Synergistic catalysis and adsorption in Nb-CoxSe8/NC: Enabling high-performance lithium-sulfur battery with functional separator

Lithium‑sulfur (Li-S) batteries possess great theoretical specific capacity and energy density, low cost, and better safety, thus, they are deemed to be very promising batteries. However, they have also low active material utilization, shuttle effect, and volume expansion problems, which have brought serious obstacle to the commercial development of Li-S batteries. These problems can be refined via modifying polypropylene (PP) diaphragm. In this work, we design a heterostructure consisting of nitrogen-doped carbon (NC), metal niobium (Nb), and Co x Se 8 (Co 9 Se 8 and Co 6.8 Se 8 ) to modify PP. According to density functional theory (DFT) calculations, the presence of Nb in Nb-Co x Se 8 /NC results in fortified catalytic conversion capability toward lithium polysulfides (LiPSs). Furthermore, Co x Se 8 adsorbs the LiPSs to a substantial extent, mitigating the shuttle effect, which leads to enhanced use of the active substance during charging and discharging reactions. Simultaneously, the porous architecture mitigates the expansion in sulfur's volume. The electrochemical test consequence depicts that Li-S battery with Nb-Co x Se 8 /NC-PP diaphragm has a primary discharge capacity of 1449 mAh g −1 at 0.5 C, with a capacity retention rate of 68% after 100 cycles. It has also an initial discharge capacity of 868 mAh g −1 at 10 C in the rate performance test. Even with a high areal loading of 3.1 mg cm −2 , Li-S battery delivers an adequate electrochemical functionality. This study provides an idea for constructing heterostructured metal selenides to improve the electrochemical functionality of Li-S batteries.