Lithium-sulfur batteries have great potential to satisfy the increasing demand of energy storage systems for portable devices, electric vehicles, and grid storage because of their extremely high specific capacity, costeffectiveness, and environmental friendliness. In spite of all these merits, the practical utilization of lithium-sulfur batteries is impeded by commonly known challenges, such as low sulfur utilization (<80%), short life (<200 cycles), fast capacity fade, and severe self-discharge effect, which mainly result from the i) low conductivity of the active material, ii) serious polysulfide shuttling, iii) large volume changes, and iv) lithium-metal anode contamination/corrosion. Numerous approaches are reported to effectively mitigate these issues. Indeed, such approaches have shown enhanced lithium-sulfur battery performances. However, many reports overlook the critical parameters, including sulfur loading (<13 mg cm −2 ), sulfur content (<70 wt%), and electrolyte/sulfur ratio (>11 µL mg −1 ), that significantly affect the analyzed electrochemical characteristics, energy density, and practicality of lithium-sulfur batteries. This review highlights the trends and progress in making cells fulfilling these fabrication parameters and discuss the challenges of the amount of sulfur and electrolyte in fabricating cells with practically necessary parameters and with high electrochemical utilization and efficiency.

Sulfur exhibits a high theoretical capacity of 1675 mA h g 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 m g and high microporosity with a micropore area of 557 m g. 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) and sulfur content (80 wt %) demonstrate enhanced electrochemical utilization with the highest areal, volumetric, and gravimetric capacities simultaneously.

The design of a core–shell sulfur cathode demonstrates superior dynamic and static stability at a high sulfur loading in Li–S batteries.

A custom single-wall carbon nanotube (SWCNT)-modulated separator is employed to directly suppress the polysulfide migration and indirectly protect the lithium-metal anode from severe polysulfide contamination. The conductive sp(2) -carbon scaffold continuously reactivates and reutilizes the trapped active material, so the SWCNT-modulated separator provides a facile way to facilitate the implementation of pure sulfur cathodes with high sulfur contents and loadings.