Carbon‐to‐sulfur ratio in the cell controls the discharge capacity, cycling performance and energy density of a lithium‐sulfur battery

Cell design is a compelling feature to attain lithium-sulfur (Li-S) batteries with superior performance and carbon-to-sulfur (C/S) ratio is a vital design parameter with a critical influence on the battery performance. Herein, the dependence of the Li-S battery performance on the C/S ratio is examined for various electrolyte-to-sulfur (E/S) ratios based on experimentally measured peak discharge capacities and cycling performance aside from the gravimetric and volumetric energy densities projected by the cell- and system-level performance models. C/S ratio has a great influence on the cycling performance and discharge capacity, particularly for cells with a limited amount of electrolyte. The Li-S cell having a C/S ratio of 2 and an E/S ratio of 13 μL mg−1 has provided the highest initial capacity in addition to the best capacity retention. Model predictions suggest that increasing C/S ratio worsens the battery metrics at the pack level, particularly at low E/S ratios. Assessment of the performance based on the energy density is highly important; the best battery performance at the system level is calculated for the Li-S battery with the lowest E/S and C/S ratios despite that a lower discharge capacity has been achieved with this cell.