Enhanced catalytic activity and stability in lithium-sulfur batteries using Ti3C2Tx/NbSe2 heterostructured electrocatalysts

Lithium-sulfur (Li-S) batteries hold promise as high-energy storage systems; however, their practical application is hindered by challenges such as the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics. In this study, we designed and synthesized Ti3C2Tx/NbSe2 electrocatalyst through in-situ hydrothermal growth and selenization steps. NbCl5 was selenized to form Ti3C2Tx/NbSe2, which was evaluated as a cathode material. The resulting Ti3C2Tx/NbSe2 material was precisely characterized by FESEM, TEM, XRD and XPS analyses. The Ti3C2Tx/NbSe2 exhibited a high BET specific surface area of 89.16 m2 g- 1 and a pore volume of 0.098 cm3 g- 1, indicating enhanced adsorption capabilities for LiPSs. Electrochemical performance tests demonstrated the superior catalytic activity and redox kinetics of Ti3C2Tx/NbSe2 compared to those of pure Ti3C2Tx and NbSe2. Cyclic voltammetry (CV) profiles indicated higher current densities, and Tafel plots revealed an increased exchange current density of 1.19 mA cm- 2 for the Ti3C2Tx/NbSe2. Li2S precipitation experiments showed an enhanced precipitation current density of 416.8 mA g- 1 and a higher capacity of 198.6 mAh g- 1 for the Ti3C2Tx/ NbSe2. The S/Ti3C2Tx/NbSe2 cathode exhibited outstanding rate capabilities, with capacities of 1389-716 mAh g- 1 at current densities of 0.1-5 C, respectively. Moreover, it maintained a high discharge capacity of 954 mAh g- 1 when the current density returned to 0.5 C. The long-term cycling stability was demonstrated with a capacity retention of 94.8 % over 550 cycles at 0.5 C, significantly outperforming the S/Ti3C2Tx and S/NbSe2 cathodes. Additionally, under a high sulfur loading of 6.5 mg cm-2 at 0.2 C, the S/Ti3C2Tx/NbSe2 cathode exhibited an initial area capacity of 6.13 mAh cm- 2, retaining a capacity of 3.45 mAh cm- 2 after 300 cycles.