Electronically Modulated NiFeP for Efficient Sulfur Reodx in Lithium-Sulfur Batteries

Abstract

The practical deployment of lithium–sulfur （Li–S） batteries is largely restricted by the shuttle effect of soluble lithium polysulfides （LiPSs）, sluggish sulfur redox kinetics, and inefficient liquid–solid conversion from LiPSs to Li2S, resulting in limited sulfur utilization and rapid capacity decay. To address these issues, an electronically tuned NiFeP nanorod interlayer is introduced as a multifunctional catalytic mediator for Li–S batteries. The interconnected NiFeP nanorods provide continuous charge-transfer pathways and abundant catalytic interfaces, while Fe incorporation tailors the electronic structure of the Ni–P framework and induces charge redistribution. These features strengthen LiPS immobilization, accelerate polysulfide redox conversion, and facilitate Li2S nucleation/growth. X-ray photoelectron spectroscopy confirms the electronic interaction between NiFeP and LiPSs, and in situ Raman spectroscopy reveals rapid S8 consumption and early polysulfide formation during discharge. Potentiostatic discharge analysis further demonstrates enhanced Li2S deposition, with a shortened nucleation time of 955 s and a high deposition capacity of 1056.9 mAh g-1. Leveraging the regulated polysulfide conversion pathway, the NiFeP interlayer delivers a high discharge capacity of 1100 mAh g-1 at 1 C. It maintains stable cycling performance over 500 cycles, retaining 543.4 mAh g-1 with a low fading rate of 0.053% per cycle. Furthermore, pouch-type Li–S cells with the NiFeP interlayer exhibit stable cycling performance at 0.1 C, delivering an initial capacity of approximately 1038 mAh g-1 and maintaining over 650 mAh g-1 after 140 cycles. The practical applicability of the NiFeP interlayer is further demonstrated by a pouch-type Li–S cell successfully powering a commercial electric fan. This study demonstrates that electronic regulation of bimetallic phosphides is a viable approach for modulating sulfur redox chemistry and improving the electrochemical performance and practical feasibility of Li–S batteries.