High-performance nitrogen-doped titania nanowire decorated carbon cloth electrode for lithium-polysulfide batteries

Integrated Design of Interlayer/Current-Collector: Heteronanowires Decorated Carbon Microtube Fabric for High-Loading and Lean-Electrolyte Lithium-Sulfur Batteries

Low sulfur loading, high electrolyte/sulfur (E/S) ratio, and sluggish sulfur redox reaction are the main challenges that severely impede the practical application of lithium-sulfur batteries (LSBs). To address these problems, a self-standing hollow carbonized cotton cloth (CCC) decorated with TiO₂ -TiN heteronanowires (CCC@TiO₂ -TiN) is proposed to replace the traditional cathode. Concretely, one side of CCC@TiO₂ -TiN serves as a current-collector to load sulfur (CCC@TiO₂ -TiN/S), while the other side facing the separator acts as interlayer to inhibit shuttle effect. This advanced intergrated interlayer/current-collector cathode is endowed with excellent 3D electron/ion transportation, a strong confinement barrier, and vast sulfur loading sites. Moreover, the as-developed TiO₂ -TiN heteronanowires work as in situ capture and catalysis sites for the reversible and accelerated sulfur redox reaction. Therefore, the intergrated cathode of CCC@TiO₂ -TiN/S achieves an ultrahigh sulfur loading of 13 mg cm^-2 and delivers a superb areal capacity of 9.09 mAh cm^-2 under the ultralow E/S ratio of 4.6 µL mg^-1 . This work provides a new model material to achieve high sulfur loading and lean-electrolyte toward the practical LSBs with high specific energy density.

Revisiting the positive roles of liquid polysulfides in alkali metal-sulfur electrochemistry: from electrolyte additives to active catholyte

Polysulfide dissolution and shuttling in liquid organic electrolytes are considered as the most challenging detrimental effects of an Li-S cell, which is one of the most promising next-generation high-energy-density batteries. Therefore, considerable efforts have been devoted to confining solid sulfur or sulfide so as to avoid the formation and diffusion of dissolved polysulfides. However, the positive roles played by the liquid polysulfides in Li-S electrochemistry should not be overlooked. Polysulfide dissolution can promote the cell kinetics and sulfur utilization; as electrolyte additives, polysulfides can help stabilize the Li metal anode, redistribute the active mass in the cathode and act as extra back-up active sulfur sources. After being applied directly as active catholytes, a novel Li-polysulfide redox flow battery (Li-PS RFB) and an Li-polysulfide battery (Li-PS battery) have been developed. This review revisited these beneficial effects of polysulfides and provided a summary of the recent progress on Li-PS RFB and Li-PS batteries, especially with a more comprehensive emphasis on the latter. Furthermore, dissolved polysulfides applied as active catholytes in Na-S and K-S systems and as catholytes or anolytes in aqueous batteries were also briefly discussed. Hopefully, the Li-S electrochemistry can be better understood so as to overcome challenging issues in the way of the practical commercialization of the Li-S batteries.