Enhanced Electrochemical Kinetics on Ni₂P Polar Mediators Integrated with Graphene for Lithium–Sulfur Batteries

Lithium-sulfur batteries have evoked intensive attention caused by the urgent requirement of energy storage devices with higher energy density, long cycle life, and low cost. However, the insulating nature and the soluble reaction intermediate products still hinder its large-scale industry and acceptance by the market. Tremendous efforts focus on the composite of polar material and non-polar material to solve the weaknesses of material insulating nature and soluble reaction intermediate products. However, the linkage form between these two generic materials has been ignored. In this paper, by using typical Ni₂P as polar material and graphene as non-polar material, the reaction kinetics changes and its intrinsic theories on behavior enhancement have been proved, which construct different binding type between polar and non-polar materials. The Ni₂P/PrGO delivers an improved high specific capacity of 1254.6 mAh g^-1 than Ni₂P/rGO at 0.2 C. The relevant X-ray photoelectron spectroscopy result and the in situ electrochemical impedance spectroscopy tests prove that the linkage state between polar and non-polar material has strong influence on the sulfur cathode reaction kinetics. The enhanced reaction kinetics and polar adsorption behavior bring the soft pack battery testing unit over 150 stable cycles with decay ratio of 0.19% for each cycle.