| Institution: | 1. Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Key Laboratory of High Performance Polymer-based Composites of Guangdong Province, GBRCE for Functional Molecular Engineering, School of Chemistry, Sun Yat-sen University, Guangzhou, 510006 China
These authors contributed equally to this work.;2. Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Key Laboratory of High Performance Polymer-based Composites of Guangdong Province, GBRCE for Functional Molecular Engineering, School of Chemistry, Sun Yat-sen University, Guangzhou, 510006 China;3. School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai, 519082 China;4. Guangdong-Hong Kong-Macau Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR, 999078 China |
| Abstract: | Here, we for the first time introduce ethoxylation chemistry to develop a new octupolar cyano-vinylene-linked 2D polymer framework (Cyano-OCF-EO) capable of acting as efficient mixed electron/ion conductors and metal-free sulfur evolution catalysts for dual-promoted Li and S electrochemistry. Our strategy creates a unique interconnected network of strongly-coupled donor 3-(acceptor-core) octupoles in Cyano-OCF-EO, affording enhanced intramolecular charge transfer, substantial active sites and crowded open channels. This enables Cyano-OCF-EO as a new versatile separator modifier, which endows the modified separator with superior catalytic activity for sulfur conversion and rapid Li ion conduction with the high Li+ transference number up to 0.94. Thus, the incorporation of Cyano-OCF-EO can concurrently regulate sulfur redox reactions and Li-ion flux in Li?S cells, attaining boosted bidirectional redox kinetics, inhibited polysulfide shuttle and dendrite-free Li anodes. The Cyano-OCF-EO-involved Li?S cell is endowed with excellent overall electrochemical performance especially large areal capacity of 7.5 mAh cm?2 at high sulfur loading of 8.7 mg cm?2. Mechanistic studies unveil the dominant multi-promoting effect of the triethoxylation on electron and ion conduction, polysulfide adsorption and catalytic conversion as well as previously-unexplored ?CN/C?O dual-site synergistic effect for enhanced polysulfide adsorption and reduced energy barrier toward Li2S conversion. |
