The d‐band energy level splitting of ferric group (Fe, Co, Ni) metals drives the adsorption‐conversion of polysulfides

Abstract

AbstractThe notorious lithium polysulfides (LiPSs) shuttle effect, which results in low capacity, subpar rate performance, and quick capacity deterioration, has severely restricted the practical applications of lithium sulfur (Li‐S) batteries. Therefore, it is very important for modified materials to promote thermodynamics and redox kinetics in the entrapping‐conversion process of polysulfides. Density functional theory (DFT) calculations show that ferric group (Fe, Co, Ni) transition metals not only provide moderate binding contacts with LiPSs but also act as an active catalyst in the spontaneous and sequential lithiation of S8 to Li2S by d‐band energy level splitting, and quick migration of Li ions can be operated on their surface, enhancing the utilization of LiPSs. Experimentally, felicitously‐fabricated ferric group (Fe, Co, Ni) transition metals encapsulated in nitrogen‐doped carbon nanotubes (M@NCNT) electrocatalysts were introduced into Li‐S batteries via separator functionalization. Actually, the experiments demonstrated that the excellent shuttle effect hindering was enabled. Consistent with theoretical predictions, Li‐S batteries with Ni@NCNT modified separators had significantly improved rate capacity and cycling stability. The cells with Ni@NCNT were able to achieve a high initial discharge capacity of 1035 mAh g−1 and a capacity retention rate of 70% at 500 discharges at 1.0 C with a 0.060% capacity decay each cycle, performing considerable cycle‐life with state‐of‐the‐art separators. Our work demonstrated a realistic separator‐modified strategy of d‐band energy level splitting from ferric group metals for high‐performance and long‐life Li‐S batteries, further propelling Li‐S battery commercialization.