Synergistically Engineered Sulfur-Infiltrated Carbon Nanotube–Titanium Nitride–Tungsten Trioxide Heterostructure Cathodes for Unlocking Superior Potential of Lithium–Sulfur Batteries

Abstract The rational design of heterostructure cathode materials with suitable separators is critical for mitigating polysulfide shuttling in lithium–sulfur batteries (LiSBs). In order to achieve high Li+-kinetics, the design of the cathode material plays a vital role in the sluggish polysulfides (PS) shuttle conversion. In this study, CNT–TiN heterostructures were synthesized via the chemical vapor deposition method along with varying wt % of WO3 (10%, 25%, and 50%), which was hybridized with sulfurization to acquire ‘S’ infiltrated CNT–TiN–WO3 composites. This study focuses on the electrochemical performance of S–CNT, S–CNT–TiN, and S–CNT–WO3, as well as the synergetic effect of the CNT–TiN–WO3 heterostructure with different separators (GFA and Celgard) to address the polysulfide (PS) ‘shuttle effect’ and electron–ion transport by integrating WO3 and TiN as chemical absorbents and conducting catalysts, respectively. Based on the electrochemical performance, the as-synthesized 50 wt % WO3 composites paired with GF/A and Celgard separators exhibited specific discharge–charge capacities of 1512 and 1216 mAh g–1 at 0.1C-rate, respectively. After prolonged cycles (200 cycles) at 0.5C, GF/A and Celgard retained specific capacities of 689 and 522 mAh g–1, while at a 1C-rate, the capacity retentions were ∼87% and ∼47% after the 100th cycle, highlighting the superior stability of the cell with the GF/A separator. The calculated gravimetric energy densities of the two systems were 1030 and 604 Wh kg–1 after 500 cycles. Benefiting from the porous nature of the GF/A separator and the conductive routes from the heterostructure cathode, the diffusion coefficient of the device reached up to 1.4 × 10–15 cm2 s–1.