Gravimetric and volumetric energy densities of lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries receive considerable attention as a potential alternative to lithium-ion batteries (LIBs) due to their high theoretical gravimetric energy density (Eg). However, their volumetric energy density (Ev), which is also very important for practical applications is often neglected to emphasize their superior gravimetric energy density. In this review, we will try to provide a realistic and balanced perspective on the Ev of Li-S batteries. To calculate Ev, we establish a model based on a commercial pouch cell configuration, which allows one to evaluate the effect of various cell parameters. The requirements for Li-S batteries to be competitive against commercial LIBs in terms of Ev are proposed. Higher Ev for Li-S batteries could be expected by further balancing the sulfur loadings and sulfur utilization while reducing the electrode porosity as well as the amount of inactive additives in cathode. In particular, based on the calculated Ev values of recent works, we highlight the recent progress in both coin and pouch cells.