AUTHOR=Lu Chengwei , Fang Ruyi , Wang Kun , Xiao Zhen , kumar G. Gnana , Gan Yongping , He Xinping , Huang Hui , Zhang Wenkui , Xia Yang 

TITLE=Supercritical CO2 Synthesis of Freestanding Se1-xSx Foamy Cathodes for High-Performance Li-Se1-xSx Battery

JOURNAL=Frontiers in Chemistry

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2021.738977

DOI=10.3389/fchem.2021.738977

ISSN=2296-2646

ABSTRACT=<p>Selenium-sulfur solid solutions (Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub>) are considered to be a new class of promising cathodic materials for high-performance rechargeable lithium batteries owing to their superior electric conductivity than S and higher theoretical specific capacity than Se. In this work, high-performance Li-Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub> batteries employed freestanding cathodes by encapsulating Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub> in a N-doped carbon framework with three-dimensional (3D) interconnected porous structure (NC@SWCNTs) are proposed. Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub> is uniformly dispersed in 3D porous carbon matrix with the assistance of supercritical CO<sub>2</sub> (SC-CO<sub>2</sub>) technique. Impressively, NC@SWCNTs host not only provides spatial confinement for Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub> and efficient physical/chemical adsorption of intermediates, but also offers a highly conductive framework to facilitate ion/electron transport. More importantly, the Se/S ratio of Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub> plays an important role on the electrochemical performance of Li- Se<sub>1-<italic>x</italic></sub>S<sub><italic>x</italic></sub> batteries. Benefiting from the rationally designed structure and chemical composition, NC@SWCNTs@Se<sub>0.2</sub>S<sub>0.8</sub> cathode exhibits excellent cyclic stability (632 mA h g−1 at 200 cycle at 0.2 A g<sup>−1</sup>) and superior rate capability (415 mA h g<sup>−1</sup> at 2.0 A g<sup>−1</sup>) in carbonate-based electrolyte. This novel NC@SWCNTs@Se<sub>0.2</sub>S<sub>0.8</sub> cathode not only introduces a new strategy to design high-performance cathodes, but also provides a new approach to fabricate freestanding cathodes towards practical applications of high-energy-density rechargeable batteries.</p>