Nitrogen-Doped Graphene Quantum Dots: Sulfiphilic Additives for the High-Performance Li-S Cells

The lithium-sulfur cell is considered to be the most promising next-generation energy storage system. However, the practical use of Li-S batteries is hindered by several problems such as poor cycle retention, low Coulombic efficiency, low sulfur loading, and so forth. We herein for the first-time propose nitrogen-doped graphene quantum dots as the sulfiphilic additive for the advancement of Li-S cell performance. We carry out direct decoration of conducting additives and carbon cloth interlayers with graphene quantum dots and nitrogen-doped graphene quantum dots, which are evaluated in Li-S cells. Nitrogen-doped graphene quantum dots exhibit strong sulfiphilic properties, and therefore, they anchor the liquid-phase polysulfides. The Li-S cell using the nitrogen-doped graphene quantum dot-decorated carbon cloth interlayer shows a discharge capacity of 1454.4 mA h g(S)(-1) at 0.1 C and a capacity retention of 98.2% at 0.5 C after 300 cycles even with a sulfur loading of 6.0 mg S cm(-2). Our study demonstrates that the nitrogen-doped graphene quantum dot is a promising additive, which can improve the viability of Li-S cells for the next generation of energy storage systems.