High capacity polycarbazole-sulfur cathode for use in lithium-sulfur batteries

The potential use of electrochemically polymerized polycarbazole as an additive in lithium-sulfur battery cathodes has been investigated. Optimization of the polymer properties considered solvent, electrolyte and current-time profile during electropolymerization. It was found that electrodeposition from LiClO4-acetonitrile electrolyte and constant-potential deposition (at 1.15 V vs Ag/Ag+) gives the highest initial discharge capacity. This is most likely due to an optimum combination of specific surface area and conductivity. To improve the quality of the cathode, a slurry of carbon disulfide and dimethyl formamide was devised to balance the dispersion of carbon black and the solubility of sulfur. In 2032-coin cells, against a lithium anode, a polycarbazole-sulfur (PCBz-S) cathode with 30% sulphur showed the highest initial discharge capacity. A very good coulombic efficiency of around 98% and a capacity retention of over 91% for 50 charge/discharge cycles were obtained for the optimized PCBz-S cathode. Based on the cycling performance, PCBz is a potentially useful additive to mitigate the polysulfide shuttle effect. In addition, the electropolymerized carbazole matches the performance of a commercial polypyrrole that has been widely used as a conductive binder. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The potential use of electrochemically polymerized polycarbazole as an additive in lithium-sulfur battery cathodes has been investigated, showing promising initial discharge capacity and cycling performance through optimization of the electropolymerization process and formulation.