High sulfur content and volumetric capacity promised by a compact freestanding cathode for high-performance lithium–sulfur batteries

Abstract

The freestanding sulfur cathodes have achieved high areal capacity and cycling stability, but low sulfur content and volumetric capacity have greatly offset their advantages in high-energy-density lithium-sulfur (Li–S) batteries. Herein, nitrogen-doped porous carbon nanofibers with hierarchical pore structure and long-range conductivity were prepared by facile electrospinning method and subsequent pyrolysis in the N2 atmosphere. Benefiting from high specific surface area, large pore volume, rational nitrogen configuration and interwoven conductive network when directly used as freestanding sulfur composite cathodes, the resultant electrodes have exhibited high areal capacity, large volumetric capacity and good cycling stability even under high sulfur content and high sulfur loading. At sulfur content of 85 ​wt% and sulfur loading of 14.3 ​mg ​cm−2, the electrode delivers high areal capacity of 10.4 ​mA ​h ​cm−2 and volumetric capacity of 904 ​mA ​h ​cm−3 at high current density of 4.8 ​mA ​cm−2. The electrochemical performance ranks it among the state-of-the-art those in the carbon-based sulfur cathodes. This work opens a new avenue for the development of high-energy-density and long-life Li–S batteries based on the freestanding conductive hierarchical porous nanoarchitectures.