Minimizing the Electrolyte Volume in Li-S Batteries: A Step Forward to High Gravimetric Energy Density

Sulfur electrodes confined in an inert carbon matrix show practical limitations and concerns related to low cathode density. As a result, these electrodes require a large amount of electrolyte, normally three times more than the volume used in commercial Li-ion batteries. Herein, a high-energy and high-performance lithium-sulfur battery concept, designed to achieve high practical capacity with minimum volume of electrolyte is proposed. It is based on deposition of polysulfide species on a self-standing and highly conductive carbon nanofiber network, thus eliminating the need for a binder and current collector, resulting in high active material loading. The fiber network has a functionalized surface with the presence of polar oxygen groups, with the aim to prevent polysulfide migration to the lithium anode during the electrochemical process, by the formation of S-O species. Owing to the high sulfur loading (6 mg cm-2) and a reduced free volume of the sulfide/fiber electrode, the Li-S cell is designed to work with as little as 10 µL cm-2 of electrolyte. With this design the cell has a high energy density of 450 Wh kg-1, a lifetime of more than 400 cycles, and the possibility of low cost, by use of abundant and eco-friendly materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim