Enhancing the Charge Transportation Ability of Yolk-Shell Structure for High-Rate Sodium and Potassium Storage.
basic_science · Level V
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- Record sourced from PubMed, PMID 32250588.
- Also identified by DOI 10.1021/acsnano.9b10045.
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Abstract
The microstructure of large-capacity anodes is of great importance in determining the performance of sodium- and potassium-ion batteries. Yolk-shell nanostructures promise excellent structural stability but suffer from insufficient charge transfer rate during cycles. Herein, we tackle this challenge by constructing a single-walled carbon nanotube (SWNT) internally bridged yolk-shell structure, inside which SWNTs cover the surface of the yolk and connect the yolk and shell, for better electron/ion transportation. Combining the merits of both yolk-shell structure and conductive SWNT channels, the as-prepared Fe<sub>1-<i>x</i></sub>S/SWNT@C composite manifests high reversible capacity and ultralong cycling stability up to 8700 cycles. Moreover, it displays the best rate capability (317 mA h g<sup>-1</sup> at 20 A g<sup>-1</sup> for Na<sup>+</sup> and 236 mA h g<sup>-1</sup> at 10 A g<sup>-1</sup> for K<sup>+</sup>) among the reported yolk-shell structures and iron-sulfide-based anodes thus far. The kinetic analysis and density functional theory calculations further reveal that the Fe<sub>1-<i>x</i></sub>S/SWNT heterointerface can effectively enhance the reversibility of K<sup>+</sup> storage and decrease the K<sup>+</sup> diffusion energy barrier, leading to excellent pseudocapacitive behavior and fast ion transportation for outstanding rate capability.