Freestanding cellulose paper-derived carbon/Fe/Fe3C with enhanced electrochemical kinetics for high-performance lithium-sulfur batteries

The loss and sluggish kinetics of intermediate polysulfides in electrochemical processes seriously reduce electrochemical activity of sulfur in lithium-sulfur batteries (LSBs). Herein, we design and synthesize freestanding graphitized carbon interlayers decorated with Fe/Fe3C nanocatalysts by thermal treatment of cellulose paper with adsorbed ferric nitrate at 1000 degrees C, during which the freestanding carbon network derives from the cellulose paper while the Fe results from the reduction of Fe3+ with a carbothermal reduction process; simultaneously, the in situ formed Fe boosts graphitization of carbon to enhance electrical conductivity of the interlayer, and the carbon network effectively helps confine and accommodate Fe/Fe3C nanoparticles. Therefore, the well dispersed Fe/Fe3C nanoparticles catalytically accelerate electrochemical conversion of polysulfides, while the enhanced conductive network of carbon benefits the electron transfer during the electrocatalytic process. The cell with an optimal carbon/Fe/Fe3C interlayer delivers excellent cyclability and rate performances. At current densities of 0.2C and 2C, the specific capacities are close to 1000 and 735mA h g(-1), respectively. Even after 200 cycles at 1C, the reversible specific capacity is still 772mA h g(-1). Such a synergistic catalytic interlayer with an enhanced conversion kinetic towards polysulfides provides a new approach for improving electrochemical performances of LSBs. (C) 2019 Elsevier Ltd. All rights reserved.