Covalent Triazine Frameworks Incorporating Charged Polypyrrole Channels for High-Performance Lithium–Sulfur Batteries

Abstract

Organosulfur polymers have emerged as promising electrode materials for lithium−sulfur (Li−S) batteries, mainly because of their ability to incorporate and stabilize high sulfur content. The low ionic and electronic conductivity of these polymers, however, limit their cycling performance at high active mass loadings. Moreover, Li−polysulfide (Li−PS) shuttling, a fatal phenomenon in the cyclability of Li−S batteries, can be mitigated via the entrapment of Li−PS by utilizing various supramolecular interactions. Herein, we report a new approach that incorporates one-dimensional charged polypyrrole into a two-dimensional covalent triazine framework (cPpy-S-CTF) synthesized in the presence of elemental sulfur. The cPpy-S-CTF enabled sulfur loadings up to 83 wt %, thanks to the perfluoroaryl-elemental sulfur SN Ar chemistry. Notably, the addition of charged polypyrrole, cPpy, triggered a 3D nanochannel formation in the cPpy-S-CTF with high-affinity anchoring sites toward Li−PS, while achieving decent ionic and electronic conductivity. The cPpy-S-CTF showed a remarkable electrochemical performance with a specific capacity of 1203.4 mA h g −1 at 0.05 C, an initial Coulombic efficiency of 94.1%, and a capacity retention of 86.8% after 500 cycles. These results point to the fact that the incorporation of charged conducting polymers could be a universal strategy to boost the electrochemical performance of organosulfur polymers in Li−S batteries.

The Prospect of Dimensionality in Porous Semiconductors

“…It should, however,b en oted that imparting af ramework materialo rc omposite with electrical conductivity also significantly enhances the overall performance as ac athode material, which wasrecently shown by Coskunand co-workers. [35] Especially fore lectronic applications, uniform surfaces/interfaces are preferred over polycrystalline powders to reduce losses originating from structural defects andg rain boundaries. Yet, am ajority of frameworks are obtained as polycrystalline powders of different particle sizes and are pressed to pelletst o conductc onductivity measurements.…”

Supramolecular Self‐Assembled Multi‐Electron‐Acceptor Organic Molecule as High‐Performance Cathode Material for Li‐Ion Batteries

“…So far, a number of diverse structural motifs have been investigated as organic cathode materials in rechargeable LIBs, namely, conjugated polycarbonyl compounds, [7][8][9][10][11] conducting polymers, [12] persistent radical derivatives, [13][14][15] organosulfur derivatives, [16][17][18][19] and redox-active heterocycles, [20][21][22] which have particularly shown great promise. However, in most organic electrodes, issues associated with low electronic conductivity and material dissolution in typical organic solvents, used in electrolytes alongside lithium salt, generally result in poor cycling performance, rapid capacity fading as well as low Coulombic efficiency.…”

Intrinsically conducting polymers and their combinations with redox-active molecules for rechargeable battery electrodes: an update

“…0.034% capacitance loss per cycle were observed during 1900 cycles. Channels established by PPy in a sulfur-rich triazine framework contributed to 86.8% capacity retention after 500 cycles of this positive electrode material (Kim et al 2020). Further concepts employing ICPs as encapsulating or restraining material to keep sulfur in place and restrict polysulfide movement have been reported (Ahn et al 2020;Chelladurai et al 2020;Díez et al 2020; Growing interest in using selenium instead of sulfur and combining this positive electrode material with other negative ones has resulted in similar considerations for, e.g., a sodium-selenium battery see (Zhang et al 2019c).…”