Bimetallic Ni₃Fe/Ni₂Fe₂N Catalyst With Optimized d-Band Center for High-Efficiency Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) face significant challenges for practical application, primarily due to the sluggish reaction kinetics and pronounced shuttle effect of lithium polysulfides (LiPSs). This study proposes a synergistic strategy involving doping engineering and controlled nitridation-induced electronic state modulation to fabricate a Ni₃Fe/Ni₂Fe₂N composite as an efficient sulfur host material. This rational design integrates the strong catalytic activity of the metal alloy (Ni₃Fe) with the high electrical conductivity of the nitride (Ni₂Fe₂N), enabling effective anchoring and conversion of polysulfides. Density functional theory (DFT) calculations and analysis results of XAFS and XPS confirm that an upshifted d-band center and modulated electronic states significantly enhance reaction kinetics and catalytic activity. In situ Raman spectroscopy and DRT analysis directly demonstrate the exceptional capability of the material to suppress the polysulfide shuttle effect. The battery exhibits remarkable cycling stability, achieving 1000 cycles with an ultralow decay rate of 0.045% per cycle. The outstanding performance is retained even under conditions as harsh as a high sulfur loading (4.3 mg cm^-2) and low temperature (-10°C). This work not only presents a high-performance catalyst but also provides new insights into the design of LSB catalysts via electronic state modulation.