MOFs-derived nitrogen-doped carbon interwoven with carbon nanotubes for high sulfur content lithium–sulfur batteries

Abstract

Despite their high energy density, low-cost, and low environmental impacts compared with the current state-of-the-art lithium-ion batteries, lithium–sulfur (LiS) batteries still suffer from the low sulfur content, dissolution of polysulfides and capacity loss, which hinder their commercial application. To address these issues, nitrogen-doped cubic carbon (NC) interwoven with carbon nanotubes (CNT) host is introduced to achieve high sulfur content for lithium–sulfur batteries. The NC/CNT composites are derived from metal–organic frameworks (MOFs), which can physically confine sulfur, thus providing efficient sulfur loading. The sulfur content in the as-obtained S@NC/CNT composite is as high as 89 wt%, while the cathode membrane has a sulfur loading of 3.6 mg cm−2. In addition, the NC/CNT composite can obstruct the dissolution and outward diffusion of polysulfides. Impressively, under the high sulfur content and high sulfur loading conditions, the S@NC/CNT cell exhibits initial specific capacity of 1141 mA h g−1 at the current rate of 0.5C (837.5 mA g−1) and the capacity retains 674.4 mA h g−1 after 120 cycles. The S@NC/CNT cathode also shows high areal capacity (4.1 mA h cm−2). The NC/CNT composite derived from MOFs has great potential applications for high‑sulfur loading cathodes.