Probing Sulfur Deposition onto Carbon Nanomaterials from Aqueous, Elemental Sulfur Sols for Lithium–Sulfur Batteries

Abstract

Sulfur cathodes for lithium–sulfur batteries often rely on integrating sulfur with high surface area carbonaceous materials. Nanoscale mixing is typically achieved by a lengthy, high-temperature melt imbibition approach that employs carbon nanomaterials in an aggregated solid form. In this work, we present a simple strategy to coat carbon nanomaterials with sulfur in a cost-effective, room-temperature process using inexpensive elemental sulfur. Our results are based on hydrophobic sulfur sols, which have rarely been examined for use in the preparation of sulfur cathodes. We study the deposition mechanism on different carbon materials and find that sulfur dissolves from the sol into the aqueous phase and coats the surface of reduced graphene oxide (rGO) by heterogeneous nucleation and growth, but that this mechanism is not favored for carbon materials such as Ketjen black (KB) and graphene oxide (GO), for which undesirable homogeneous nucleation of micron-sized, insulating sulfur crystals is observed. High loading (3–4 mgsulfur/cm2) rGO-based cathodes prepared using this approach achieve discharge capacities of 1300 mAh/gsulfur (∼4.8 mAh/cm2) at 0.1C and achieve capacities 7-fold higher than cells prepared via traditional melt imbibition approaches at higher rates of 0.8C and 1C. Cells prepared without the need for added binder or conductive additive achieve projected full cell energy densities of 468 Wh/kg at 0.1C when taking into account all inactive components and assuming no lithium metal degradation, indicating that the deposition of sulfur from hydrophobic sols onto carbon nanomaterials can serve as a simple, aqueous-based, one-step process to prepare high sulfur loading cathodes with high projected energy densities.

Evaluating the effectiveness ofin situcharacterization techniques in overcoming mechanistic limitations in lithium–sulfur batteries

“…210 However, sulfur is sensitive to the high energy electron beam and high vacuum and sublimation, making the imaging of sulfur with TEM very challenging. 211 The setup for in situ TEM is the same in most of the studies, with some minor variations. It generally consists of a holder with a working electrode normally sulfur coated with a conductive coating to prevent sulfur sublimation under high vacuum and high energy electron beam conditions.…”

Fluorinated Graphite (FG)-Modified Li–S Batteries with Superhigh Primary Specific Capacity and Improved Cycle Stability

“…Nevertheless, challenges still exist and limit their further application . On the one hand, sulfur suffers from poor electronic conductivity and dramatic volume variation upon cycling. , On the other hand, soluble lithium polysulfide intermediates can diffuse out of the cathode, leading to the loss of active substance, low Coulombic efficiency, and fast capacity decay. − In addition, lithium metal anode suffers from potential safety hazards from dendrites. − In recent years, many kinds of functional materials have been designed as host materials for Li–S batteries. − Physical confinement, capillary adsorption, and chemical bonding are recognized as available methods to restrain the shuttle effect. − However, most of the functional host materials are limited by low sulfur loading, which is disadvantageous for practical applications.…”