A Carbon-Cotton Cathode with Ultrahigh-Loading Capability for Statically and Dynamically Stable Lithium-Sulfur Batteries.

Abstract

Sulfur exhibits a high theoretical capacity of 1675 mA h g-1 via a distinct conversion reaction, which is different from the insertion reactions in commercial lithium-ion batteries. In consideration of its conversion-reaction battery chemistry, a custom design for electrode materials could establish the way for attaining high-loading capability while simultaneously maintaining high electrochemical utilization and stability. In this study, this process is undertaken by introducing carbon cotton as an attractive electrode-containment material for enhancing the dynamic and static stabilities of lithium-sulfur (Li-S) batteries. The carbon cotton possessing a hierarchical macro-/microporous architecture exhibits a high surface area of 805 m2 g-1 and high microporosity with a micropore area of 557 m2 g-1. The macroporous channels allow the carbon cotton to load and stabilize a high amount of active material. The abundant microporous reaction sites spread throughout the carbon cotton facilitate the redox chemistry of the high-loading/content Li-S system. As a result, the high-loading carbon-cotton cathode exhibits (i) enhanced cycle stability with a good dynamic capacity retention of 70% after 100 cycles and (ii) improved cell-storage stability with a high static capacity retention of above 93% and a low time-dependent self-discharge rate of 0.12% per day after storing for a long period of 60 days. These carbon-cotton cathodes with the remarkably highest values reported so far of both sulfur loading (61.4 mg cm-2) and sulfur content (80 wt %) demonstrate enhanced electrochemical utilization with the highest areal, volumetric, and gravimetric capacities simultaneously.