Assessment of Li-S Battery Performance as a Function of Electrolyte-to-Sulfur Ratio

Lithium-Sulfur (Li-S) battery performance is greatly sensitive to cell design as a result of the highly complex reaction and shuttle mechanisms within the cathode. Electrolyte-to-sulfur (E/S) ratio is one of the key design parameters that have a great impact on the performance of Li-S batteries. Here, an integrated research methodology coupling experimental characterization and electrochemical modeling is applied to forecast the relation between the E/S ratio and the discharge capacity, cycling performance and cell- and system-level specific energy and energy density of the Li-S battery. The highest initial discharge capacity is achieved with an E/S ratio of 20 μ l mg −1 , whereas, the best capacity retention is observed for 13 μ l mg −1 . This experimentally obtained link between the E/S ratio and the discharge performance is taken into consideration in the proposed cell- and system-level performance models. Lower E/S ratios lead to higher battery performance at the cell and system level. Consequently, an E/S ratio of 13 μ l mg −1 presents the best performance as the impact of E/S ratio not only on the peak discharge capacity and capacity retention but also on the specific energy and energy density at the cell and system level are all considered.