Electrochemical coverage of reduced graphene oxide layers on sulfur supported by biochar for enhancing performance of Li-S battery

Abstract

To improve the electrochemical performance of Li-S batteries, a cathodic material (rGO₁₅₀/S/CF-75) was fabricated for Li-S batteries by adopting a melt-flow method to load sulfur on biomass-derived carbon fibers, then the reduced graphene oxide was electrochemically covered on the outside surface of the sulfur. The coverage of reduced graphite oxide layers endows the performance of S/CF-75 multiple improvements. The specific capacity of rGO₁₅₀/S/CF-75 cathode delivers a specific capacity of 1451.4 mAh g^-1 at 0.1 A g^-1. The specific capacity of rGO₁₅₀/S/CF-75 cathode can still maintain 537.3 mAh g^-1 after 1000 cycles at 5 A g^-1 (109 % capacity retention). The excellent performance of rGO₁₅₀/S/CF-75 cathode is benefit from not only the conductive paths of reduced graphene oxide layers and protective function of reduced graphene oxide layers inhibiting that the soluble sulfur diffuse into bulk electrolyte, but also the redistribution of sulfur on conductive carbon components during the cycling process.

Keywords: Li-S battery; Redistribution of sulfur; Reduced graphene oxide; S/carbon fibers.