Oxygen-doped carbon nanofiber nonwovens as an effective interlayer towards accelerating electrochemical kinetics for lithium-sulfur battery

Abstract

Introduction of hydrophilic groups like oxygen/nitrogen groups is considered as a favorite solution to guarantee the functionality for interlayer in lithium-sulfur battery. However, the contributions of different oxygen containing groups was less studied especially when carbon nanofibers are used as interlayer. Herein, a bifunctional electrospun carbon nanofiber nonwoven (xO-CM) derived from coal tar pitch was prepared, followed by acid impregnation. The species and amount of oxygen groups could be finely regulated by changing the acid oxidation time. When xO-CM was adopted as interlayer, increased lithiophilicity on account of oxygen doping enables a larger flux and a uniform release of lithium ions. Ex-situ EIS analysis revealed that the addition of xO-CM in the cell could accelerate the conversion between polysulfides, especially for the liquid–solid and solid–solid reaction. Besides, the oxygen doping facilitated the nucleation of Li2S. Cells with 30O-CM (acid dipping for 30 min) possessed the best facilitation with relatively low solid electrolyte interface resistance and charge transfer resistance. Even at 2C, the cell achieved an ultralow capacity decay rate of 0.06 %, demonstrating its efficatively anchoring and accelerating effect for polysulfides. This work manifested the effective mechanism of oxygen doping for lithium-sulfur battery by adopting pitch-based carbon nanofibers as carrier.