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Lithium sulfide (Li2S) is considered a highly attractive cathode for establishing high-energy-density rechargeable batteries, especially due to its high charge-storage capacity and compatibility with lithium-metal-free anodes. Although various approaches have recently been pursued with Li2S to obtain high performance, formidable challenges still remain with cell design (e.g., low Li2S loading, insufficient Li2S content, and an excess electrolyte) to realize high areal, gravimetric, and volumetric capacities. This study demonstrates a shell-shaped carbon architecture for holding pure Li2S, offering innovation in cell-design parameters and gains in electrochemical characteristics. The Li2S core-carbon shell electrode encapsulates the redox products within the conductive shell so as to facilitate facile accessibility to electrons and ions. The fast redox-reaction kinetics enables the cells to attain the highest Li2S loading of 8 mg cm−2 and the lowest electrolyte/Li2S ratio of 9/1, which is the best cell-design specifications ever reported with Li2S cathodes so far. Benefiting from the excellent cell-design criterion, the core-shell cathodes exhibit stable cyclability from slow to fast cycle rates and, for the first time, simultaneously achieve superior performance metrics with areal, gravimetric, and volumetric capacities. [ABSTRACT FROM AUTHOR]

As a primary component in lithium-sulfur (Li-S) batteries, the separator may require a custom design in order to facilitate electrochemical stability and reversibility. Here, a custom separator with an activated carbon nanofiber (ACNF)-filter coated onto a polypropylene membrane is presented. The entire configuration is comprised of the ACNF filter arranged adjacent to the sulfur cathode so that it can filter out the freely migrating polysulfides and suppress the severe polysulfide diffusion. Four differently optimized ACNF-filter-coated separators have been developed with tunable micropores as an investigation into the electrochemical and engineering design parameters of functionalized separators. The optimized parameters that are verified by electrochemical and microstructural analyses require the coated ACNF filter to possess the following: (i) a porous architecture with abundant micropores, (ii) small micropore sizes, and (iii) high electrical conductivity and effective electrolyte immersion. It is found that the ACNF20-filter-coated separator demonstrates an overall superior boost in the electrochemical utilization (discharge capacity: 1270 mA h g−1) and polysulfide retention (capacity fade rate: 0.13% cycle−1 after 200 cycles). These results show that the modified thin-film-coating technique is a viable approach to designing ultratough ACNF-filter-coated separators with outstanding mechanical strength and flexibility as an advanced component in Li-S cells. [ABSTRACT FROM AUTHOR]

In article number 1500738, Arumugam Manthiram and co‐workers report the design of a custom separator with an activated carbon nanofiber (ACNF) filter coating on a polypropylene membrane. The entire configuration is composed of the ACNF‐filter coating arranged adjacent to the sulfur cathode so that it can suppress polysulfide diffusion. A comparative analysis of four differently optimized ACNF‐filter‐coated separators provides insight into the polysulfide‐trapping mechanism and demonstrates an overall boost in the cell performance. [ABSTRACT FROM AUTHOR]