NiFeP Anchored on Rgo As a Multifunctional Interlayer to Promote the Redox Kinetics for Li–S Batteries Via Regulating D-Bands of Ni-Based Phosphides

Sluggish kinetics of polysulfide redox reaction give rise to poor electrochemical properties for lithium-sulfur (Li-S) batteries. Electrocatalysts are introduced to decrease activation energy and effectively accelerate the dynamics of polysulfide conversion. In this study, we propose a rational strategy of tuning the d-band of catalysts via delivering Fe into Ni2P in situ grown on rGO to construct NiFeP/rGO composites. Based on the first-principles density functional theory calculation, the metallic conduction of Ni2P could be improved by Fe incorporation, facilitating a charge transfer electrocatalytic interface for redox reaction of LiPSs. Moreover, the d-band center of NiFeP also elevates to the Fermi level after incorporation with Fe, which could weaken the S-S bonds of polysulfides due to its redistributed electron population and reduce the activation barrier. Therefore, NiFeP/rGO composites as the functional interlayer for Li-S batteries can not only promote the interaction between polysulfides and NiFeP but also accelerate the conversion of polysulfides. They exhibit a high initial discharge capacity of 1261 mAh g-1 at 0.2 C and an outstanding rate reversible capacity of 671 mAh g-1 even at a high rate of 2 C. The high-efficiency NiFeP/rGO electrocatalyst with a rational structure for Li-S batteries testifies to the availability of the d-band regulating strategy with the low-activation-energy barrier and promotes an in-depth understanding of LiPSs redox reaction at the molecular or atom level.