Stable Lithium–Sulfur Cell Separator with a High-Entropy Metal Oxide Modification

Sulfur is attractive for use as a sustainable high-capacity cathode in rechargeable lithium batteries because of its natural abundance and high theoretical charge-storage capacity of 1675 mAh g–1. However, the commercialization of lithium–sulfur batteries is hampered by their challenging electrochemical characteristics (i.e., poor cycle stability and charge–discharge rate performance). Herein, a (CrMnFeNiMg)3O4 high-entropy metal oxide (HEMO) with polysulfide adsorption/conversion capabilities is used to fabricate a HEMO-modified separator to counteract the loss of active material in lithium–sulfur cells. This HEMO is synthesized by a facile hydrothermal method and used to build a HEMO-modified separator for lithium–sulfur cells. This provides lithium–sulfur cells with strong polysulfide adsorption and conversion capabilities, thereby effectively slowing their loss of active material during long cycling and their increase in polarization during high rate operation. Therefore, the cell with the HEMO-modified separator exhibits a high charge-storage capacity of 990 mAh g–1 and a high charge–discharge rate performance from C/20 to 1C while maintaining high electrochemical stability and reversibility. Given the promising electrochemical sulfur utilization and reaction capabilities of this cell, it is also evaluated at rates of C/10, C/2, and 1C, at which it exhibits high charge-storage capacities of 817, 689, and 585 mAh g–1, respectively, and long-term stability after 200 cycles while maintaining excellent capacity retention of 87, 81, and 71%, respectively.