1T-VSe 2 @Ti 3 C 2 Heterostructure with a Built-In Electric Field and Li x VSe 2 Intercalation–Conversion for High-Performance Li–S Chemistry: Accelerating Sulfur Conversion and Lithium-Ion Transport

Lithium–sulfur (Li–S) batteries are considered a promising alternative to conventional lithium-ion batteries due to their high theoretical capacity. However, the lithium polysulfide shuttle effect and inefficient redox kinetics impede their practical application. In this study, a 1T-VSe 2 @Ti 3 C 2 heterostructure was rationally designed via a facile one-step hydrothermal method. The heterostructure, composed of conductive MXene and metallic 1T-VSe 2, forms a built-in electric field that effectively promotes electron transport, which is beneficial for enhancing polysulfide adsorption and boosting sulfur conversion kinetics. Furthermore, a dynamic intercalation–conversion site (Li x VSe 2 ) improved lithium-ion transport and redox reversibility, which is confirmed by XPS analysis and in situ Raman spectroscopy. Therefore, Li–S cells with 1T-VSe 2 @Ti 3 C 2 -modified separators exhibited exceptional electrochemical performance, achieving an initial capacity of 1457 mAh g – 1 with a high retention rate of 71%, a high-rate capability of 847 mAh g – 1 at 4 C, and a durable cycle life with a capacity attenuation rate of 0.06% per cycle at 1 C over 1000 cycles. Notably, a reversible areal capacity of 4.8 mAh cm – 2 is maintained under a high sulfur loading (5.5 mg cm – 2 ) after 100 cycles at 0.2 C. This work provides a universal strategy for constructing separator modifiers based on transition-metal selenides and highlights the potential of heterostructure engineering for achieving durable and practical Li–S batteries.