Sandwich-Like Ultrathin TiS_2 Nanosheets Confined within N, S Codoped Porous Carbon as an Effective Polysulfide Promoter in Lithium-Sulfur Batteries

摘要

As the lightest member of transition metal dichalcogenides, 2D titanium disulfide (2D TiS2) nanosheets are attractive for energy storage and conversion. However, reliable and controllable synthesis of single- to few-layered TiS2 nanosheets is challenging due to the strong tendency of stacking and oxidation of ultrathin TiS2 nanosheets. This study reports for the first time the successful conversion of Ti3C2Tx MXene to sandwich-like ultrathin TiS2 nanosheets confined by N, S co-doped porous carbon (TiS2@NSC) via an in situ polydopamine-assisted sulfuration process. When used as a sulfur host in lithium-sulfur batteries, TiS2@NSC shows both high trapping capability for lithium polysulfides (LiPSs), and remarkable electrocatalytic activity for LiPSs reduction and lithium sulfide oxidation. A freestanding sulfur cathode integrating TiS2@NSC with cotton-derived carbon fibers delivers a high areal capacity of 5.9 mAh cm(-2) after 100 cycles at 0.1 C with a low electrolyte/sulfur ratio and a high sulfur loading of 7.7 mg cm(-2), placing TiS2@NSC one of the best LiPSs adsorbents and sulfur conversion catalysts reported to date. The developed nanospace-confined strategy will shed light on the rational design and structural engineering of metal sulfides based nanoarchitectures for diverse applications.