TMDs act as anchoring sites for lithium polysulfides (LiPSs). Additionally, the specifically phase-engineered 2D heterostructure promotes their efficient conversion into the electrochemically favorable Li₂S phase. This dual functionality is expected to significantly improve the rate capability and cycle life stability of Li–S batteries. This translates to a high reversible rate capacity of 1205 mA h g⁻¹ at a current density of 0.2 A g⁻¹. The sulfur-loaded CMS nanostructure shows an excellent cycling life with a decay rate of only 0.078% over 1100 cycles at 1 A g⁻¹, underscoring the effectiveness of the in situ phase engineering approach for creating a stable Li–S battery.