Reducing Overpotential of Solid‐State Sulfide Conversion in Potassium‐Sulfur Batteries

Abstract

Improving kinetics of solid-state sulfide conversion in sulfur cathodes can enhance sulfur utilization of metal-sulfur batteries. However, fundamental understanding of the solid-state conversion remains to be achieved. Here, taking potassium-sulfur batteries as a model system, we for the first time report the reducing overpotential of solid-state sulfide conversion via the meta-stable S 3 2À intermediates on transition metal single-atom sulfur hosts. The catalytic sulfur host containing Cu single atoms demonstrates high capacities of 1595 and 1226 mAh g À 1 at current densities of 335 and 1675 mA g À 1 , respectively, with stable Coulombic efficiency of � 100 %. Combined spectroscopic characterizations and theoretical computations reveal that the relatively weak Cu-S bonding results in low overpotential of solid-state sulfide conversion and high sulfur utilization. The elucidation of solid-state sulfide conversion mechanism can direct the exploration of highly efficient metal-sulfur batteries.

Rechargeable Metal-Sulfur Batteries: Key Materials to Mechanisms

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Two-dimensional MXenes for flexible energy storage devices

“…399 However, the performance of KSBs to date has not been satisfying because uneven K deposition enlarges the reaction area with soluble intermediate products, aggravating shuttling and deteriorating cell performance. 400,401…”

Strong d−π Orbital Coupling of Co–C4 Atomic Sites on Graphdiyne Boosts Potassium–Sulfur Battery Electrocatalysis

“…Potassium–sulfur (K–S) batteries are receiving great attention for large-scale energy storage due to their high energy density (1023 Wh kg –1 ), high element abundance (both potassium and sulfur), environmental benignity, and low cost. − However, further advancement of K–S batteries has encountered challenges associated with volume expansion and electronic insulation nature of sulfur, the shuttle effect of potassium polysulfide, and sluggish kinetics. − Compared to the inseparable low-order polysulfides in Li/Na–S batteries, K–S batteries have explicit cathode electrochemistry, which involves both solution-phase and solid-phase processes. − Among them, the solid-phase K 2 S 3 /K 2 S 2 to K 2 S process delivers over 60% of the theoretical capacity; however, in reality, the excessively high reaction barrier and the discharge production of “dead” sulfur species (partial K 2 S) induce significant capacity loss for the K–S batteries . Therefore, the sluggish kinetics of the K 2 S 3 /K 2 S 2 to K 2 S conversion has become one of the grand challenges affecting the capacity, rate ability, and capacity retention of K–S batteries. , To solve this problem, intermetallics, metal nanoparticles, single-atom catalysts, and homogeneous catalysts have been explored as potassium polysulfide catalysts, aiming to facilitate the conversion of sulfur. − Despite these endeavors, the solid-state conversions of K 2 S 3 /K 2 S 2 to K 2 S are still sluggish, and the respective mechanism remains elusive, which collectively restrict further advancement of K–S batteries. Therefore, the search for new-concept cathodes with much improved catalytic activities toward the solid-state conversions of K 2 S 3 /K 2 S 2 to K 2 S is highly desirable, yet remains a grand challenge.…”