Ultrafine Ti3C2 MXene Nanodots-Interspersed Nanosheet for High-Energy-Density Lithium-Sulfur Batteries.

Nanostructured carbon materials have been extensively used for encapsulating sulfur and improving cyclic stability of lithium-sulfur (Li-S) batteries, but high carbon content and low packing density greatly limit their volumetric energy density. Herein, we present MXene-based Ti3C2T x (T x stands for the surface terminations) nanodots-interspersed Ti3C2T x nanosheet (TCD-TCS) to accomplish spatial immobilization and conversion of high-loaded sulfur species. Rich surface polar sites in TCD-TCS enhance structural integrity of the resultant electrode, while the absence of the carbon-based materials and conductive additives results in high tap density of the cathode materials. The TCD-TCS/S electrode exhibits an almost theoretical discharge capacity at a medium sulfur loading of 1.8 mg cm-2. Notably, ultrahigh volumetric capacity (1957 mAh cm-3) and high areal capacity (13.7 mAh cm-2) are synchronously achieved at a high sulfur loading of 13.8 mg cm-2. The mechanism study of sulfur evolution during discharge process highlights the importance of the integration of MXene-based nanodots and nanosheets in Li-S batteries. This proposed methodology holds great promise for the development of various high-performance energy storage materials.