A Facile, Low-Cost Hot-Pressing Process for Fabricating Lithium-Sulfur Cells with Stable Dynamic and Static Electrochemistry.

Lithium-sulfur batteries are among the most promising low-cost, high-energy-density storage devices. However, the inability to host a sufficient amount of sulfur in the cathode while maintaining good electrochemical stability under a lean electrolyte condition has limited the progress. The main cause of these challenges is the sensitivity of the sulfur cathode to the cell-design parameters (i.e., the amount of sulfur and electrolyte) and the experimental testing conditions (i.e., cycling rates and analysis duration). Here, a hot-pressing method is presented that effectively encapsulates a high amount of sulfur in the cathode within only 5 s, resulting in high sulfur loading and content of, respectively, 10 mg cm-2 and 65 wt%. The hot-pressed sulfur (HPS) cathodes exhibit superior dynamic and static electrochemical performance under a broad cycling-rate (C/20-1C rates) and low electrolyte/sulfur ratio (6 µL mg-1 ) conditions. The dynamic cell stability is demonstrated by high gravimetric and areal capacities of, respectively, 415-730 mAh g-1 and 7-12 mAh cm-2 at C/20-1C rates with a high capacity retention of over 70% after 200 cycles. The static cell stability is demonstrated by excellent shelf life with low self-discharge and stable cycle life on storing for over one year.