Hierarchical porous g-C3N4/reduced graphene oxide architecture as light-weight sulfur host material for high-performance lithium-sulfur batteries

Abstract

High–energy density lithium-sulfur (Li-S) batteries suffer from short cycling lifespan, poor rate capability, and low sulfur utilization. Here we report design and synthesis of hierarchical porous g-C3N4/reduced graphene oxide (r-GO) as light-weight sulfur host material for Li-S batteries via a poly-condensation method using silica nanoparticles as hard templates. Microstructure of the g-C3N4/r-GO architecture has been characterized. Electrochemical evaluations indicate that the g-C3N4/r-GO/S composite cathode with 75 wt% of sulfur and moderate macropore density in the host material displays the best Li-storage properties. The reversible capacity reaches 589.6 mAh g−1 after 100 cycles at a current rate of 2 C (3.35 A g−1). Especially the rate capability is excellent. Even at 3.5 C, the reversible capacity can reach 55% of the capacity at 0.2 C. This light-weight g-C3N4/r-GO architecture composed of electrical conductive r-GO layers, polar g-C3N4, and hierarchical pores is a promising sulfur host material for high-performance Li-S batteries.