Net-Structured Filter of Co(OH)<sub>2</sub>‑Anchored Carbon Nanofibers with Ketjen Black for High Performance Li–S Batteries

Lithium sulfur batteries have been extensively explored in recent years owing to their high theoretical energy density (∼2600 Wh kg<sup>–1</sup>), environmental benignity, and low cost of raw materials. Besides the advanced sulfur cathode, various functional separators/interlayers are also being developed as the effective inhibitor of polysulfide diffusion. In this study, Co­(OH)<sub>2</sub>-anchored carbon nanofibers (CNFs) with Ketjen black (KB) dispersed in the void were designed as a dense net-like structure (denoted as Co­(OH)<sub>2</sub>@CNF/KB), which was coated at the surface of a typical commercial separator to help inhibit polysulfide migration. It was demonstrated that the Co­(OH)<sub>2</sub>@CNF/KB-modified separator could effectively increase the charge transfer of the cathode material, trap the dissolved polysulfides, and help to reuse the sequestered active material. As a result, the cell employing this functionalized separator and unmodified sulfur-based electrode exhibits an initial specific capacity of 1394 mA h g<sup>–1</sup> at 0.1 C, which converts to 84% utilization of sulfur, and a capacity decay of 0.10% per cycle at 2 C for over 450 cycles. The unique design of Co­(OH)<sub>2</sub>@CNF/KB provides a promising modifying approach for future lithium batteries.