Porous honeycomb-like C3N4/rGO composite as host for high performance Li-S batteries

Abstract

Lithium-sulfur (Li-S) batteries have attracted extensive attention along with the urgent increasing demand for energy storage owing to the high theoretical specific capacity and energy density, abundant reserves and low cost of sulfur. However, the practical application of Li-S batteries is still impeded due to the low utilization of sulfur and serious shuttle-effect of lithium polysulfides (LiPSs). Here, we fabricated the porous honeycomb-like C3N4 (PHCN) through a hard template method. As a polar material, graphitic C3N4 has abundant nitrogen content (∼58%), which can provide enough active sites to mitigate shuttle-effect, and then conductive reduced graphene oxide (rGO) was introduced to combine with PHCN to form PHCN/rGO composite in order to improve the utilization efficiency of sulfur. After sulfur loading, the PHCN/rGO/S cathode exhibited an initial discharge capacity of 1,061.1 mA h g−1 at 0.2 C and outstanding rate performance at high current density of 5 C (495.1 mA h g−1), and also retained 519 mA h g−1 after 400 cycles at 1 C. Even at high sulfur loading (4.3 mg cm−2), the capacity fade rate was only 0.16% per cycle at 0.5 C for 200 cycles. The above results de monstrate that the special design of PHCN/rGO composite as sulfur host has high potential application for Li-S rechargeable batteries.