Graphene Foam Current Collector for High-Areal-Capacity Lithium–Sulfur Batteries

Abstract

Extending lithium–sulfur battery (LSB) electrode architecture into three dimensions (3D) has been proposed for more than a decade. A 3D lightweight and porous current collector that is capable of holding high amounts of sulfur (S) without any significant decrease in performance has been elusive. Although many material solutions (such as sulfurized polyacrylonitrile or SPAN) have been identified for alleviating polysulfide formation and the so-called shuttle effect, their incorporation into 3D current collectors with high capacity at the electrode level has not yet been realized. Here, we show that graphene foams (GFs) are ideally suited as 3D lightweight current collectors for LSBs and outperform the conventional carbon-coated Al (Al/C) foils at the electrode level. Specifically, we demonstrate that the open framework of GFs facilitates high mass loading of SPAN without any deterioration in capacity at the active material level even at high S loading. At the electrode level, GF-SPAN cathodes exhibited capacities of ∼200 mAh gelectrode–1 at 0.1C even with low S loadings (∼1.1 mg cm–2), which is at least 3 times higher than conventional Al/C electrodes. More importantly, we fabricated cells with a high mass loading of 26.5 mg cm–2 S by stacking multiple GFs to achieve an areal capacity as high as ∼20 mAh cm–2 (at a current density of 3.0 mA cm–2 up to 50 cycles), which is at least 3 times higher than LSB areal capacity (6 mAh cm–2) needed to displace LIBs.