Supercritical CO2 Synthesis of Freestanding Se1- x S x Foamy Cathodes for High-Performance Li-Se1- x S x Battery

Chengwei Lu; Ruyi Fang; Kun Wang; Zhen Xiao; G Gnana Kumar; Yongping Gan; Xinping He; Hui Huang; Wenkui Zhang; Yang Xia

doi:10.3389/fchem.2021.738977

Supercritical CO₂ Synthesis of Freestanding Se_{1- x} S _x Foamy Cathodes for High-Performance Li-Se_{1- x} S _x Battery

Front Chem. 2021 Jul 28:9:738977. doi: 10.3389/fchem.2021.738977. eCollection 2021.

Authors

Chengwei Lu¹, Ruyi Fang¹, Kun Wang¹, Zhen Xiao², G Gnana Kumar³, Yongping Gan¹, Xinping He¹, Hui Huang¹, Wenkui Zhang¹, Yang Xia¹

Affiliations

¹ College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou, China.
² Institute of Optoelectronic Materials and Devices, China Jiliang University, Hangzhou, China.
³ Department of Physical Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai, India.

Abstract

Selenium-sulfur solid solutions (Se_1-x S _x ) 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_1-x S _x batteries employed freestanding cathodes by encapsulating Se_1-x S _x in a N-doped carbon framework with three-dimensional (3D) interconnected porous structure (NC@SWCNTs) are proposed. Se_1-x S _x is uniformly dispersed in 3D porous carbon matrix with the assistance of supercritical CO₂ (SC-CO₂) technique. Impressively, NC@SWCNTs host not only provides spatial confinement for Se_1-x S _x 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_1-x S _x plays an important role on the electrochemical performance of Li- Se_1-x S _x batteries. Benefiting from the rationally designed structure and chemical composition, NC@SWCNTs@Se_0.2S_0.8 cathode exhibits excellent cyclic stability (632 mA h g-1 at 200 cycle at 0.2 A g^-1) and superior rate capability (415 mA h g^-1 at 2.0 A g^-1) in carbonate-based electrolyte. This novel NC@SWCNTs@Se_0.2S_0.8 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.

Keywords: Li-Se1-xSx batteries; N-doped carbon foam; Se1-xSx; high areal capacity; supercritical CO2.