Hierarchical multi-channels conductive framework constructed with rGO modified natural biochar for high sulfur areal loading self-supporting cathode of lithium-sulfur batteries

Abstract

The insulation of sulfur and Li2S/Li2S2 (discharge products) and the “shuttle” of soluble lithium polysulfides (LiPSs) seriously limit the research of high specific capacity lithium-sulfur (Li-S) batteries with high sulfur loading. Inspired by the natural architecture of pomelo peels, we report a self-supporting carbon framework (SCF) modified by reduced graphene oxide (rGO) as conductive skeleton and sulfur carrier for the cathode of rechargeable Li-S batteries. The high initial capacity (1489.65 mA h g−1) of SCF@rGO/S binder-free cathode with the high sulfur areal loading (∼5.50 mg cm−2) arise from the improved batteries conductivity by the interconnecting conductive skeleton. The SCF@rGO with hierarchical porous structure, abundant microchannels and oxygenic functional groups can effectively physical limit/intercept and chemical adsorption/anchor LiPSs, thereby improving the utilization of active sulfur and promoting the reuse. Sufficient active sites in SCF@rGO/S provide close electrical contact to accelerate electrons and ions transfer, resulting in high electrochemical activity and redox kinetics. Consequently, the SCF@rGO/S cathode exhibits an outstanding capacity retention (569.66 mA h g−1) and cycle stability at 1 C for over 200 long-term cycles with a decline of only 0.13% per cycle. Even at 2 C, the capacity is still up to 645.59 mA h g−1. The SCF@rGO/S cathode provide a feasible approach and strategy to develop high performance Li-S batteries.

Keywords

• Lithium-sulfur battery
• Self-supporting cathode
• Conductive framework
• High sulfur areal loading
• Electrochemical performance