Mechanistic Insights into the Role of Covalent Triazine Frameworks as Cathodes in Lithium-Sulfur Batteries

Abstract

This study illuminates the applicability of covalent triazine frameworks (CTFs) as a potential cathode material in lithium-sulfur (Li−S) batteries. A systematic synthesis protocol is applied to generate a set of model CTFs containing covalently bound sulfur with varying porosities and conductivities. An in-depth structural characterization reconsiders the bonding motif of sulfur within the pore system. The model materials are electrochemically evaluated in coin cells. The CTF cathodes exhibit practically no cycling performance as a result of active material loss in carbonate-based electrolyte (≥200 mAh gsulfur−1 after 200 cycles). Moreover, in ether-based electrolytes the differentiation between sulfur transformation on the surface of the conductive additive and the (semi-)conducting CTF matrix is hardly feasible. Based on these results, the influence of the CTF material and the conductive additive with respect to sulfur utilization are discussed, demonstrating the critical role of this class of materials for application in Li−S batteries.