Graphene quantum dots as the nucleation sites and interfacial regulator to suppress lithium dendrites for high-loading lithium-sulfur battery

Lithium–sulfur battery is one of the most promising candidates to take over from the conventional lithium-ion batteries for the next-generation high energy storage devices. Although plausible advances have been made on the performances of the composite cathode with high sulfur loading, the development of compatible protection strategies for lithium anode is seriously lagging behind. Here we report a new strategy to suppress the dendrite growth in lithium-sulfur batteries with high sulfur loading by introducing graphene quantum dots into the electrolyte. The graphene quantum dots serve as the heterogeneous sites for uniform nucleation and provide continual regulation for the dendrite-free lithium deposition. The in-situ Raman spectroscopy reveals the enrichment of the GQDs at the electrode-electrolyte interface for the regulated electric field and ion flux, resulting in the dendrite-free Li deposition. As a result, the critical current of short circuit induced by lithium dendrite increases up to 7.44 mA cm−2, and the soft-short risk is excluded when cycling at the current density of 3 mA cm−2 with areal capacity of 3 mAh cm−2 for more than 500 h, demonstrating the excellent dendrite suppressing action of the GQDs. As a proof of concept, high-loading lithium-sulfur batteries using the GQDs-modified anolyte are fabricated with stable Coulombic efficiency of 99% at the current density of 3 mA cm−2 with sulfur loading of 4 mg cm−2 over 200 cycles. Our results provide a novel and facile approach to tackle the intrinsic problem on the lithium anode for high-loading lithium-sulfur batteries.