Ultrafine Ti<sub>3</sub>C<sub>2</sub> MXene Nanodots-Interspersed Nanosheet for High-Energy-Density Lithium-Sulfur Batteries.

Xiao, Zhubing; Li, Zhonglin; Li, Pengyue; Meng, Xueping; Wang, Ruihu · ACS Nano · 2019

basic_science · Level V

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Abstract

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 Ti<sub>3</sub>C<sub>2</sub>T <sub>x</sub> (T <sub>x</sub> stands for the surface terminations) nanodots-interspersed Ti<sub>3</sub>C<sub>2</sub>T <sub>x</sub> 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<sup>-2</sup>. Notably, ultrahigh volumetric capacity (1957 mAh cm<sup>-3</sup>) and high areal capacity (13.7 mAh cm<sup>-2</sup>) are synchronously achieved at a high sulfur loading of 13.8 mg cm<sup>-2</sup>. 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.