Effect of Carbon and Binder on High Sulfur Loading Electrode for Li-S Battery Technology

For the Lithium-Sulfur (Li-S) battery to be competitive in commercialization, it is requested that the sulfur electrode must have deliverable areal capacity > 8 mAh cm⁻², which corresponds to a sulfur loading > 6 mg cm⁻². At this relatively high sulfur loading, we evaluated the impact of binder and carbon type on the mechanical integrity and the electrochemical properties of sulfur electrodes. We identified hydroxypropyl cellulose (HPC) as a new binder for the sulfur electrode because it offers better adhesion between the electrode and the aluminum current collector than the commonly used polyvinylidene fluoride (PVDF) binder. In combination with the binder study, multiple types of carbon with high specific surface area were evaluated as sulfur hosts for high loading sulfur electrodes. A commercial microporous carbon derived from wood with high pore volume showed the best performance. An electrode with sulfur loading up to 10 mg cm⁻² was achieved with the optimized recipe. Based on systematic electrochemical studies, the soluble polysulfide to insoluble Li₂S₂/Li₂S conversion was identified to be the major barrier for high loading sulfur electrodes to achieve high sulfur utilization.