A Shell-Shaped Carbon Architecture with High-Loading Capability for Lithium Sulfide Cathodes

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.